Symposium Organizers
David Horwat, Institut Jean Lamour-University de Lorraine
R. Mark Bradley, Colorado State University
Ulf Helmersson, Linköping Universitet
François Reniers, Université Libre de Bruxelles
NM05.01: Thin Films I
Session Chairs
Raul Gago
Judith MacManus-Driscoll
Monday PM, November 27, 2017
Hynes, Level 3, Room 313
9:00 AM - *NM05.01.01
Chromogenic Oxides Films—From Few Nanometers to Few Micrometers
Aline Rougier 1
1 , CNRS ICMCB, Pessac France
Show AbstractChromogenic materials are able to modulate their optical properties under an external stimulus including pressure, temperature, electrical field and so-on. Currently, there is a large demand to increase the functionality of chromogenic materials and devices in particular in the fields of energy, opto-electronics for emitting and sensing devices. Focusing our attention mostly on oxides, their chromogenic properties, were investigated by playing with the powder and film stoichiometry and morphology using various synthesis routes (including polyol route for powder, Sputtering, Doctor Blading, Sol gel,..) [1,2]. Herein, our approach will be illustrated through several examples mostly in the field of electrochromic and thermochromic materials. For instance, taking advantage of the multivalent nature of vanadium cations, multichromism of V2O5 thin (< 100 nm) and thick (> 1000 µm) films, in lithium and sodium based electrolytes will be demonstrated while the metal to insulator transition of VO2 powders will be discussed in respect of their optical and electrical properties. Finally, improved properties will be investigated by combining optimized materials characteristics and device architecture.
[1] A. Danine, L. Cojocaru, C. Faure, C. Olivier, T. Toupance, G. Campet, A. Rougier, Electrochimica Acta, 2014 129 113-119
[2] I. Mjejri, A. Rougier, M. Gaudon, Inorganic Chemistry, 2017, 56(3) 1734-1741.
9:30 AM - NM05.01.02
Tuning the Thermally Induced Sharp First-Order Semiconductor to Metal Transition In Epitaxial Vo2 Thin Films Grown by Pulsed Laser Deposition
Makhes Behera 1 , DHIREN PRADHAN 2 , Sangram Pradhan 1 , Aswini Pradhan 1
1 , Norfolk State University, Norfolk, Virginia, United States, 2 Geophysical Laboratory, Carnegie Institute of Science, Washington, DC, District of Columbia, United States
Show AbstractResearch and development on vanadium oxide (VO2) thin films has drawn significant interest in recent years because of their intriguing physical origin and a wide range of functionalities that are useful for many potential applications, including infrared imaging, smart windows, energy and information technologies. However, the synthesis of phase-stabilized materials, especially in epitaxial VO2 thin film forms, has remained a challenging task. We report the structural and electronic properties of high quality single crystalline thin films of VO2 grown on c-axis oriented sapphire substrates by the pulsed laser deposition at different deposition pressures and temperatures followed by various annealing schedule. The X-ray diffraction studies carried out on all the samples confirm an epitaxial growth of the VO2 film as well as how the epitaxial nature of the films change with a variation in the growth conditions. Further studies carried out by annealing the samples also sheds light on as to how the peaks revealed before annealing are actually merged peak, one of which when suppressed by annealing results in a better SMT property for the films. Our results demonstrate that the annealing of epitaxial VO2 films enhances the Semiconductor to Metal Transition SMT to that of bulk VO2 transition. The effect of oxygen partial pressure during the growth of VO2 films creates a significant modulation of the SMT from around room temperature to as high as the theoretical value of 68 oC. We obtained a bulk order transition ≥104 while reducing the transition temperature close to 60 oC, significantly less than of the theoretical value of 68 oC, demonstrating a clear and drastic improvement in the SMT switching characteristics. The transmission spectra measured using a UV-Vis Spectrometer also confirms the decrease in the transition temperature from a theoretical value of 68OC to ~60OC along with revealing the property of VO2 thin films to be transparent to the Near IR Spectrum at higher temperatures while maintaining the same transparency for the visible spectrum as in the lower temperature ranges. This property of VO2 opens the door for the thin films to be used as a coating material for smart windows that can selectively allow the IR waves depending on the temperature it is operated at. The results reported here, will open up the door for fundamental studies of VO2 along with the tuning of transition temperatures for potential applications in multifunctional devices.
# This work has been supported by NSF-CREST Grant number 1036494 and NSF-CREST Grant number 1547771.
9:45 AM - NM05.01.03
Enabling Exciton Tuning in Nanostructured EuOx Films by Plasma-Based Synthesis in Vacuum
Antonio Mariscal 1 , Aitana Tarazaga Martín-Luengo 2 , Adrian Quesada 3 , Alberta Bonani 2 , Jose Fernandez 3 , Javier Martin-Sanchez 2 , Rosalia Serna 1
1 , Laser Processing Group, Instituto de Opttica, IO-CSIC, Madrid Spain, 2 , Johannes Kepler Universität Linz, Linz Austria, 3 Instituto de Ceramica y Vidrio, ICV-CSIC, Madrid Spain
Show AbstractDue to its room temperature band-gap of 1.12 eV in bulk configuration [1] and to its compatibility with the technologically relevant semiconductors Si, GaAs and GaN [2][3], Europium monoxide (EuO) is a promising ferromagnetic semiconductor for the development of integrated spintronics and optical devices [4] . . However, EuO is highly unstable and tends to transform to the more stable Eu2O3. For this reason its synthesis with a suitable stoichiometry is challenging, and usually costly deposition techniques such as molecular beam epitaxy are employed [4]. This has hindered a widespread use of this relevant semiconductor, and its optical response and potential upon nanostructuration have been to-date scarcely investigated and exploited [5].
In this work we report the successful preparation of nanostructured EuOx thin films by a plasma based technique (pulsed laser deposition, PLD) using a non-conventional approach that consists in the in-situ reduction of a Eu2O3 bulk ceramic target by deposition in vacuum (10-7 mbar). Remarkably, our method allows achieving a fine-tuning of the oxygen content in the synthetized films by controlling the vacuum pressure in the chamber during the laser plasma generation. We demonstrate that the full range of film composition tuning: from EuO to Eu2O3 has been obtained. X-ray diffraction measurements show that the films are highly textured and are formed by nanocrystal grains with size in the 10 nm range. Spectroscopic ellipsometry measurements in the UV-VIS have been used to determine the nanostructured films band-gap and the magnetic exciton absorption values. Stoichiometric EuO films show properties similar to those of bulk EuO single crystals, however with a blue shift related to the stressed nanocrystalline structure. Further shift of the absorption edge to higher energies is achieved by increasing the oxygen content in the films. This successful plasma-reduction synthesis can be extrapolated to other plasma-based techniques, opening an inexpensive route for the synthesis of EuO as well as for other active functional oxides.
[1]A. Jayaraman, A.K. Singh, A. Chatterjee, S.U. Devi, Phys. Rev. B. 9 (1974) 2513–2520.
[2] A. Schmehl, V. Vaithyanathan, A. Herrnberger, S. Thiel, C. Richter, M. Liberati, et al., Nat. Mater. 6 (2007) 882.
[3] A.G. Swartz, J. Ciraldo, J.J.I. Wong, Y. Li, W. Han, T. Lin, et al., Appl. Phys. Lett. 97 (2010).
[4] D. V. Averyanov, Y.G. Sadofyev, A.M. Tokmachev, A.E. Primenko, I.A. Likhachev, V.G. Storchak, ACS Appl. Mater. Interfaces. 7 (2015) 6146.
[5] G.M. Prinz, T. Gerber, A. Lorke, M. Müller, Appl. Phys. Lett. 109 (2016).
10:30 AM - NM05.01.04
Pulsed Laser Deposition of In2O3-SnO2—From Films to Nano-Wires
Davide Del Gaudio 1 , Carl Boone 1 , Erica Mason 1 , Sneha Yarlagadda 1 , John Heron 1 , Ilan Shalish 2 , Rachel Goldman 1
1 , University of Michigan, Ann Arbor, Michigan, United States, 2 , Ben Gurion University, Beer Sheva Israel
Show AbstractAs micrometer sized device structures approach their limits in performance, nano-structures, such as nano-wires (NW) are being considered for next-generation high efficiency energy conversion and storage devices.[1] For example, metal oxides have been identified as promising materials for lithium ion batteries and UV lasers.[2] Furthermore, metal-oxide NWs have been embedded in field-effect transistors, lasers, solar cells, and various chemical sensors.[4] Typically, metal-oxide NW are prepared by vapor deposition[3] or thermal evaporation.[5] Recently, pulsed-laser deposition (PLD)[6][7][8] has emerged as a promising approach for the fabrication of tin-doped indium oxide (ITO), with film or NW growth often determined by the choice of a reactive (O2) or inert (N2) atmosphere.[6] To date, cubic NW with up to 10 atomic % Sn incorporated into In2O3 have been reported.[6][7][8] However, a mechanistic understanding of the influence of growth parameters and substrates on the morphology, composition, and crystal structure of the deposited film is needed. Additionally, PLD of various In2O3-SnO2 mixtures has yet to be considered. Therefore, we report on PLD of various In2O3-SnO2 mixtures onto c-plane sapphire, at various pressures, with various Sn/In ratios.We find a transition from vapor-liquid-solid to Volmer-Weber growth that is induced by increasing the pressure. In addition, as the Sn/In ratio is increased, the NW tip/stem contact angle decreases, thereby affecting the NW microstructure via liquid droplet capillary forces.[9] We will present high-resolution transmission electron microscopy (HRTEM) images and selective-area electron diffraction (SAED) patterns illustrating the structure and composition of the films, nanowires, and catalyst spheres. Cathodoluminescence measurements performed on NW of both composition will be discussed. Finally, we will discuss reactive PLD deposition of eutectic InSn alloy in oxygen atmosphere.
References
[1] Guo, Y.-G., Hu, J.-S., & Wan, L.-J. (2008) Advanced Materials, 20(15), 2878–2887
[2] Poizot, P., Laruelle, S., Grugeon, S., Dupont, L., & Tarascon, J.-M. (2000) Nature, 407(6803), 496–499
[3] Kong, Y. C. and Yu, D. P. and Zhang, B. and Fang, W. and Feng, S. Q. (2001) Applied Physics Letters, 78, 407-409
[4] Shen, G., Chen, P.-C., Ryu, K., & Zhou, C. (2009) J. Mater. Chem., 19(7), 828–839
[5] Yao, B. D. and Chan, Y. F. and Wang, N. (2002) Applied Physics Letters, 81, 757-759
[6] Khan, G. G., Ghosh, S., Sarkar, A., et. al. (2015) Journal of Applied Physics, 118(7), 074303
[7] Kee, Y. Y., Tan, S. S., Yong, T. K., et. al. (2012) Nanotechnology, 23(2), 025706
[8] Savu, R., & Joanni, E. (2006) Scripta Materialia, 55(11), 979–981
[9] Jacobsson, D., Panciera, F., Tersoff, J., Reuter, M.C., Lehmann, S. , Hofmann,, S. Dick, K.A., & Ross,, F.M. (2016) Nature 531, 317.
10:45 AM - NM05.01.05
Plasma-Enhanced Atomic Layer Deposition of MoS2—From 2D Monolayers to 3D Vertical Nanofins
Akhil Sharma 1 , Marcel Verheijen 1 , Vincent Vandalon 1 , Harm C.M. Knoops 2 1 , Ravi Sundaram 2 , Erwin Kessels 1 , Ageeth Bol 1
1 , Eindhoven University of Technology, Eindhoven Netherlands, 2 , Oxford Instruments, Yatton United Kingdom
Show AbstractPlasma-enhanced atomic layer deposition (PE-ALD) might prove as a key enabler for tackling the current challenge of large-area growth of 2-D materials with wafer level uniformity and digital thickness controllability. In this contribution, we have implemented PE-ALD to synthesize large-area MoS2 thin films with tuneable morphologies i.e. in-plane and vertically standing nano-scale architectures on CMOS compatible SiO2/Si substrates. The large scale 2D in-plane morphology has potential applications in nanoelectronics, while the 3D nanofin structures could be ideal for catalysis applications such as water splitting.
The PE-ALD process was characterized over a wide temperature range between 150°C - 450°C by using a combination of a metal organic precursor [C12H30N4Mo] as Mo source and a H2S + H2 + Ar (8 sccm + 2 sccm + 40 sccm) plasma as the co-reactant. The use of plasma species as reactants allowed for more freedom in processing conditions and for a wider range of material properties compared with the conventional thermally driven ALD. A saturated growth rate of ~0.9 Å/cycle was observed within the parameter space investigated. The number of layers in MoS2 film could be controlled accurately down to a mono-layer just by tuning the number of ALD cycles. The precise variation in thickness was confirmed by Raman spectroscopy which showed a monotonic decrease in the frequency difference value (Δk) between two vibrational modes for MoS2 with decreasing layer thickness down to 21 cm-1 which corresponds to a monolayer. The photoluminescence spectroscopy results were in line with these results, showing a strong peak at ~1.9 eV corresponding to the direct band gap transition for the mono-to-few layered MoS2. The chemical composition analysis by XPS showed that the MoS2 films grown were pure and stoichiometric in nature with negligible trace amounts of carbon and oxygen contaminants. The HAADF TEM analysis of the films grown at 450°C showed that during the initial ALD cycles, MoS2 islands expeditiously extended in the lateral direction and merged to form a film which continued to grow in a layer-by-layer fashion until a certain thickness. Thereafter, an out-of-plane vertical growth mode started to dominate as shown by cross-sectional TEM analysis. The origin of this transition from in-plane to out-of-plane growth mode might be attributed to the enhanced precursor adsorption on high surface energy locations such as grain boundaries, kinks or ledges. Due to crowding effects at these favourable adsorption sites subsequent vertical growth of MoS2 is observed.
These results show that plasma enhanced ALD might be instrumental in realizing not only the large area growth of high-quality 2-D materials but can also be applied as a tool to control the morphology of thin films which might yield into interesting structures (including heterostructures) for numerous opto-electronics and catalysis applications.
11:00 AM - *NM05.01.06
Plasma-Based Synthesis of Multifunctional Thin Dielectrics with Embedded Silver Nanoparticles—Study of the Interaction with Biological Targets
Kremena Makasheva 1
1 , LAPLACE, University of Toulouse, Toulouse France
Show AbstractNanomaterials and specifically nanocomposite thin layers became important components in bioanalytical devices, since they clearly enhance their performances in terms of sensitivity and detection limits down to single molecules. Plasma-based deposition processes can successfully come to the aid of synthesis of nanocomposite materials due to their strong versatility. However, rational engineering of nanocomposites, deposited in reactive plasmas, requires knowledge on the plasma behaviour in order to design the structural, optical and electrical properties of the deposits. It opens thus the way for transition from material level of development to system level of applications.
In this work we exploit the multifunctionality of silver nanoparticles (AgNPs) as plasmonic antenna when embedded at a controlled nanometric distance from the free surface of thin SiO2 layers and as biocide agents because of their strong toxicity towards microorganisms. The presentation will start with a description of the properties of an axially-asymmetric radiofrequency discharge sustained in reactive gas mixtures at low pressure used to prepare the plasmonic substrates. Special attention will be paid to the hybrid nature of this plasma process giving the opportunity to combine metal sputtering with plasma polymerization phase in order to obtain nanocomposite films. Diagnostic methods applied to control the deposition process, such as Optical Emission Spectroscopy, will be briefly discussed as well. In the following the structural and optical properties of these nanocomposite structures studied by Transmission Electron Microscopy (TEM) and ellipsometry will be exposed. The short-term toxicity of embedded AgNPs to photosynthesis of green algae was exploited to determine the bio-available silver release.
The “spectro-inside” concept, which consists of using AgNPs themselves as probes for amplifying and detecting optical signals of biological targets located in their vicinity, will be further presented. To that end very thin protein layers of Discosoma recombinant red fluorescent (DsRed) protein were deposited on the plasmonic structures. The Raman spectrum of the DsRed thin layers, not visible in absence of AgNPs, has been observed and analyzed owing to Surface Enhanced Raman Spectroscopy (SERS), making these AgNPs based nanocomposite substrates excellent candidates for bio-sensing applications.
11:30 AM - NM05.01.07
Fabrication of Three-Dimensional Nanocomposite Using Low-Dimensional Nanomaterials and Their Electrochemical Property for Energy Materials
Byeong-Joo Lee 1 2 , Sung-Il Jo 1 , Yoon-Jeong Chae 2 , Dong-Kyu Lee 2 , Chi Won Ahn 2 , Goo-Hwan Jeong 1
1 , Kangwon National University, Chuncheon Korea (the Republic of), 2 , National Nanofab Center, Daejeon Korea (the Republic of)
Show Abstract
Low-dimensional nanomaterials have attracted much attention due to its unique structure and outstanding physical properties such as high electrical conductivity, large surface area, and various chemical functionalities which realize the potential for future applications such as energy storage, electronics and sensors. In special, the electric double layer supercapacitors are considered as promising candidates for alternative energy storage systems due to their long cycle life and high rate capability at high power density. However, low energy density remains a key issue that must be addressed to expand applications and markets. Since the capacity of the electric double layer supercapacitor is determined by the surface area of electrode materials, development of the electrode material having a high specific surface area and a high electric conductivity such as onion-like carbons, carbonnanotubes, graphene and transition metal carbides and/or nitrides is required.
Here, we demonstrate the three-dimensional structured composite-based microsupercapacitor fabricated with carbon nanotubes and titanium carbides. The length controlled double-walled carbon nanotubes are synthesized by thermal chemical vapor deposition. Two-dimensional titanium carbide was prepared by selective interlayer etching of Ti3AlC2. The composite thin film was fabricated by sequential vacuum filtration using solutions of carbon nanotube and titanium carbide dispersed. The thin film was patterned by focused ion beam process to fabricate the microsupercapacitor and its electrochemical properties were measured. The effect of low-dimensional nanomaterial-based composite structures on the characteristics of the electric double layer supercapacitor was investigated.
11:45 AM - NM05.01.08
Plasmonic Effect of Sputtered Ag Nano-Particles on the Photovoltaic Characteristics of Si-Based Heterojunction Diode
Seda Kayra Güllü 1 2 3 , Hasan Güllü 4 3 , Mehmet Parlak 2 3 , Alpan Bek 2 3 5
1 Department of Applied Physics, Atilim University, Ankara Turkey, 2 Department of Physics, Middle East Technical University, Ankara Turkey, 3 Center for Solar Energy Research and Applications (GÜNAM), Middle East Technical University, Ankara Turkey, 4 Central Laboratory, Middle East Technical University, Ankara Turkey, 5 Micro and Nanotechnology, Middle East Technical University, Ankara Turkey
Show AbstractIn this study, the effect of the presence of plasmonic interface in the CdS-based p-Si heterojunction diode structure was investigated under the aim of attaining affordable enhancement in the cell performance. Plasmonic nano-layer has been point of interest to increase the absorbance of the active layer without increasing the thickness. In the photovoltaic device applications, light absorption by providing plasmon excitation and light localization inside the junction can be increased by embedding metal nanoparticles to the diode structure. The studied heterojunctions were fabricated by physical vapor deposition of CdS on one-side polished mono-crystalline p-Si wafers at room temperature. Ag was chosen as a highly conductive metal nanoparticle due to strong scattering of light characteristics which causes to increase the optical path length of incident photons in the active region. Therefore, in this work, Ag plasmonic layer was deposited on Si surface by magnetron sputtering technique and subsequently annealed to improve photovoltaic characteristics of the heterojunction diode. The effect of introducing plasmonic layer on the overall performance of the cell was studied in terms of the morphology, crystalline behavior, optical absorption and reflection, I-V characteristics. An enhancement in the photocurrent was observed in comparison with unmodified and Ag-modified p-Si surface from I-V measurements under AM 1.5 illumination. From these measurements, solar cell parameters as series resistance (Rs), open circuit voltage (Voc), short-circuit current (Isc), Fill Factor (FF) and efficiency (η) were determined under this plasmonic enhancement approach. Trapping of light was concluded as to be affordable method to enhance the photovoltaic characteristics by increasing the absorption and therefore generating more photocurrent.
Financial support from METU under BAP-08-11-2017-022 is gratefully acknowledged.
NM05.02: Thin Films II
Session Chairs
Raul Gago
Kremena Makasheva
Monday PM, November 27, 2017
Hynes, Level 3, Room 313
1:30 PM - *NM05.02.01
Radical Property Enhancements and New Multifunctionalities in Oxide Thin Films via a Nanocomposite Thin-Film Approach
Judith MacManus-Driscoll 1 , Rui Wu 1 , Seungho Cho 1 , Chao Yun 1 , Eun-Mi Choi 1 , Ahmed Kursumovic 1 , Aiping Chen 3 , Quanxi Jia 3 , Haiyan Wang 2
1 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom, 3 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractSince the discovery of high temperature superconductivity in perovskite oxides in 1986, the unearthing of a huge range of physical phenomena in transition metal oxides (TMOs) has been nothing short of remarkable, e.g. new magnetics, ferroelectrics, multiferroics, semiconductors, calorics, plasmonics, ionics, etc. The strong interplay of structural, electronic and magnetic degrees of freedom is critical for achieving the wide range of exciting properties, but it is very hard to control. While a huge amount of attention has been paid to understanding the exciting science originating from the different couplings, very little attention has been paid to engineering the materials to control the interplay of the degrees of freedom. Consequently, there are few applications today of these exciting materials. We have shown that the nanocomposite thin film approach is a powerful way forward to achieving control of the interplay, in a practical and simple way. This has enabled radical property enhancements to be achieved. This talk will review the achievements made, so far, in this field, highlighting some new results showing, for the first time, a practical converse magnetoelectric nanocomposite system with a large magnetoelectric coefficient at room temperature.
2:00 PM - NM05.02.02
Plasma Based Deposition of Functional Nanocomposites
Oleksandr Polonskyi 1 , Thomas Strunskus 1 , Mady Elbahri 2 , Franz Faupel 1
1 Chair for Multicomponent Materials, University of Kiel, Kiel Germany, 2 Nanochemistry and Nanoengineering, Department of Chemistry and Materials Science, Aalto University, Aalto Finland
Show AbstractNanocomposite films consisting of metal nanoparticles in a dielectric organic or ceramic matrix have unique functional properties with hosts of applications. The present talk demonstrates how plasma based vapor phase deposition techniques can be employed for tailoring the nanostructure and the resulting properties. Vapor phase deposition, inter alia, allows excellent control of the metallic filling factor and its depth profile as well as the incorporation of alloy nanoparticles with well-defined composition. The metallic nanoparticles typically form via self-organization during co-deposition of the metallic and matrix components due to the high cohesive energy of the metals and the low metal-matrix interaction energy. We have applied various methods such as sputtering, plasma polymerization, and evaporation for the deposition of the matrix component, while the metallic component has mostly been sputter-deposited or evaporated. Moreover, gas aggregation cluster sources were utilized to obtain independent control of filling factor and size of the embedded nanoparticles. In most applications, a high filling factor close to the percolation threshold is essential because the functional properties often require short range interaction between nanoparticles. Examples range from plasmonic composites through high frequency magnetic cores and sensors to biocompatible antibacterial coatings with tailored release rate.
2:15 PM - NM05.02.03
Non-Equilibrium Synthesis of Vertically Ordered Single Crystalline Oxide Nanobrush
Dongkyu Lee 1 , Xiang Gao 1 , Youngseok Jee 2 , Lisha Fan 1 , Erjia Guo 1 , Jonathan Poplawsky 1 , Thomas Farmer 1 , William Heller 1 , Kevin Huang 3 , Michael Fitzsimmons 1 , Matthew Chisholm 1 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , National Energy Technology Laboratory, Pittsburgh, Pennsylvania, United States, 3 Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractNanoscale structures and materials have attracted great interest over the last two decades owing to their physical properties or behaviors, which differ completely from those of their bulk counterparts. The fabrication of nanostructured materials requires using specialized methods and understanding growth mechanisms, and demand is growing for developing materials with vertically aligned geometries. As vertically aligned material systems offer many advantages, such as large length-to-width aspect ratio, high surface-to-volume ratio, and high density interfaces, a great number of opportunities can be realized by vertically aligned single crystalline nanomaterials. However, directed synthesis of such vertically aligned single crystalline nanostructures has been virtually unexplored. One of the main reasons is that while the formation of single crystalline phases requires a lot of heat to stabilize defect-free lattice structures, synthesis at a high temperature, close to or above the crystallization temperature of most oxide materials, usually promotes the surface diffusion of adatoms, forming a flat film. Therefore, achieving the ultimate control of this 2D oxide growth to construct 3D architectures has been extremely difficult, despite the enormous potential for technological breakthroughs.
In this presentation, we will present a completely new synthesis route to the formation of micron-long single-crystalline oxide nanobristles.1-2 Single crystalline nanostructures of either CeO2 or Y2O3, with a large porosity (up to ~50 %), were fabricated by pulsed laser epitaxy enabling a direct and template-free synthesis. This directed synthesis was made possible by growing oxide nanostructures under kinetically and thermodynamically balanced non-equilibrium conditions, far from the conventional growth conditions optimized for 2D thin films. Furthermore, we developed a completely new oxide nanoarchitecture, 3D nanosuperlattices with superior ionic conductivity by applying this new synthesis route. This development suggests the great potential of the pulsed laser epitaxy technique for design of functional oxide materials with precisely controlled morphologies and dimensions. In addition, due to the extremely large surface area and the increased interface density offered in these oxide nanostructures, many technological applications can be envisioned, including chemical sensors, fuel cells, membranes, and photovoltaic and electronic devices, in which a large contact area is critical for obtaining high efficiency and capacity.
1. D. Lee, X. Gao, L. Fan, E. Guo, T. O. Farmer, M. R. Fitzsimmons, M. F. Chisholm, and H. N. Lee, Adv. Mater. Interfaces 2017, 4, 1601034.
2. L. Fan, X. Gao, D. Lee, E. Guo, S. Lee, P. C. Snijders, T. Z. Ward, G. Eres, M. F. Chisholm, and H. N. Lee, Advanced Science, 2017, 1700045
* * This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
2:30 PM - *NM05.02.04
Phase Formation and Selectivity on Cr (co-)Doped TiO2 through Interface Engineering and Post-Deposition Flash Lamp Annealing
Raul Gago 1 , Slawomir Prucnal 2 , Javier Palomares 1 , Ignacio Jiménez 1 , R. Huebner 2
1 , Insituto de Ciencia de Materiales de Madrid (CSIC), Madrid Spain, 2 Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany
Show AbstractMany applications of TiO2 partially rely on its good performance as solvent for numerous impurities [1]. In particular, metal (cation) dopants have been used to functionalize or enhance TiO2 as catalyst [2], diluted magnetic semiconductor [3] or transparent conductor [4]. One of the most interesting properties of TiO2 relies on its photoactivity, exploited in many applications from catalysis, hydrogen production, pigments or solar cells [2]. However, TiO2 is mostly active in the ultraviolet (UV) region of the solar spectrum (band-gap > 3 eV) and there is a great interest in band-gap narrowing of TiO2 to achieve visible-light (VISL) response [2]. Metal doping do so and increases VISL absorption significantly but, unfortunately, introduces structural distortions in the host matrix that result in carrier recombination centers [5]. Apart from the structural quality, another relevant consideration on the production of doped TiO2 relies on the particular oxide matrix phase (anatase/rutile) [6]. For example, anatase has superior photoactivity than rutile although phase mixtures with high anatase content may present even higher photoactivity [7]. Therefore, special attention should also be devoted to the phase selectivity. Moreover, (heavily) doped TiO2 may display a completely different electronic structure that the pristine oxide material.
The aim of this study is to promote customized phase formation in Cr (co-)doped TiO2 films produced by magnetron co-sputtering. Special attention is paid to the structural arrangements around host and dopant sites from the X-ray absorption near-edge structure. We report the conditions driving to single- or mixed-phase formation with the novelty of exploring film architectures based on interface engineering and/or post-deposition flash-lamp annealing (FLA) [8]. The latter is a non-contact rapid thermal processing extensively used in Microelectronics but yet to be explored in the present context. Hence, FLA can be attractive for many industrial applications dealing with the synthesis of band-gap engineered TiO2-based materials.
REFERENCES:
[1] Sacerdoti et al., J. Solid State Chem. 177, 1781 (2004); [2] Henderson, Surf. Sci. Rep. 66, 185 (2011); [3] Matsumoto et al. Science 291, 854 (2001); [4] Furubayashi et al., Appl. Phys. Lett. 86, 252101 (2005); [5] Serpone et al., J. Phys. Chem. B 110, 24287 (2006); [6] Yang, et al., Phys. Rev. B 76, 195201 (2007); [7] Scanlon et al., Nat. Mater. 12, 798 (2013); [8] D. Reichel et al., Phys. Status Solidi C 9, 2045 (2012)
3:30 PM - NM05.02.05
Fracture Toughness Enhancement of Epitaxially Grown CrN/TiN Superlattice Thin Films
Rainer Hahn 1 2 , Matthias Bartosik 1 2 , Szilard Kolozsvári 3 , Hamid Bolvardi 4 , Paul Mayrhofer 1
1 Institute of Materials Science and Technology, Technische Universität Wien, Vienna Austria, 2 Christian Doppler Laboratory for Applied Oriented Coating Development, CDL-AOS at Technische Universität Wien, Vienna Austria, 3 , Plansee Composite Materials GmbH, Lechbruck am See Germany, 4 , Oerlikon Surface Solutions AG, Balzers Liechtenstein
Show AbstractCoherently grown nanolayered thin films, referred to as superlattice thin films, are known for their superior hardness as compared with their monolithically grown constituents. Recently we have shown –by employing in-situ micromechanical cantilever bending tests– that also the fracture toughness (in addition to the hardness) shows a significant bilayer period dependent behaviour *. While mechanisms based on dislocation activity explain the hardness-peak versus the bilayer-period, the linear elastic deformation of the micro-beams during the micro-fracture experiments suggests that these explanations are not directly applicable to describe the enhancement in fracture toughness. Consequently, an underlying, bilayer-period dependent intrinsic property has to be responsible for this behaviour. The present work represents a detailed experimental study of epitaxially grown CrN/TiN superlattice thin films with bilayer periods ranging from 4 to 160 nm deposited on MgO (100) substrates by unbalanced reactive magnetron sputtering. Possible explanations for the excellent mechanical properties, like peak hardness values of ~34 GPa and fracture toughness of ~3 MPa√m are discussed. The careful analysis of the experimental results unveils an excellent correlation between mechanical properties, interface constitution (e.g., interface width, misfit dislocations), and coherency strains.
* R. Hahn, M. Bartosik, R. Soler, C. Kirchlechner, G. Dehm, and P.H. Mayrhofer, Scr. Mat. 124, 67 - 70 (2016).
3:45 PM - NM05.02.06
High Quality Oxide Films Deposited at Room Temperature by Ion Beam Sputtering
Gerard Henein 1 , Juraj Topolancik 2
1 Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 , Roche Sequencing Solutions, Pleasanton, California, United States
Show AbstractThe highest quality oxides such as SiO2, Al2O3 and Indium Tin Oxide (ITO) require high temperature processing either during the growth of the film or annealing post-growth. Thermal SiO2 is grown at ≈1000 °C (1), ALD Al2O3 is deposited at ≈300 °C (2), and magnetron-sputtered ITO must be annealed above 350 °C in order to turn the film conductive (3). These elevated temperature requirements are not compatible with polymer substrates used for flexible electronics (4).
We have deposited dense and pinhole-free thin films of SiO2, Al2O3 and ITO at room temperature via ion beam sputtering. The deposition system consists of a 3-grid 14 cm RF ion gun directed at 200 mm targets of SiO2, Al and ITO. All three processes require a small flow of O2 to achieve stoichiometry. Typical conditions were: argon flow rate 3.3x10-7 m3/s, beam voltage 600 V, beam current 220 mA and acceleration voltage 150 V. The substrate wafers were kept at 20 °C. The base vacuum prior to deposition was 2.6x10-6 Pa.
The SiO2 films were 100 nm thick and measured by the mercury probe technique to obtain the C-V and I-V characteristics. The films were found to be of similar quality as thermal oxide with a resistivity of 10^14 Ω*m, breakdown field in excess of 7x10^8 V/m, and pinhole-free with an etch rate in 6:1 Buffered Oxide Etch (BOE) of 1.6 nm/s.
The Al2O3 films were part of a Pt- Al2O3-Pt vertical tunnel junction and were kept extremely thin, from 3 nm to 4 nm. The current-voltage characteristics of these junctions indicated a breakdown field roughly twice that achieved by ALD films for the same structure. This breakdown voltage was found to be independent of junction area, strongly suggesting the absence of pinholes in the film.
The ITO films were 50 nm to 100 nm thick. As deposited, they are fully transparent with an electrical resistivity of 5x10^-6 Ω*m.
In conclusion, the ion beam deposition technique has proven to be a powerful tool for the room temperature production of very high quality oxides, as thin as 3 nm. In addition, this process allows for a sub-nanometer control over the film thickness.
References
1. E.P. Eernisse, Appl. Phys. Lett. 35(1), 8 (1979)
2. Sun Jin Yun et al., J. Vac. Sci. Tech. 15, 2993 (1997)
3. Yalan Hu et al., Vacuum 75, 183-188 (2004)
4. “Flexible Electronics: materials and Applications”, William S. Wong, Alberto Salleo, 2009, ISBN 978-0-387-74362-2
4:00 PM - NM05.02.07
Structural and Mechanical Properties of Sputter Deposited Zr1-xMox Thin Films
Alejandro Borroto 1 2 , Stéphanie Bruyère 1 , Nicolas Thurieau 1 , Christine Gendarme 1 , Emilio Jimenez-Piqué 3 , Joan Roa 3 , Jean-Francois Pierson 1 , Frank Muecklich 2 , David Horwat 1
1 , Institut Jean Lamour, UMR CNRS 7198, University of Lorraine, Nancy France, 2 , Department of Materials Science and Engineering, Chair of Functional Materials, Saarland University, Saarbrücken Germany, 3 , Department of Materials Science and Engineering, Universitat Politecnica de Catalunya, Barcelona Spain
Show AbstractNano-crystalline and amorphous metallic alloys attract attention due to modified mechanical properties compared to micro-crystalline ones. Except for few cases, it is difficult to reach nano-crystalline and amorphous state in binary metal alloys using conventional metallurgy. In contrast, the cooling rates associated to the rapid transition from the vapor to the solid phase in sputter-deposited metallic alloys can be high enough to disable the crystallization of many systems. This fact can be used for the formation of amorphous and nano-crystalline structures and tailor the properties of so-produced metallic alloy films. These can exhibit high hardness (H) values while keeping an elastic modulus (E) characteristic of metals. The bonding state and, more particularly, the cohesive energy is also an important parameter within a strategy that aims at controlling the mechanical properties of nanostructured metals as it primarily determines their elastic behavior. From this point of view, Zr-based binary alloys designed on the basis of Mo addition are particularly interesting. First, the good ability of sputter-deposited Zr-based alloys to form amorphous and nano-crystalline structures can act in favor of the alloys hardening. Moreover, the intrinsic high hardness of Mo and the high cohesive energy of Mo and Zr among the transition metals make the Zr-Mo system a good candidate for hard metallic coatings with good elastic properties.
In this work Zr1-xMox thin films were deposited by co-sputtering in a wide range of compositions. For x ranging from 0.62 to 0.95 the sample structure is a nano-crystalline solid solution of Zr in the bcc lattice of Mo. For x values between 0.58 and 0.32, the sample structure is made of nano-crystalline Zr(Mo) clusters in an amorphous matrix. The coherence length deduced from X-ray diffractograms was found in the range 1 nm to 8 nm, depending on the composition. Mechanical measurements show that the films exhibit high hardness, low Young’s modulus and therefore high H/E ratio compared with the bulk Zr and Mo. The friction coefficient values were found low, consistent with the high values of the H/E ratio. Finally, an inverse Hall-Petch effect was observed for coherence length lower than 6 nm.
4:15 PM - NM05.02.08
Novel Ultra-High Temperature Ta-C and Ta-C-N Coatings—From Ab Initio Calculations to PVD Depositions
Thomas Glechner 1 , Stefan Fritze 2 , Erik Lewin 2 , Valentina Paneta 3 , Daniel Primetzhofer 3 , Szilard Kolozsvári 4 , David Holec 5 , Helmut Riedl 1 , Paul Mayrhofer 1
1 , TU Wien, Institute of Materials Science, Wien Austria, 2 Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala Sweden, 3 , Uppsala University, Department of Physics and Astronomy, Uppsala Sweden, 4 , Plansee Composite Materials GmbH, Lechbruck am See Germany, 5 , Montanuniversität Leoben, Department Physical Metallurgy and Materials Testing, Leoben Austria
Show AbstractIn the field of ultra-high temperature applications, the choice of materials is very limited due to the demanding requirement profile. Major characteristics are highest melting temperatures (TM > 3000 °C), single-phase structures as well as low tendency for recrystallization effects. These requirements are most likely fulfilled by refractory ceramics such as transition metal carbides (TMCs). Especially, the binary Ta-C as well as the ternary Ta-Hf-C systems are known for their outstanding thermal properties. However, the very brittle character of these materials (fracture appearance transition temperatures (FATT) of about 0.5 TM) is one major limiting factor for a wide usage as structural components. Therefore, the application of thin films synthesized by physical vapour deposition (PVD) is a highly attractive way to gain the outstanding thermal properties.
In this study, we used a computational guided approach to study in depth the influence of the deposition parameters on the structure and morphology, mechanical properties, as well as thermal stability of sputter deposited Ta-C and Ta-C-N thin films. To avoid the formation of amorphous C-containing phases all films were deposited using a TaC0.97 compound target. The carbon content within the coatings strongly correlates with the target-to-substrate alignment, the deposition temperature, as well as bias voltage applied. Hence, a variation of substoichiometric TaCy coatings between TaC0.65 and TaC0.96 is achieved, even when co-sputtering pure C to compensate the amount of vacant carbon. All these mainly fcc structured coatings show an ultra-high hardness behaviour with values between 42 to 46 GPa, also after aging them for 1 hour in inert atmosphere at 1000 °C. In relation to the as deposited composition as well as amount of C-C bonds small hexagonal Ta2C phase fractions can be observed. The most preferable composition in terms of temperature driven stabilization (verified up to 2400 °C) of defected structures is located in the range of TaC0.80.
In contrast to the stabilization of fcc structured TaCy by carbon vacancies, are for cubic rock-salt Ta1-x-yCxNy coatings also metal vacancies important. These theoretical predictions obtained by ab initio calculations could be confirmed by reactively sputtered Ta1-x-yCxNy thin films using various Ar/N2 gas mixtures. Nitrogen rich atmospheres lead to dual phase structured coatings obtaining supersaturated fcc Ta1-x-yCxNy as well as hexagonal Ta2N crystals. This observation is also reflected in the hardness evolution varying from 38 to 25 GPa from single to dual phase coatings.
4:30 PM - NM05.02.09
Designing Novel Boride Materials from Scratch
Vincent Moraes 1 , David Holec 1 , Hamid Bolvardi 2 , P. Polcik 3 , Helmut Riedl 1 4 , Paul Mayrhofer 1 4
1 , CDL-AOS @ TU Wien, Vienna Austria, 2 , Oerlikon Balzers Surface Solutions AG, Balzers Liechtenstein, 3 , Plansee Composite Materials GmbH, Lechbruck Germany, 4 Institute of Materials Science and Technology, TU Wien, Vienna Austria
Show AbstractThe increasing demand in various industrial applications calls for a target-driven development of protective coatings with exceptional properties. Therefore, transition metal nitrides have been studied and developed extensively. However, the exploration of new protective coating systems is required to meet upcoming challenges not only in machining applications.
A rather new promising class of materials – to be used as protective thin films – are borides. Especially, multinary borides are rather unexplored compared to their nitride based counterparts. The age hardening effect of Ti1-xAlxN, which can be prepared with largely supersaturated phases (a necessary prerequisite for age hardening), makes this to one of the most important material systems for thin film applications. The formation of coherent domains through spinodal decomposition (isostructural decomposition of supersaturated Ti1-xAlxN towards TiN- and AlN-rich domains) allows for significant strengthening effects at elevated temperatures (for example, as obtained during application). Transferring this concept of the highly successful Ti1-xAlxN system (where two nitride phases compete) to borides will allow developing new materials with outstanding properties, for which we used a semi-automated density functional theory (DFT) approach.
In this study, we investigated the ground state properties (energy of formation, lattice constants, bulk moduli) of two competing structures of transition metal diborides by DFT. The most promising combinations were realized to develop new ternary diborides by physical vapour deposition, which were investigated for their properties.
4:45 PM - NM05.02.10
Plasma-Assisted Atomic Layer Deposition of Nickel Carbide and Its Application for Supercapacitors
Xinwei Wang 1 , Wei Xiong 1 , Qun Guo 2 , Zheng Guo 1 , Qiang Chen 2 , Zhongwei Liu 2
1 School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen, Guangdong, China, 2 Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing, Beijing, China
Show AbstractNickel carbide (NiCx) is an intriguing material which has recently gained great attention for its potential applications in energy conversion systems. The synthesis of high-quality NiCx thin films is of particular importance for the energy applications; however, there are so far very few reports on the synthesis of NiCx thin films. Herein, we present a new synthesis method by using plasma-assisted atomic layer deposition (PAALD) to prepare high-quality NiCx thin films. The PAALD process employs a metal-organic Ni precursor along with hydrogen plasma to activate the reactivity. The process is able to deposit continuous, pure, smooth NiCx films with the film thickness well controllable by adjusting the total deposition cycles. Various characterizations, such as AFM, SEM, XPS, and TEM, are carefully performed on the deposited NiCx films, and an in-situ technique using quartz crystal microbalance (QCM) is also employed to monitor the PAALD process. Based these results, we propose the essential surface chemistry reactions for the film growth during the deposition. With optimized deposition conditions, the PAALD process is able to conformally coat NiCx thin films on high-surface-area electrodes with excellent film uniformity. The NiCx-coated electrodes exhibit remarkable electrochemical redox performance. We further demonstrate that the PAALD prepared NiCx electrodes are highly promising for supercapacitor applications.
Symposium Organizers
David Horwat, Institut Jean Lamour-University de Lorraine
R. Mark Bradley, Colorado State University
Ulf Helmersson, Linköping Universitet
François Reniers, Université Libre de Bruxelles
NM05.03: Nanopatterning by Ion Beams and Plasmas
Session Chairs
R. Mark Bradley
Carsten Ronning
Tuesday AM, November 28, 2017
Hynes, Level 3, Room 313
8:00 AM - *NM05.03.01
The Soft Mode Plays a Role in Defect Persistence in Pattern-Forming Systems
Patrick Shipman 1 , Francis Motta 2 , R. Mark Bradley 1
1 , Colorado State University, Fort Collins, Colorado, United States, 2 , Duke University, Durham, North Carolina, United States
Show AbstractWhen the surface of a nominally flat binary material is bombarded with a broad, normally incident ion beam, disordered hexagonal arrays of nanodots can form. Defects, such as dislocations in ripple patterns or penta-hepta pairs in hexagonal arrays, limit the utility of patterns produced by ion bombardment. We show that a neutrally stable soft mode can contribute to the persistence over time of defects that form in the early stages of pattern formation. Topological measures of order provide a method for determining if a defect is removed as the pattern evolves.
8:30 AM - NM05.03.02
Structure and Plasmonic Properties of Ag Nanostructures under Ultra-Low-Energy Ion Bombardment
David Babonneau 1 , Florian Chabanais 1 , Lionel Simonot 1 , Sophie Rousselet 1 , Sophie Camelio 1
1 , CNRS, Futuroscope France
Show AbstractRecent applications of nanostructures with tunable plasmonic properties (e.g. in nanoscale photonics, photovoltaics, imaging, sensing, biology and medicine, etc.) demand a full control of their surface-plasmon-resonance (SPR) characteristics such as energy, width and amplitude. Therefore, fabrication of nanostructures using controlled growth and reactivity processes is highly desirable to tune their morphology (size and shape), organization and composition. While the SPR can be tailored by post-fabrication treatments such as thermal annealing or exposure to reactive gas atmospheres, it has recently been shown that the plasmonic response of noble metal nanoparticles grown by physical vapor deposition can also be modified by ultra-low-energy ion bombardment (< 100 eV, i.e. near the sputtering threshold) [Antad et al., Nanotechnology 24, 045606 (2013); J. Nanopart. Res 16, 2328 (2014)]. Indeed, ion-induced soft-sputtering associated with enhanced Ag mobility result in progressive but irreversible changes of both the morphology and organization of the nanoparticles, which cause a blue-shift together with an amplitude decrease and a narrowing of the SPR band. In this work, we focus on the evolution of percolated Ag films and of self-assembled Ag nanoparticle chains under bombardment with ultra-low-energy Ar ions. Percolated Ag films were grown on silicon nitride buffer-layers by magnetron sputtering deposition whereas self-assembled Ag nanoparticle chains were prepared by glancing-angle deposition onto pre-patterned rippled alumina surfaces [Camelio et al., Nanotechnology 25, 035706 (2014)]. By combining post-mortem structural characterizations (HAADF-STEM) and real-time optical measurements (Surface Differential Reflectance Spectroscopy), we show that the broadband character of the percolated films gradually moves towards narrow SPR bands arising from the formation of disconnected irregularly-shaped nanoparticles that later evolve into isolated spherical nanoparticles. Regarding the structural evolution of the self-assembled Ag nanoparticle chains (characterized by a bimodal distribution including isolated spheroidal nanoparticles and strongly coupled self-aligned nanorods), our observations show that ultra-low-energy ion bombardment induces a preferential sputtering of the isolated spheroidal nanoparticles as well as a progressive increase of the nanometer gaps between neighboring nanorods. The dichroic character of the resulting plasmonic nanostructures, which can be used for biosensing applications, can thus be finely modulated by modifying the coupling between particles. In addition, the kinetics of ion-induced modifications can be easily controlled by varying the ion energy and ion flux. Therefore, we demonstrate that ultra-low-energy ion bombardment could emerge as an efficient alternative to more traditional thermal annealing treatments for tuning the plasmonic properties of nanostructures with great flexibility.
8:45 AM - NM05.03.03
Unraveling Atomic-Level Self-Organization at the Plasma-Material Interface
Jean Paul Allain 1 , Akshath Shetty 1
1 , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractThe intrinsic dynamic interactions at the plasma-material interface and critical role of irradiation-driven mechanisms at the atomic scale during exposure to energetic particles require a priori the use of in-situ surface characterization techniques [1]. Characterization of “active” surfaces during modification at atomic-scale levels is becoming more important as advances in processing modalities are limited by an understanding of the behavior of these surfaces under realistic environmental conditions. Self-organization from exposure to non-equilibrium and thermalized plasmas enable dramatic control of surface morphology, topography, composition, chemistry and structure yielding the ability to tune material properties with an unprecedented level of control. Deciphering self-organization mechanisms of nanoscale morphology (e.g. nanodots, ripples) and composition on a variety of materials including: compound semiconductors, semiconductors, ceramics, polymers and polycrystalline metals via low-energy ion-beam assisted plasma irradiation are critical to manipulate functionality in nanostructured systems.
By operating at ultra-low energies near the damage threshold, irradiation-driven defect engineering can be optimized and surface-driven mechanisms controlled. Tunability of optical, electronic, magnetic and bioactive properties is realized by reaching metastable phases controlled by atomic-scale irradiation-driven mechanisms elucidated by novel in-situ diagnosis coupled to atomistic-level computational tools. In this work we present data in-operando the mechanisms responsible for low-energy (250-1000 eV) Ar, Kr and Ne irradiation of III-V semiconductors and Si nanopatterning. We conduct measurements of surface composition and chemistry with environmental XPS and illustrate the importance of in-operando and in-situ characterization of the surface and sub-surface regions from first ML down to about 10-nm. High-pressure low-energy ion scattering spectroscopy and mass spectrometry are also combined to elucidate mass redistribution and ion-induced desorption mechanisms at play during nanostructuring. Additional examples including ZnO nanoparticles on PDMS and nanopatterning of 70-nm TiO2 thin films on biosensors are presented to illustrate in-situ PMI techniques.
1. J.P. Allain and A. Shetty, J. Phys. D: Appl. Phys, Topical Review, 2017
9:00 AM - NM05.03.04
Terraced Topographies and Blazed Diffraction Gratings Produced by Ion Sputtering
R. Mark Bradley 1 , Matt Harrison 1 , Daniel Pearson 1
1 , Colorado State University, Fort Collins, Colorado, United States
Show AbstractBombarding a solid surface with an obliquely-incident, broad ion beam can lead to the emergence of surface ripples with wavelengths as short as 10 nanometers. The anisotropic Kuramoto-Sivashinsky (AKS) equation has been used to model the formation of these ripples for more than two decades. However, when the angle of incidence is large, intriguing phenomena are observed that are not reproduced by the AKS equation. We have introduced an equation of motion for the surface of an ion-bombarded material that differs from the AKS equation by the inclusion of a cubic nonlinearity [1]. This additional nonlinear term results from an improved approximation to the sputter yield. We have shown that this term can have a crucial influence on the dynamics --- it can lead to the formation of a terraced topography that coarsens in time, in accord with experimental observations for high incidence angles. Our simulations establish that regular terraced surfaces produced by bombarding a surface with a sinusoidal pre-pattern could serve as highly efficient blazed diffraction gratings [2]. In turn, when ion-assisted deposition of layers of alternating composition is carried out with a regular terraced surface as the substrate, the result can be a high quality multilayer blazed grating suitable for use in the extreme ultraviolet or soft X-ray regime [3].
1. D. A. Pearson and R. M. Bradley, J. Phys.: Cond. Matt. 27, 015010 (2015).
2. M. P. Harrison and R. M. Bradley, J. Appl. Phys. 121, 054308 (2017).
3. M. P. Harrison and R. M. Bradley, J. Appl. Phys. 121, 225304 (2017).
10:00 AM - *NM05.03.06
Nanoscale Surface Patterning of Crystalline Semiconductor Surfaces by Broad Ion Beam Irradiation
Stefan Facsko 1 , Xin Ou 2 , Martin Engler 1 , Denise Erb 1 , Tomas Skeren 3 , R. Mark Bradley 4
1 Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany, 2 Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai China, 3 , IBM Research - Zürich, Rüschlikon Switzerland, 4 Department of Physics, Colorado State University, Fort Collins, Colorado, United States
Show AbstractVarious self-organized nanoscale surface patterns can be produced by low- and medium-energy ion beam irradiation [1], depending on the irradiation conditions. Hexagonally ordered dot or pit patterns, checkerboard patterns, as well as periodic ripple patterns oriented perpendicular or parallel to the ion beam direction are formed spontaneously during the continuous surface erosion by ion sputtering. On amorphous surfaces, the formation of these patterns results from an interplay of different roughening mechanisms, e.g. curvature dependent sputtering, ballistic mass redistribution, or altered surface stoichiometry on binary materials, and smoothing mechanisms, e.g. surface diffusion or surface viscous flow.
An additional surface instability arises above the recrystallization temperature of the material. In this case, ion induced bulk defects are dynamically annealed and amorphization is prevented. The diffusion of ion-induced vacancies and ad-atoms on the crystalline surface is now affected by the Ehrlich-Schwoebel (ES) barrier, i.e. an additional diffusion barrier to cross terrace steps. Vacancies and ad-atoms are trapped on terraces and can nucleate to form new extended pits or terraces, respectively [2].
For the description of the pattern formation and evolution in the reverse epitaxy regime, a continuum equation can be used which combines the ballistic effects of ion irradiation and effective diffusion currents due to the ES barrier on the crystalline surface. By comparison with experimental studies of pattern formation on Ge and GaAs surfaces at different angles and temperatures, we will show that the pattern evolution is determined by the combined action of surface instability due to the ES barrier, surface diffusion, and ballistic effects of ion irradiation.
[1] A. Keller and S. Facsko, Materials 3, 4811 (2010).
[2] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).
10:30 AM - NM05.03.07
Formation of Electrical Copper Patterns by Copper Complex Decomposition upon Plasma Exposure
Yousef Farraj 1 , Shlomo Magdassi 1
1 , Hebrew University of Jerusalem, Jerusalem Israel
Show AbstractIn the past decade, the formation of electrical circuits by direct printing of conductive ink has gained high interest as it enables simple fabrication of devices such as circuit boards, RFID tags, touch screens and flexible displays. The most common conductive inks are based on silver nanoparticles. However, their high cost limits the fabrication of low cost plastic devices and therefore, a major challenge in this field is to find replacement inks which are based on low cost metals. Copper is the most promising candidate, having the second lowest resistivity of metals, and its cost is about 90 times lower than that of silver. Nevertheless, the main obstacle in utilizing inks containing copper nanoparticles is the rapid oxidation of the particles before and after printing.
Here we describe the formation and utilization of a copper complex ink that undergoes decomposition to yield copper nanoparticles upon exposure to plasma treatment. The ink is stable in ambient conditions for prolonged periods, without any deterioration of its functionality, as compared to what is usually encountered in nanoparticles based inks, such as aggregation and formation of copper oxide. The complex decomposition and formation of copper particles were investigated by a variety of analytical tools, and printed patterns has a conductivity as high as 23% of bulk copper.
10:45 AM - NM05.03.08
Fabrication of Complex Nanostructures Using Hole-Mask Colloidal Lithography
María Salazar 1 , Vladimir E. Bochenkov 1 , Aske Jørgensen 1 , Duncan Sutherland 1
1 , Aarhus University, Aarhus Denmark
Show AbstractHole-mask colloidal lithography is a feasible fabrication technique of metallic nanostructures over large areas, which involves self-organization of colloidal particles on a thin PMMA layer to perform a sacrificial mask, from which nanostructures are created by physical vapor deposition [1]. Nanostructures fabrication designs are limited due to its formation principle where the inclination of sample is necessary [2]. In order to extend the range of possible patterns that can be fabricated and their potential applicability we have created an atomic version of a pinhole camera using hole-mask colloidal lithography. In our design, we add a structured intersection mask with a target shape in the micrometer scale to obtain a replica of the pattern in nanometer scale.
Previously nanolithography based on an atom pinhole camera has been demonstrated [3], but nanoscale membranes manufactured by the method of ion beam milling are required, restricting the fabrication of nanostructures to a small area. In this work, we have created colloidal hole-masks based on self-assembly with thick PMMA layers to avoid the use of membranes allowing nanostructures fabrication over large areas. Traditional hole-mask colloidal lithography typically works with thin PMMA layers around 200 nanometers in thickness. In this work, we use PMMA layers of several micrometers thickness, we have modified etching conditions increasing the power and decreasing process pressure to create a thick hole-mask.
We also demonstrate that a thicker PMMA hole-mask layer permits the fabrications of dimer pairs better, conserving the circular disk shape via an almost normal incidence deposition of material through the holes. Fabrication of disk dimers with thin PMMA hole-mask layers requires a significant change of angle, creating elliptical shaped structures. Our experiments demonstrated that the change of angle related to PMMA layer thickness can cause shape distortion.
By modifying hole-mask characteristics and adding an intersection mask, we have developed a novel fabrication route to achieve nanostructures with a complex design over large areas for a broad range of future applications.
[1] H. Fredriksson, Y. Alaverdyan, A. Dmitriev, C. Langhammer, D.S.Sutherland, M. Zäch and B. Kasmeo “Hole-Mask Colloidal Lithography” Advanced Materials 19:23 4297- 4302 (2007).
[2] M. Frederiksen and D.S. Sutherland “Direct modification of colloidal hole-masks for locally ordered hetero-assemblies of nanostructures over large areas” Nanoscale 6:2 731-735 (2014) DOI: 10.1039/c3nr03871h.
[3] P N Melentiev, A V Zablotskiy, D A Lapshin, E P Sheshin, A S Baturin and V I Balykin “Nanolithography based on an atom pinhole camera” Nanotechnology 20 235301 (2009).
11:00 AM - NM05.03.09
FIB-Induced Droplet Formation and Motion
Joshua Stout 1 , Jonathan Freund 1 2 , Harley Johnson 1
1 Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractNanoscale fabrication using a focused ion beam (FIB) seems to depend upon a balance of multiple physical mechanisms. In a FIB process, charged ions with kinetic energies of 1keV-50keV are accelerated towards a target surface where they can cause sputtering or localized boiling. Though high energy FIBs can be effective and fast, low energy FIB is often preferred for precision or minimizing collateral damage. For FIB energies near 1keV, the sputter yield is low, so more incident ions are required to remove target material. It has been observed that when some threshold ion dose is exceeded, new nanostructures begin to form. Since low energy ions have a limited penetration depth, these new surface nanostructures may serve as barriers that inhibit further removal of the target material. Understanding the mechanisms behind the formation and motion of these nanostructures is important in optimizing the overall FIB process. We consider III-V materials, such as GaAs or AlAs. Sputtering is anticipated to be important, but our focus is on whether or not structures may form due to the accumulation of incident ions. We extend a sputtering model to include atomic motion driven by a composition dependent chemical potential. For the particular case of liquid droplet formation, we combine a lubrication model for droplets with a Cahn-Hilliard type model for chemical diffusion and phase separation. By implementing the preferential sputtering model as a boundary condition, this continuum model is used to illustrate the formation and subsequent motion of FIB-induced surface droplets. This model produces results that are consistent with our general observations from ∼50ns molecular dynamics with ∼50,000 target atoms and ∼5,000 ion impacts, and is extendable to long timescales. These results at the longer timescale are then compared with observations made experimentally.
11:15 AM - NM05.03.10
Fabrication, Microstructure and Advanced Electron Emission Applications of Vertically Aligned Nitrogen-Doped Nanocrystalline Diamond Nanorods
Kamatchi Sankaran 1 2 , Svetlana Korneychuk 3 , Sujit Deshmukh 4 , K. Srinivasu 5 , Sien Drijkoningen 1 2 , Paulius Pobedinskas 1 2 , Gourav Bhattacharya 4 , J. Verbeeck 3 , Marlies Van Bael 1 2 , Susanta Roy 4 , I-Nan Lin 6 , Ken Haenen 1 2
1 Institute for Materials Research (IMO), Hasselt University, Diepenbeek Belgium, 2 IMOMEC, imec, Diepenbeek Belgium, 3 , University of Antwerp, Antwerp Belgium, 4 , Shiv Nadar University, Gautam Buddha Nagar India, 5 , National Tsing Hua University, Hsinchu Taiwan, 6 , Tamkang University, Tamsui Taiwan
Show AbstractDiamond is a good candidate for solid-state electron emitters because of its negative electron affinity (NEA) surface when hydrogen terminated, in addition to superior properties such as mechanical hardness, chemical inertness and high thermal conductivity [1]. Significant applications may be enabled with the development of a stable electron emission source that operates at low applied fields, or a thermionic source that would operate at low temperatures. Specifically, the development of high current field emission cathodes would be important for microwave systems that would exhibit effectively instant-on characteristics. Low temperature thermionic emission could enable the development of compact and highly efficient heat to electrical energy conversion systems, which could prove important for large scale commercial energy systems and remotely operated compact systems.
The focus of this work is on the development and field electron emission behavior of vertically aligned nitrogen-doped nanocrystalline diamond nanorods (N-DNRs) and their subsequent thermionic behaviour. N-DNRs were fabricated from nanocrystalline diamond films by reactive ion etching using nanodiamond particles serving as a hard mask [2]. The resulting nanorods have diameter and height in the respective ranges of ~ 15-20 nm and ~ 800-1200. The superior field emission behaviour of the nanorods compared to flat films is characterized by a low turn-on field (5.26 V/mm), a long lifetime stability (700 min), and a large field enhancement factor (3270). These values can also be advantageous in a thermionic energy converter. The thermionic emission measurements from the nanorods resulted in a high current density of 16 mA/cm2 at a temperature of 550° C. The enhanced field/thermionic emission properties are attributed to the nanocomposite nature of the nanorods composed of sp2-graphitic phases present in the boundaries between the nano-sized diamond grains, as evidenced by a combination of Raman spectroscopy and advanced transmission electron microscopy. The simplicity of the fabrication process of these N-DNRs may have great potential for cathode applications in field emission displays and thermionic energy converters.
K.J. Sankaran and P. Pobedinskas are Postdoctoral Fellows of the Research Foundation-Flanders (FWO).
References:
[1] R.J. Nemanich, J.A. Carlisle, A. Hirata, K. Haenen, MRS Bulletin 39/6 (2014), 490-494.
[2] K.J. Sankaran, C.J. Yeh, S. Drijkoningen, P. Pobedinskas, M.K. Van Bael, K.C. Leou, I.N. Lin, K. Haenen, Nanotechnology 28/6 (2017), 065701.
11:30 AM - *NM05.03.11
Ion Beam Doping of Semiconductor Nanowires
Carsten Ronning 1
1 , University of Jena, Jena Germany
Show AbstractSemiconductor nanowires are of major importance within the area of nanotechnology, and are usually synthesized using the so-called vapor-liquid-solid (VLS) growth mechanism. Controlled doping, a necessary issue in order to realize advanced devices, is an unsolved problem and an extremely difficult task if using such a growth mechanism. We use an alternative route for modifying either the electrical, optical or magnetic properties of semiconductor nanowires: low energy ion implantation [1]. However, one cannot simply adapt bulk implantation parameters when the ion range is comparable to the size of the nanostructures. Therefore, we developed a new simulation tool in order to account for this. I will present the program iradina [2], as well as several recent studies on the modification of semiconductor nanowires by ion beam doping [3-7].
[1] C. Ronning, et al., Materials Science and Engineering R 70, 30 (2010)
[2] C. Borschel, C. Ronning, Nuclear Instruments & Methods B 269, 2133 (2011)
[3] S. Kumar, et al., Nano Letters 13, 5079 (2013)
[4] J. Segura-Ruiz, et al., Nano Letters 11, 5322 (2011)
[5] A. Colli, et al., Nano Letters 8, 2188 (2008)
[6] S. Geburt, et al., Nano Letters 14, 4523 (2014)
[7] A. Johannes, et al., Nano Letters 15, 3800 (2015)
NM05.04: Plasmas in Liquids—Atmospheric and High Pressures
Session Chairs
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 313
1:30 PM - *NM05.04.01
Conditions to Form Alloy Nanostructures by Nanosecond-Pulsed Discharges in Liquid Nitrogen
Hiba Kabbara 1 , Alexandre Nomine 1 , Jaafar Ghanbaja 1 , Cédric Noël 1 , Thierry Belmonte 1
1 , IJL - CNRS - Universite de Lorraine, Nancy France
Show AbstractIn 2008, Alayoglu et al. (1) published a seminal paper where they showed that PtRu alloy nanostructures have a significantly different catalytic activity from that of a mixture of monometallic Pt and Ru nanostructures under identical loadings and conditions. Growing such alloy structures by a simple, low-cost and fast process would be highly competitive. Discharges in liquids offer a simple way to synthesize nanoparticles at high rate and low cost. When spark discharges are ignited in a dielectric liquid, a strong heating of the electrode material occurs, producing a metallic vapour from which nanostructures grow by condensation.
However, forming alloy nanostructures by discharges in liquid nitrogen that erode alloy electrodes is not straightforward. Indeed, several difficulties can arise and limit the formation of alloy nanostructures. When metallic elements forming the alloy exhibit very similar properties, like in the Cu-Ag system (similar melting points, ionization energy, weak affinity towards oxygen), then the formation of alloy structures is possible. On the other hand, when both elements have very different properties, as in the Cu-Zn system, the formation of alloy nanostructures is impossible and post-treatments, by laser for instance, are then needed to associate both elements by fast heating and quenching.
In this presentation, we will compare the behaviours of Cu28Ag72 and Cu63Zn37 alloy electrodes when submitted to discharges in liquid nitrogen. By resorting to advanced TEM characterizations and by coupling them with time-resolved optical emission spectroscopy, we will give an in-depth description of processes at stake in each case, explaining the origin of the difficulties encountered to form alloy nanostructures.
(1) S. Alayoglu, A. U. Nikelar, M. Mavrikakis, B. Eichhorn, Nature Materials (2008), 7, 333–338
2:00 PM - NM05.04.02
Atmospheric Plasma Deposition of Organic-Inorganic Hybrid Thin Films with Engineered Optical and Mechanical Properties
Michael Hovish 1 , Reinhold Dauskardt 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractHybrid thin films have augmented functionality due to coupling of multiple material properties. We describe the synthesis of a hybrid thin film containing an inorganic TiOx network interpenetrating an organic carbon-rich network. Titanium dioxide has a high refractive index and hardness, while amorphous carbon can be toughened through cross-linking. Therefore, a range of mechanical and optical properties can be derived from an admixture in the form of a plasma polymer. The use of an atmospheric plasma nitrogen discharge facilitated high growth rates of these transparent thin films in open air. Spectroscopic ellipsometry (SE), spectral reflectivity (SR), high-resolution x-ray photo-electron spectroscopy (XPS), and nano-indentation were performed to elucidate the connection between processing and material properties. We show that varying the concentration of the inorganic phase within the organic matrix resulted in excellent control over optical and mechanical properties. An extensive range in refractive index is observed for the hybrid material, n varying between 1.85 – 2.25. Organic-inorganic hybrid thin films are deposited with high visible transmission, low visible reflectance, and moderate near-infrared reflectance. By balancing the numerous reactions between film precursors and the energetic backdrop in an atmospheric plasma, we can enable new deposition routes for high refractive index hybrid thin films.
2:15 PM - NM05.04.03
Combinatorial Synthesis of Nanoparticle Libraries by Co-Sputtering into Ionic Liquids
Alfred Ludwig 1 , Gesa Zahn 1 , Christina Kuchshaus 1 , Christoph Somsen 1
1 , Ruhr-University Bochum, Bochum Germany
Show AbstractMultinary metal nanoparticles are of interest for their application as catalysts, for example in fuel cells. High-throughput and combinatorial methods are suitable to identify promising materials. Generally, combinatorial magnetron sputtering offers the possibility to fabricate a large quantity of well-defined multinary material combinations during one deposition, resulting in a material library. By using non-volatile ionic liquids as substrate, the combinatorial co-sputtering process allows syntheses of unary as well as binary and ternary alloy nanoparticles. For this purpose, we use a cavity array Si wafer which cavities are filled with the ionic liquid. In the sputter system, the sputter targets consisting of pure elements are tilted to obtain a concentration gradient that results in the synthesis of nanoparticles with different compositions. With this synthesis procedure, the fabrication of various material combinations is possible. In a first approach, we investigated several nanoparticle systems (Cu-Au, Ni-Co, Ni-Mn, …) by using transmission electron microscopy (TEM). Non-agglomerated, crystalline nanoparticles with diameters < 10 nm were observed.
2:30 PM - NM05.04.04
Nanopatterning of Chitosan/Bacterial Nanocellulose Hydrogels by Liquid Plasma and Directed Plasma Nanosynthesis
Camilo Jaramillo 1 , Akshath Shetty 1 , Ana Civantos 1 , Sandra Liliana Arias 1 , Joshua Craig Devorkin 1 , Jean Paul Allain 1 , Shuquan Chang 2
1 , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 , Nanjing University of Aeronautics and Astronautics, Nanjing China
Show AbstractLow-temperature and thermalized plasma-assisted techniques are interesting due to their broad capabilities to enhance or induce new characteristics to processing materials. By means of plasma treatment, processes such as etching, cleaning, deposition or functionalization (e.g. nanopatterning) can be performed on surfaces1,2. Directed plasma nanosynthesis (DPNS), where the extraction and recombination of particle species with specific characteristics is used to produce nanostructured materials, has been established as a versatile materials modification approach on a wide class of materials. Given that conventionally plasma treatment has been used to induce changes in the surface morphology and to introduce metallic nanoparticles (NP) on the surface of the polymers3, the current study examines differences between thermalized and non-thermal plasmas. In particular, high-fidelity control of surface nanotopography, NP synthesis and surface chemistry changes in natural hydrogels are studied.
DPNS in thermal and non-thermal states is used to synthesize Au and Ag NPs on natural hydrogels including bacterial nanocellulose (BNC) and chitosan films. These natural biopolymers with properties such as biocompatibility, biodegradability and low toxicity, have been previously used for drug delivery systems, artificial tissue and biosensor applications4. Similarly, gold and silver NPs have been used to modify the antimicrobial and cell adhesion properties of surfaces5.
Au/Ag modified BNC and Chitosan films were produced in two different domains: low-energy atmospheric-pressure plasma and higher-energy high-vacuum plasma. The presence of plasma-induced nanotopography was evaluated. SEM and EDS were used to examine the morphology and composition of the modified films, respectively. In addition, in-situ surface functionalization of chemistry correlated to surface topography during irradiation was measured with environmental XPS. Both environments produced different structures on the surface of the films. The stability of these structures in aqueous environments and the antimicrobial properties of the Au/Ag modified BNC and Chitosan films was evaluated. A significant transformation of BNC hydrogels is found changing to a self-organized pillar structure without loss of hydrophilicity, while Chitosan hydrogels are converted from hydrophobic to hydrophilic state including a change in topography.
[1] R. Foest, E. Kindel, A. Ohl, M. Stieber, K.-D. Weltmann, Plasma Phys. Control. Fusion 47 (2005) B525–B536.
[2] O. El-Atwani, S. Gonderman, A. Demasi, A. Suslova, J. Fowler, M. El-Atwani, K. Ludwig, J. Paul Allain, J. Appl. Phys. 113 (2013) 124305.
[3] N. Slepičková Kasálková, S. Stýblová, P. Slepička, S. Rimpelová, V. Švorčík, Int. J. Nanotechnol. 14 (2017) 120.
[4] J. Kim, Z. Cai, H.S. Lee, G.S. Choi, D.H. Lee, C. Jo, J. Polym. Res. 18 (2011) 739–744.
[5] X. Deng, A.Y. Nikiforov, T. Coenye, P. Cools, G. Aziz, R. Morent, N. De Geyter, C. Leys, Sci. Rep. 5 (2015) 10138.
2:45 PM - NM05.04.05
Plasmachemical Double-Click Thiol-Ene Reactions for Wet Electrical Barrier
Jas Pal Badyal 1
1 , University of Durham, Durham United Kingdom
Show AbstractThe continual drive towards smaller portable electronics with greater functionality (e.g. smartphones and wearable devices) is leading to more stringent demands for device performance (e.g. operation during immersion in water or protection against accidental spillage). Hence, there exists a strong demand for high electrical barrier coatings which block water ingress in order to prevent device failure through corrosion, degradation, or electrical short circuiting. Polymeric layers are at the forefront of such protective coatings due to their high electrical insulation and low permeation properties. Further enhancement of electrical barrier properties can be achieved through crosslinking. Therefore, in principle, a combination of crosslinking and multilayering should lead to further improvement in electrical barrier performance. This is achieved using plasmachemical thiol-ene click reactions. A structure-behaviour relationship study shows that the alkene-thiol precursor (allyl mercaptan) undergoes formation of a thiol-ene self-crosslinked nanolayer during plasma deposition in tandem with interfacial crosslinking to an alkene bond containing polymer base layer. The attained synergistic multilayer structure displays high wet electrical barrier performance during immersion in water [1].
[1] ACS Applied Materials and Interfaces 8 (2016), 21832–21838.
3:30 PM - NM05.04.06
Tandem Laser Ablation Synthesis in Solution-Galvanic Replacement Reaction as a Facile and Surfactant-Free Route for the Synthesis of Tailored Nanoalloys as Superior Oxygen Reduction Reaction Electrocatalysts
Sheng Hu 1 , Dibyendu Mukherjee 1
1 , University of Tennessee, Knoxville, Knoxville, Tennessee, United States
Show AbstractEfficient yet, low-cost electrocatalysts are indispensable for electrochemical oxygen reduction reactions (ORR) in the field of proton exchange membrane fuel cell (PEMFC). In this work, we have synthesized ternary nanoalloys (NAs) of Pt with transition metals (Co, Cu, Ni, Ti, Ru, Mn) as oxygen reduction reaction (ORR) electrocatalysts using our recently developed laser ablation synthesis in solution-galvanic replacement reaction (LASiS-GRR) technique as a facile and green nanomanufacturing route. The specific choice of the elemental compositions is driven by the respective target metal/metal salt redox potential gradients as well as the target metal and/or, metal oxide solubility in the desired acid. The extreme out-of-equilibrium thermodynamic conditions for the LASiS-GRR process enables directed control on the sizes, elemental compositions and distributions of the ternary NAs through systematic tuning of initial metal salt concentrations, pH and ablation time. Specifically, the PtCuCo NAs synthesized with an elemental composition of 72:12:16 (Pt:Co:Cu) indicates the best ORR catalytic activities. The NAs are largely determined to be shell-core structures with the shell comprising mostly Pt and some minor Cu, along with a uniformly alloyed PtCuCo core. Mass and specific activities for ORR performance of the NAs indicate a 4 and 6.5-fold improvements respectively over the corresponding activities of commercial Pt/C. We attribute these activities to 1) our surfactant/ligand-free green synthesis technique that prevents catalytic site degradations; and 2) minor alloying of the second transition metal Cu that shifts back the Pt d-band center to optimally position it between that for Pt and the PtCo binary NAs, thereby tuning their binding affinities for both oxygen and oxygenated species. Finally, this work establishes the versatility of the LASiS-GRR technique through the synthesis of other ternary NAs (PtRuNi, PtCoMn, PtNiTi) that also exhibit reasonably good ORR activities.
3:45 PM - NM05.04.07
Simultaneous Insulation and Modification of Quartz Tuning Fork Surface by Single Step Plasma Polymerization Technique with Amine Rich Precursors
Pelin Komurcu 1 , Gizem Kaleli Can 2 , Ferda Ozguzar 2 , Gözde Kabay 2 , Mehmet Mutlu 2 3
1 Plasma Aided Biomedical Research Group (PABMED) Micro and Nanotechnology Department, Graduate School of Science and Technology, TOBB University of Economics and Technology, ANKARA Turkey, 2 Plasma Aided Biomedical Research Group (PABMED) Biomedical Engineering Department, Graduate School of Science and Technology, TOBB University of Economics and Technology, ANKARA Turkey, 3 Plasma Aided Biomedical Research Group (PABMED) Biomedical Engineering Department, TOBB University of Economics and Technology, ANKARA Turkey
Show AbstractQuartz tuning fork (QTF) has started to replace quartz crystal microbalance (QCM) as a mass sensitive transducer due to its reproducibility, sensitivity, cost and other properties (i.e. quality factor, response time). The main problem of QTF as a transducer to be used in a biosensor is its inadequate performance in aqueous medium. Plasma polymerization (PlzP) process is a common method in order to modify the surfaces. In this study, amine containing polymer thin films of amylamine or 1,2-diaminocyclohexane or n-heptylamine were prepared by low frequency and radio frequency plasma polymerization processes. This single step insulates and functionalizes the QTF surface with amino groups, simultaneously. Experiments were conducted at different discharge powers (30 W, 60 W, 75 W and 90 W) and deposition periods (1 min, 3 min, 5 min and 10 min). The resistivity of QTF samples were increased from 0.01 MΩ up to 4.28 MΩ. The film stability was investigated with frequency measurements and aging tests. An untreated QTF shows a frequency of 32.768 kHz in vacuum where as in atmospheric and PlzP treated conditions this frequency drops due to accumulation of a thin film (<100 nm) on the QTF prongs. Aging test were performed in both aqueous and atmospheric conditions and examined with contact angle measurements. It has been observed that some of the samples keep hydrophilic property for 30 days in these measurements. The others were degraded and turned into slightly hydrophilic , due to chemical reaction of functional groups with oxygen in atmosphere. These data were cross-checked with Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR). Further investigation carried out with Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Photoelectron Spectroscopy (XPS). These promising results lead us to develop a QTF based mass sensitive immunosensor.
4:00 PM - NM05.04.08
Formation of MoO3 and WO3 Nanoscrolls from MoS2 and WS2 by Atmospheric Air Plasma
Ximo Chu 1 , Duo Li 1 , Alexander Green 1 , Qing Hua Wang 1
1 , Arizona State University, Tempe, Arizona, United States
Show AbstractNanostructured transition metal oxides (TMOs) have interesting electrochemical and physical properties that make them useful in a variety of applications such as lithium-ion batteries, solar cells, gas sensors, and thermoelectrics. Nanostructured forms of TMOs have improved performance in these applications due to a higher surface-to-volume ratio, and in particular nanoscroll geometries provide more accessibility for chemical interactions throughout their internal surfaces. Here, we report the synthesis of MoO3 and WO3 nanoscrolls directly from atomically thin layers of two-dimensional MoS2 and WS2 by atmospheric air plasma treatment. The morphology of the nanoscrolls was characterized by atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) measurements confirm the formation of oxides. We propose a rolling mechanism that depends on reactive species that form from a mixture of nitrogen, oxygen, and water vapor acting on the initial material, as well as on stresses in the material upon oxidation. This simple method for forming TMO nanoscrolls using atmospheric air plasma suggests new routes for plasma-based nanostructure synthesis for potential electrochemical applications.
4:15 PM - NM05.04.09
Laser Induced Incandescence Method for Nanoparticle Characterization in High-Pressure Arc Plasma
Shurik Yatom 1 , Junhwi Bak 2 , Alexander Khrabryi 1 , Y Raitses 1
1 Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey, United States, 2 Department of Aeronautics and Astronautics, The University of Tokyo, Tokyo Japan
Show AbstractFirst laser-induced incandescence measurements were conducted in the high-pressure plasma of the carbon arc discharge. The purpose of the diagnostics is to study the synthesis of carbon nanostructures, via characterizetion of their size, as a fuction of distance from the arc axis. The results revealed two spatial regions occupied by dominant populations of carbon particles with different sizes. Close to the axis of the arc, large micron size particles dominate the incandescence signal, while in the arc periphery, the incandescence is dominated by ~20 nm particles. Using a heat transfer model between the gas, arc plasma and the particles, it is shown that such a drastic difference in the particle sizes can be explained by evaporation of the micron-scale particles, from the consumed anode, which move across the arc plasma towards the arc periphery. It is also hypothesized that mass evaporated from the micro particles contributes to the carbon feedstock for the formation of nanostructures.
Acknowledgement
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
References
S Yatom, J Bak, A Khrabryi, Y Raitses, Carbon 117, 154-162
4:30 PM - NM05.04.10
The Effect of Precursor Droplet Size on the Gas-Phase Synthesis of Graphene in Plasmas
Philip Digiacomo 1 , Pichaya Lertvilai 1 , Tom Donnelly 1 , Albert Dato 1
1 , Harvey Mudd College, Claremont, California, United States
Show AbstractGraphene can be synthesized through the substrate-free gas-phase synthesis method, which is a single-step process that involves delivering an aerosol consisting of argon gas and liquid ethanol droplets directly into an atmospheric-pressure microwave-generated argon plasma. The technique utilizes a pneumatic nebulizer to generate aerosols that result in the production of clean and highly ordered graphene. However, the size of the ethanol droplets produced by the nebulizer has not been experimentally determined, and other methods of atomizing ethanol have not been investigated. Here, we will discuss the dependence of graphene synthesis on the size of aerosol particles that are delivered to the plasma. Mie scattering experiments that determine particle size distributions of two different aerosol production methods—pneumatic nebulizer and ultrasonic atomizer—indicate that aerosol particle size has a significant effect on the production of graphene in plasmas. Our results show the importance of droplet evaporation in the graphene synthesis process, and demonstrate a means of controlling the types of carbon nanomaterials produced in atmospheric pressure plasmas.
Symposium Organizers
David Horwat, Institut Jean Lamour-University de Lorraine
R. Mark Bradley, Colorado State University
Ulf Helmersson, Linköping Universitet
François Reniers, Université Libre de Bruxelles
NM05.05: Nanoparticles, Nanocrystals and Nanostructures I
Session Chairs
Thierry Belmonte
Ulf Helmersson
Wednesday AM, November 29, 2017
Hynes, Level 3, Room 313
8:00 AM - NM05.05.01
Synthesis and Optical Properties of Plasmonic-Metal Nanostructures by Pulsed Laser Deposition
Matteo Ghidelli 1 , Luca Mascaretti 1 , Beatrice Bricchi 1 , Andrea Zapelli 1 , Valeria Russo 1 , Carlo Casari 1 , Andrea Li Bassi 1
1 , Politecnico di Milano, Milan Italy
Show AbstractMetallic nanoparticles (NPs) have attracted the attention of the scientific community because of their interesting optical properties [1]. The size confinement of metallic NPs at the nanometer scale enables the activation of the localized surface plasmon resonance (LSPR), resulting in a collective electron oscillation triggered by the selected light frequencies [1]. Engineering NPs enables to tune specific LSPR wavelengths as requested by several applications in the fields of optoelectronics, nanomedicine and substrate development for Surface Enhanced Raman Scattering (SERS). Moreover, plasmonic NPs can be integrated in wide band gap semiconductors (TiO2, ZnO) increasing the light harvesting beyond the ultraviolet region with clear applications e.g. in the field of thin film photovoltaics and solar fuel production with hydrogen generation [2].
Metallic NPs are often produced by liquid phase techniques involving nucleation and growth phenomena [1]. While this approach enables to accurately control the size and shape of NPs, the main drawback is represented by the use of solvents, which can affect the NP properties as well as induce damaging especially for delicate applications involving polymeric substrates. On the other hand, vapor phase techniques, including sputtering and evaporation, often require heating steps, while the control of NPs size distribution is more complicated [2].
Here, vapor phase Pulsed Laser Deposition (PLD) technique is used to produce plasmonic Au NPs and percolating Au nanostructures on surfaces [3]. A wide range of PLD process parameters – including background gas pressure, the number of laser shots and post-deposition annealing treatments – has been studied to control the growth of Au NPs and layers, enabling to tune the surface plasmon characteristics [3]. A morphological characterization involving Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) has been carried out and related with the optical behavior. We show that: (i) the size distribution and the morphology of the as deposited Au NPs depend on the number of shots and the background gas pressure and we obtained up to 16 nm-diameter Au NPs without substrate heating or annealing treatments; (ii) the optical behavior is strongly affected by the average size and distance between NPs and by the length of percolated Au domains; (iii) in-plume nucleation phenomena has been reported at high (1000 Pa) background pressures, enabling independent control of NP size and coverage, contrary to NP growth by diffusion and surface aggregation. Finally, the mechanisms of film growth as a function of PLD parameters are explored. These results pave the way to the deposition of Au NPs and nanostructured films with tuned properties and their integration in wide band gap semiconductors.
[1] H.A. Atwater & A. Polman, Nature Mater. 9, 205-203 (2000).
[2] S. Mubeen et al. Nano let. 11, 5548-5552 (2011).
[3] M. Ghidelli et al. submitted to Materials & Design (2017).
8:15 AM - NM05.05.02
Effect of Rapid Thermal Annealing on Crystallization and Stress Relaxation of SiGe Nanoparticles Deposited by ICP PECVD
Florent Ravaux 1 , Irfan Saadat 1 , Mustapha Jouiad 1
1 , Masdar Institute of Science and Technology, Abu Dhabi United Arab Emirates
Show AbstractSi-Ge compound has been successfully implemented in complementary metal–oxide–semiconductor transistor technology thanks to the successful development of hetero epitaxial layer growth by metal-organic chemical vapor deposition and molecular beam epitaxy techniques. These techniques can provide defect free Si-Ge layer on silicon substrates which gave rise to the strain engineering era, significantly boosting MOSFET performances.
SiGe compound can also be used in various applications with respect to its morphology. Indeed, SiGe nanoparticles embedded in SiO2 can be used in electronic memories and optoelectronic devices. It has also been demonstrated that porous poly-SiGe layers are also desirable for applications in light emitting materials. Finally, SiGe porous layer can also be used in thermoelectric applications. Indeed, thermal conductivity and Seebeck effect can be tuned as a function of pore diameter of the porous SiGe layers.
In this study, we demonstrate viability of direct fabrication utilizing a single (deposition/anneal) process for polycrystalline Silicon Germanium sub-micro particles. The process combines plasma chemical vapor deposition enhanced with inductively coupled radio frequency plasma at intermediate pressure and high temperature for the deposition and Rapid Thermal Annealing as a final step to tune the morphology of the layer.
The deposition process utilizes high plasma density at low kinetic ion energy providing relatively high deposition rate, favorable for industrial fabrication requirements. Our characterization was performed at two points in the process, post-deposition and post-anneal. Raman spectroscopy and x-ray diffraction were combined to determine the value of stoichiometry x and hence the nature of the obtained compound. Post-anneal the samples were analyzed by atomic force microscopy, scanning and transmission electron microscopy to investigate the crystallization, growth kinetics and the strain relaxation of the particles.
Our findings show that the optimized coarsening of the crystals occurred after annealing at 600°C for 30 minutes resulted in internal strain minimization while the composition stoichiometry is kept constant. In addition, the presence of well-defined geometrical facets observed on the surface of SiGe particles, as revealed by atomic force microscopy analyses, suggests that the SiGe particles seem to grow along a preferred crystallographic orientation.
8:30 AM - NM05.05.03
Hybridised Silicon Nanospheres by PECVD for Enhanced Wavelength Selection
Jonathon Mitchell 1
1 , National Institute of Advanced Industrial Science and Technology, Koriyama Japan
Show AbstractWe present the first fabrication of hybridised silicon nanospheres by simplified plasma-enhanced chemical vapour deposition, without seed particle injection or microwave plasma. Many nanospheres can be amorphous or crystalline in nature, however, the in situ hydride inception of these particles offers a unique processing advantage over other methods of fabrication. This new technique reduces the necessity of colloidal suspension or centrifugation steps in order to incorporate nanospheres directly into dielectric materials for light trapping or wavelength selection.
The degree of uniformity for nanospheres can be incorporated into the dielectric layer during deposition, or simply grown onto a suitable substrate for colloidal extraction. In the hybridised condition, we have observed incorporated nanospheres integrated into materials like a-Si:H, SiN or SiO, enhancing light trapping without compromising conductivity or passivation of the underlying crystalline silicon surface.
Suspension in poly-vinyl alcohol or ethyl acetate offers liquid phase analysis prior to evaporation, and permits further functionlisation of the nanospheres, including doping to n-type or p-type. The zeta potential of the spheres was measured from their electrophoretic mobility.
As the physiochemical properties of nanoparticles depend on their size and shape, isolation within a suitable matrix permits single-particle experimentation, overcoming averaging effects. Given nanospheres tend to have a higher specific surface area, the particle morphology was analysed. Plasmonic nanospectroscopy, FTIR and Raman, provided a comprehensive study of hydride formation with size and shape dependencies. Observed hysteresis exhibited wider profiles than the bulk dielectric. In this, coherent phase transitions, as a result of hydride formation either at the surface of the nanospheres or within the bulk, indicated that hydride decomposition occurs incoherently at present. Confocal microscopy data from different optical cross sections showed that the H-Si distribution was homogeneous in microspheres with no evidence of surface or bulk aggregation being present.
Images obtained from Scanning Electron Microscopy (SEM) were investigated using an image analysis software package to obtain the particle size distribution of the microspheres and nanospheres. The interference of light scattering from spheres in the absorbance spectra was analysed by UV-VIS-NIR. These nanospheres have a density of 1.95 g/cm3 and 2.25 g/cm3 and an index of refraction between 2.4 and 4.7 at 625 nm (25°C).
Currently, the manifestation of multisublattice ordering and the observance of exchange bias effects are being focused upon. We aim to induce hyperpolarization spin-states through adherent-hydrogen induced polarisation. Recent studies in our laboratory have shown that in low-dimension dielectric, the hybridised nanospheres may exhibit photocharge inheritance of spin-states correlated by nuclear magnetic resonance measurements.
8:45 AM - *NM05.05.04
Nonthermal Plasma Synthesis of Semiconductor Nanocrystals and Quantum Dots for Electronic and Energy Applications
Uwe Kortshagen 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractNonthermal plasma synthesis of nanocrystals relies on the plasma’s pronounced nonequilibrium character. Molecular precursors are dissociated by electron impact reactions and the resulting molecular fragments and radicals, many of them charged, nucleate to form clusters and nanocrystals. Energetic surface reactions can heat these initial clusters to temperatures that exceed the gas temperature by hundreds of Kelvin. This enables plasmas to form crystalline nanoparticles of strongly covalently bound materials, which require high temperatures for crystallization. This presentation briefly discusses the physics of the plasma synthesis process.
Several years ago, our group showed that nonthermal plasmas are capable of producing high quality silicon crystals. With the proper surface functionalization such silicon nanocrystals exhibit high-efficiency photoluminescence, different from bulk silicon material. The high photoluminescense quantum yields are achieved by careful surface functionalization through grafting alkene ligands to the nanocrystal surfaces. Solar luminescent concentration is a potential application for these highly luminescent nanocrystals (Nature Photonics 2017).
The capability of nonthermal plasmas to produce substitutionally doped nanocrystal materials has also attracted attention, as substitutional doping had presented a significant challenge both for liquid and gas phase synthesis due to effects such as self-purification. We discuss the substitutional doping of silicon nanocrystals with boron and phosphorous using a nonthermal plasma technique. The ability of plasmas to produce doped nanocrystals has recently enabled new insights into the electronic transport in nanocrystal films, leading to the development of a new theory for the insulator-to-metal transition in directly connected nanocrystal networks (Nature Materials 2016).
The author's work is supported by the University of Minnesota MRSEC under Award Number DMR-1420013, the DOE Plasma Science Center for Control of Plasma Kinetics, the DOE Energy Frontier Research Center for Advanced Solar Photophysics, and by the Army Office of Research under MURI Grant W911NF-12-1-0407.
9:15 AM - NM05.05.05
High Throughput, Room Temperature Synthesis of Cluster Assembled Nanostructured Nanocrystalline Silicon Films
Giorgio Nava 1 , Francesco Fumagalli 1 , Salvatore Gambino 2 , Giorgio Dell'Erba 1 , Gabriella Cavallo 3 , Giancarlo Terraneo 3 , Giorgio Divitini 4 , Cate Ducati 4 , Mario Caironi 1 , Adriano Cola 2 , Fabio Di Fonzo 1
1 , IIT, Milano Italy, 2 , Università del Salento, Lecce Italy, 3 , Politecnico di Milano, Milan Italy, 4 , University of Cambridge, Cambridge United Kingdom
Show AbstractSince its discovery in 1968, nanocrystalline silicon, a biphasic material comprising of an amorphous hosting matrix with embedded silicon nanocrystals, attracted considerable attention due to the superior stability and carrier mobility with respect to its amorphous counterpart in combination with a comparable high absorption coefficient. Additional flexibility arises from the tunable optical, electronic and light emitting properties of the nanocomposite, depending on the size and amount of the crystallites inclusions. Standard synthesis routes suffer however from high processing temperatures, low yield and lack of morphology control, hindering a technological breakthrough in fields such as thin films transistors and photovoltaics. Despite a high number of fundamental investigations on nanocrystalline materials properties, a comparatively smaller attention was dedicated to the means of their application. In this work we demonstrated the possibility of transferring fundamental findings into cluster assembled semiconductor-based devices by means of a deposition techniques capable of (i) directly depositing nanocrystals as a dense thin film with high throughput on appropriately large areas, (ii) controlling nanocrystals fundamental compositional characteristics like crystalline fraction and nanocrystals grain size, (iii) depositing nanocrystals on a wide variety of substrates, including thermolabile polymeric materials.
We present a large area (100 cm2), ultra-high yield (up to 1 μm min-1 or 300 mg h-1), plasma-based deposition technique (Nanoparticles Jet Deposition) of nanocrystalline silicon cluster-assembled thin films compatible with thermolabile substrates. The process is based on the segmentation of the gas phase material synthesis in two steps: (i) nanoclusters synthesis and growth control in a nonthermal dusty plasma environment, allowing in-flight, low temperature crystallization; (ii) nanoparticles-assembled films ballistic growth via super sonic jet acceleration. Nanocomposite materials showing densities up to 50% of bulk silicon can be directly synthetized with crystalline fractions ranging from 0 to 72% and the nanocrystalline inclusion sizes can be tuned in the range from 2 to 5.5 nm with subnanometers size distributions Time of flight spectroscopy is employed to investigate nanoparticles-assembled films charge carriers transport mechanisms in anomalous dispersive regime. Mobility up to 2 Å~ 10-5 cm V-1 s-1 was observed, reaching the highest reported mobility for a silicon nanoparticles-assembled film deposited at low-temperature. An ultra-high yield synthesis route producing high quality silicon-based thin films at polymer-compatible temperatures represents the first step for a powerful integration of the well-known inorganic semiconductors technology with emerging trends in freestanding nanocrystals synthesis.
9:30 AM - NM05.05.06
Birth of Silicon Nanowires Covered with Protective Silicon Oxide Blanket
Krishna Nama Manjunatha 1 , Shashi Paul 1
1 , De Montfort University, Leicester United Kingdom
Show AbstractIn recent years, there has been a significant interest in one-dimensional nanostructures that include nanowires (NWs) and nanotubes. Nanowire applications include solar cells, field effect transistors, sensors and charge storage memory devices [1,2]. One of the critical aspects that facilitates the use of NWs in functional devices and/or useful structures is the adoption of coating strategies. This provides additional benefits such as minimised gate leakage in transistors, reduced shunt paths in solar cells, anti-reflection coating and surface passivation of nanowires to minimise surface states while enhancing electrical and optical properties. To realise the coating of NWs; fabrication process should be scalable, provide conformal coating across the complete cross-section of a nanowire, low-temperature process and do not cause damage to NWs. Different fabrication processes have been proposed and they also have certain disadvantages. These include the requirement of high temperatures, non- deterministic sticking coefficient, non-conformal coating due to shadowing of nanowires, lattice mismatch and damage caused to the nanowires and the influence of the fabrication process to other layers within the device.
This work reports on the growth of SiNWs coated with silicon oxide (SiOx ) shell by plasma-assisted-vapor-liquid-solid method. This has been achieved without the use of additional fabrication processes due to the simultaneous growth of a silicon (Si) core and SiOx shell from a Tin oxide catalyst obtained by decomposition of organic and inorganic compounds of Tin. This process facilitates the growth of pristine SiNWs that are not influenced by atomic species in the plasma due to simultaneous precipitation of the shell over Si core. Growth discussed here will lead to the possibility to control dimensions and morphology of Si-SiOx NWs. To the best of the authors’ knowledge, this is the first report on the growth of core-shell SiNWs achieved by decomposition of organic and inorganic compounds. This growth process allows a better conformal coating irrespective of nanowire morphology. Compositional studies and morphology of core-shell SiNWs are carried out using Scanning Transmission Electron microscope coupled with Energy Dispersive X-ray spectroscopy. Although it is not done in this work, if optimised, similar growth process can be applied to grow SiNWs passivated with nitride (-N) or hydride (-H) atoms in a single in situ fabrication growth process which eliminates additional deposition process used for passivation of SiNWs.
References
[1] N. Gabrielyan, K. Saranti, K. N. Manjunatha and S. Paul, "Growth of low temperature silicon nano-structures for
electronic and electrical energy generation applications," Nanoscale Research Letters, vol. 8, pp. 1-7, 2013.
[2] K. N. Manjunatha, and S. Paul. "In-situ catalyst mediated growth and self-doped silicon nanowires for use in nanowire solar cells." Vacuum.,vol 139, pp.178-184., 2017.
9:45 AM - NM05.05.07
Controlled Synthesis of Highly Specific Silicon Nanoparticles with a Low-Pressure Microwave Plasma Reactor on the Pilot-Plant Scale
Frederik Kunze 1 , Stefan Kuns 1 2 , Tim Huelser 1 , Mathias Spree 1 , Hartmut Wiggers 2 , Sophie Schnurre 1
1 , Institute of Energy and Environmental Technology e. V. (IUTA), Duisburg Germany, 2 , Institute for Combustion and Gas Dynamics – Reactive Fluids and CENIDE, University of Duisburg-Essen, Duisburg Germany
Show AbstractNanoparticles have created a high interest by virtue of their size-dependent features such as changing mechanical, electrical, optical, and magnetic properties, enabling application fields that utilize these features. To manufacture materials with specific, size-dependent properties, several manufacturing methods have been developed.
Besides many wet-chemical approaches, gas phase synthesis is one of them and is considered as highly suitable method to produce specific nanoparticles in large amounts. Especially plasma reactors have shown that they fulfill the requirements needed for specific applications that cannot be assured by other type of gas phase reactors. The plasma synthesis provides on the one hand the possibility to produce many different material systems and on the other hand an excellent control of the particle size and morphology, often due to steep temperature-time profiles. In addition, particle charging in the plasma plays a key role. These characteristics of plasma reactors lead to unique properties of nanoparticles from plasma reactors such as spherical shape, low degree of agglomeration, and comparably narrow size distribution.
In this work, silicon nanoparticles made from gaseous monosilane are used to investigate how the particle properties can be modified by adjusting specific process conditions such as pressure, precursor concentration, mass flow and microwave power. The experiments are carried out with a low-pressure microwave plasma reactor at pilot scale. This reactor uses microwaves with a frequency of 915 MHz and provides a power of up to 50 kW. In order to characterize the growth process of the particles within the plasma reactor, samples of particles were extracted directly from the gas phase at different distances from the plasma utilizing high-speed thermophoretic sampling.
It will be shown that this reactor enables the formation of highly crystalline and either soft-agglomerated or hard-agglomerated silicon nanoparticles. The systematic investigation of the process conditions revealed that the particle size and morphology can be independently controlled by a selective adjustment of the process conditions. We identified that the initial particle growth is mostly affected by the flow velocity within the nozzle injecting silane, while the final mean particle size is basically dependent on the overall residence time. Moreover, increasing formation of aggregates is observed with increasing silane concentration.
The long-term stability of the process has been proven by continuous particle synthesis for several hours at high production rate of up to 200 g/h.
10:45 AM - NM05.05.09
Formation of Lattice-Matched GeSiSn/Ge Quantum Well Structure by Sputter Epitaxy Method
Takahiro Tsukamoto 1 , Kazuaki Haneda 1 , Hiroto Iwamori 1 , Nobumitsu Hirose 2 , Akifumi Kasamatsu 2 , Toshiaki Matsui 2 , Yoshiyuki Suda 1
1 , Tokyo University of A&T, Tokyo Japan, 2 , NICT, Tokyo Japan
Show AbstractGeSiSn is a promising material for future electronic devices, because the band-gap and lattice-constant can be controlled separately and group IV lattice-matched heterojunction devices can be achieved. However, at a high Sn content, Sn segregation can occur during the growth due to the low solubility of Sn in Si and Ge and this can degrade the device performance. The development of the growth technique still remains a challenge. Sputtering is a widely used conventional method of forming thin films at the wafer level and semiconductor thin films can be formed in epitaxy by adjusting the sputtering conditions [1]. Previously, it is reported that high crystalline GeSn layers with high Sn content can be formed by sputtering and the high growth rate and the low-temperature growth can be effective in limiting the Sn surface segregation [2,3]. This technique can also be applied to the formation of GeSiSn layers. In this study, we have investigated the formation of lattice-matched GeSiSn/Ge quantum well structure by sputtering.
GeSiSn layers were formed on Ge (001) substrates by sputtering. A mixture of Ar and 5 vol% H2 combination gas was used as the sputter gas. The substrate temperature was maintained in the range from 548 to 623 K during the deposition. The lattice constant was characterized by X-ray diffraction two-dimensional reciprocal space map (XRD-2DRSM) and the GeSiSn layers lattice-matched with Ge were obtained by adjusting the deposition rates of Si, Ge, and Sn. The surface morphology of the fabricated GeSiSn layers was observed by an atomic force microscope (AFM).
GeSiSn layers were formed on Ge substrates by sputtering. The surface flatness depended on the growth temperature and Sn surface segregation was observed at above 623 K. The RMS value of the GeSiSn layer without Sn segregation was about 0.42 nm. The crystallinity of the GeSiSn layers depended on the Sn content and decreased with increasing the Sn content. The theoretical band offset of the fabricated GeSiSn/Ge heterojunction is about 0.2 eV in a conduction band. A GeSiSn/Ge quantum well was formed and was characterized by a transmission electron microscope (TEM). From the TEM observation, a highly crystalline GeSiSn/Ge hetero epitaxial layer was obtained. The interface between GeSiSn and Ge was sharp and a GeSiSn barrier layer with about 2 nm thickness was obtained in this study. Group IV lattice-matched quantum well structure can be achieved by sputtering and this technique can be applied to the formation of quantum effect devices.
Acknowledgements: This research and development work was supported by JSPS KAKENHI Grant Numbers 16K18076 and the MIC/SCOPE #165103005. This work was partly carried out in Advanced ICT Devices Lab in NICT.
References: [1] T. Tsukamoto et al., Thin Solid Films 529, 34-38, 2015. [2] T. Tsukamoto et al., J. Mater. Sci. 50, 4366-4370, 2015. [3] T. Tsukamoto et al., Appl. Phys. Lett. 106, 052103, 2015.
11:00 AM - *NM05.05.10
Pulsed-Plasma Production of Nanoparticles—Strengths, Weaknesses and Opportunities
Nils Brenning 1 2 , Sebastian Ekeroth 1 , Rickard Gunnarsson 1 , Robert Boyd 1 , Ulf Helmersson 1
1 Plasma and Coatings Physics Division, IFM-Material Physics, Linköping University, Linköping Sweden, 2 Department of Space and Plasma Physics, School of Electric Engineering, KTH Royal Institute of Technology, Stockholm Sweden
Show AbstractThe experimental progress, the opportunities, and the theoretical challenges are reported in a broad project, in which different types of nanoparticles (NPs) are produced in pulsed hollow cathode discharges. The key to the pulsed power technique is a NP growth environment built up of a sequence of partially overlapping high density plasma clouds, in which the sputtered growth material has a high degree of ionization. This technique opens the possibility of a very fast NP growth, combined with a very efficient conversion of the sputtered growth material to deposited NPs on a substrate. With these new opportunities, however, follow new challenges. In particular, electric fields and NP charging become important in all phases: the growth, the transport, and the final collection of NPs on substrates. Productivity is possible to optimize by seeding the discharge gas, argon, with trace oxygen which stimulates dimer formation which is the first step in nucleation. With optimized discharge conditions the major part of the available growth material can thereby become transformed to NPs in a time span of milliseconds. Size control in the range 10 nm to more than 500 nm is demonstrated by various alternative control parameters: pulse frequency, pulse amplitude, pulse length, discharge geometry, gas pressure, and gas flow speed. A size dispersion below 10 % is shown to be achievable. Transport and collection on the substrate are challenges for the reason that the NP motion can be dominated by Brownian motion, electric fields, magnetic fields, gas flow drag, or gravity, all depending on the NPs magnetization, size, and charge. The effects of these problems are minimized by integrating the production of the NPs with an assembly directly out of the plasma phase, a technique we call integrated pulsed plasmas production and assembly, IPPPA. Regarding theory and modeling, different approaches are used in a sequence of five stages: (I) the production and ionization of sputtered material ejected from the hollow cathode, (II) the nucleation and growth of NPs so small that they are on the average uncharged, (III) the continued growth of NPs, of sizes such that they are on the average negatively charged, (IV) the transport of such negatively charged NPs from the growth zone to the substrate vicinity, and (V) the final attachment of them to a substrate. In the case of magnetized NPs, this last step is associated with self-organization of the NPs into nanowires and/or nanotrusses, depending on the collection method.
11:30 AM - NM05.05.11
Experimentally Assessing Nucleation Theory at the Molecular Level
Matthew Gebbie 1 , Nick Melosh 1
1 , Stanford University, Stanford, California, United States
Show AbstractNucleation is a core scientific principle, describing the formation of new phases and materials. To date, classical nucleation theory has been widely used to understand the plasma-enhanced deposition of materials. However, recent work shows that classical theory is incorrect for many mesoscopic systems, like proteins and colloids, and classical theory should be even less applicable at the atomic level. Currently, the direct observation of putative atomic-scale proto-nuclei during the synthesis of materials, like diamond or silicon, remains impractical, making it difficult to conclusively establish nucleation mechanisms for many important materials. We surmounted this challenge by directly measuring the nucleation energetics of diamond during plasma-enhanced chemical vapor deposition using a series of diamond molecules as atomically-defined proto-nuclei. Our results show that the nucleation barrier and surface energies for diamond are more than two orders of magnitude smaller than currently estimated values, and critical nuclei are composed entirely of surface atoms. To explain these results, we propose that nucleation occurs through a non-classical, two-step ‘collapsed surface atom’ mechanism with distinct nucleation and crystallization barriers. This model predicts greatly reduced nucleation barriers compared to classical predictions, resolving long-standing questions surrounding the synthesis of several industrially important materials.
11:45 AM - NM05.05.12
Arc Synthesis of Boron Nitride Nanotubes
Y Raitses 1 , Yao-Wen Yeh 2 , Shurik Yatom 1 , Rachel Selinsky 4 , Bruce Koel 4 , Predrag Krstic 3
1 , Princeton Plasma Physics Laboratory, Princeton, New Jersey, United States, 2 Princeton Institute for Science and Technology of Materials , Princeton University, Princeton, New Jersey, United States, 4 Department of Chemical and Bio Engineering, Princeton University, New York City, New York, United States, 3 Institute for Advanced Computational Science, SUNY at Stony Brook, New York, New York, United States
Show AbstractWe present recent results on stable and reliable synthesis of boron nitride nanotubes (BNNTs) in volume by an anodic arc discharge at near atmospheric pressure of nitrogen. This arc was operated with the boron-rich anode and the cathode made from a refractory metal which has a melting temperature above the melting point of boron. Ex-situ characterization of synthesized BNNTs with electron microscopy and Raman spectroscopy revealed that independent of the cathode material, the tubes are primarily single and double walled. The results also show evidence of root-growth of BNNTs produced in the arc discharge.
This work was supported by U.S. Department of Energy, Office of Science, Basic Sciences, Materials Sciences and Engineering Division.
NM05.06: Nanoparticles, Nanocrystals and Nanostructures II
Session Chairs
Yves Huttel
Uwe Kortshagen
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 313
1:30 PM - *NM05.06.01
Gas-Phase Synthesis of Nanoparticles—Present Status and Perspectives
Yves Huttel 1
1 , Instituto de Ciencia de Materiales de Madrid, Cantoblanco, Madrid, Spain
Show AbstractThere is an increasing interest in the generation of well-defined nanoparticles (NPs) not only because of their particular properties resulting from their reduced dimensions, but also because they are promising building blocks for more complex materials in the fast growing nanotechnology [1]. As a consequence, the development of fabrication methods of high quality NPs is a key issue to follow the increasing demand of complex multifunctional nanoparticles for advanced applications [2].
In the first part of the talk, I will introduce the Gas Aggregation Sources (GAS) also known as Ion Cluster Sources (ICS) from an historical point of view. In particular I will present the different evolutions of the GAS along the last 20 years and discuss the advantages and limitations of the GAS that have been developed. Through examples I will illustrate how the GAS allow the synthesis of NPs with controllable and tunable chemical composition and structure while keeping a very good control over the size distribution, including alloyed and Core@Shell NPs [3].
In the second part of the talk I will present some limitations of the GAS (stability over time, yield, collection of NPs…) and discuss possible solutions. Finally I will address issues related to the scaling-up of the GAS for their application in industrial processes.
References
[1] U. Simon, Bonding them all, Nature Materials 12, 694 (2013).
[2] E. R. Zubarev, Nature Nanotechnology 8, 396 (2013).
[3] L. Martínez, et al., Langmuir 28, 11241 (2012); D. Llamosa, et al., Nanoscale 6, 13483 (2014). Y. Huttel, Gas-Phase Synthesis of Nanoparticles, Wiley, 2017.
2:00 PM - NM05.06.02
Real-Time X-Ray Scattering Study of the Synthesis of Nanoclusters by Plasma-Gas Condensation
Jeffrey Ulbrandt 1 , Yang Li 1 , Randall Headrick 1
1 , Univ of Vermont, Burlington, Vermont, United States
Show AbstractNanoclusters of various materials can be synthesized by magnetron sputtering through control of the background pressure in the range from 80 mTorr to 1 Torr, in a process called Plasma-Gas Condensation. An advantage of sputtering versus other physical deposition processes such as evaporation, is that the clusters acquire an inherent charge allowing characterization by mass spectrometry. Moreover, if the clusters are then deposited on a substrate, the formation of a nanostructured thin-film can be monitored by both real-time and post-deposition X-ray scattering. In this study, Grazing Incidence Small Angle X-ray Scattering (GISAXS) and X-ray Reflectivity (XRR) are used to analyze the spatial structure. The combination of mass spectrometry and GISSAXS techniques are directly sensitive to cluster mass and size respectively, thus making the calculation of accurate cluster density possible. We find that the clusters are denser than the bulk WSi2 compound with a density of 14.7 ± 1.8 g/cm3 versus a bulk density of 9.3 g/cm3. This is attributed to an enriched tungsten content. The films form a loose network of clusters and have a very low volume packing fraction of 15%. This packing fraction is predicted by the simplest Ballistic Deposition model, where particles are randomly deposited and stick on contact without further restructuring. Such nanostructured films have a large surface to volume ratios making them attractive for use in functional material such as thermoelectrics or dye-sensitized solar cells.
2:15 PM - NM05.06.03
Gas Phase Design and Synthesis of Mono-Metallic, Bi-Metallic and Tri-Metallic Nanoparticles
Mukhles Sowwan 1
1 , Okinawa Institute of Science and Technology, Okinawa Japan
Show AbstractMagnetron sputtering combined with inert gas condensation is a promising approach for single-step, chemical-free synthesis of metal and semiconducting nanoparticles . Herein, I will talk about the synthesis and growth modeling of monometallic, bi-metallic and tri-metallic nanoparticles using gas-aggregated co-sputtering from two or more different but neighboring elemental source targets. Considering that the nucleation process happens in the plasma region within a short distance from the sputtering targets, I will demonstrate that it is possible to control the size, chemical composition and shape by tuning several parameters that affect the plasma confinement. The nanoparticles were directly deposited and integrated into functional gas sensor devices with remarkable performance.
References:
1-Gas phase synthesis of multifunctional Fe-based nanocubes
J. Vernieres, S. Steinhauer, J. Zhao, A. Chapelle, P. Menini, N. Dufour, R. E. Diaz, K. Nordlund, F. Djurabekova, P. Grammatikopoulos, and M. Sowwan. Advanced Functional Materials 27 (2017) 1605328..
2-Engineering high-performance Pd core-MgO porous shell nanocatalysts via heterogenous gas-phase synthesis .V. Singh, C. Cassidy, F. A.-Pedersen, J. -H. Kim, K. Aranishi, S. Kumar, C. Lal, C. Gspan, W. Grogger, and M. Sowwan. Nanoscale 7 (2015) 13387-13392.
2-Heterogeneous Gas-phase Synthesis and Molecular Dynamics Modeling of Janus and Core-satellite Si-Ag Nanoparticles V. Singh, C. Cassidy, P. Grammatikopoulos, F. Djurabekova, K. Nordlund, and M. Sowwan. J Phys Chem C 118 (2014) 13869-13875.
3-Steinhauer, S., V. Singh, C. Cassidy, C. Gspan, W. Grogger, M. Sowwan and A. Köck (2015). "Single CuO nanowires decorated with size-selected Pd nanoparticles for CO sensing in humid atmosphere. Nanotechnology 26(17): 175502.
3:30 PM - *NM05.06.04
Mechanisms of Formation Fe Nanocubes by Inert Gas Condensation and Ag Nanoclusters in Ar Cryogenic Matrix
Flyura Djurabekova 1 , Junlei Zhao 2 , Ekaterina Baibuz 1 , Ville Jansson 1 , Kai Nordlund 2 , Jerome Vernieres 3 , Panagiotis Grammatikopoulos 3 , Stephan Steinhauer 3 , Mukhles Sowwan 3 , Lu Cao 4 , Richard Palmer 4
1 Helsinki Institute of Physics and Department of Physics, University of Helsinki, Helsinki Finland, 2 Department of Physics, University of Helsinki, Helsinki Finland, 3 , Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, Okinawa Japan, 4 Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham United Kingdom
Show AbstractMagnetron sputtering inert gas condensation is a versatile technique to generate nanoparticles of different nature and shapes. While commonly the nanoparticles grow spherically or in close to spherical shapes, some metal nanoparticles may grow in strongly non-spherical forms. For instance, we recently saw [1] that increased magnetron power may lead to the nanocubes, while the lower magnetron power was still resulting in spherical or mixed spherical and cubic nanoparticles. It is rather counter-intuitive to expect the formation of nanocubes under such circumstances taking into account the surface minimization considerations. However, it is important to understand why the nanoparticles can turn into nanocubes since the large surface area of nanoobjects is highly beneficial for many applications.
We address this question by applying the combination of three different techniques: experiment, Molecular Dynamics and Kinetic Monte Carlo simulations. By these method we study kinetics of the formation mechanism of iron nanocubes. Our results are in good agreement between the different methods and indicate that the cubic shape of iron nanoparticles is explained by the difference in the kinetic growth modes of (100) and (110) surfaces, rather than the surface formation energetics. The final shape is defined by condensation temperature in combination with deposition rate. We present also the full deposition rate--temperature diagram of iron nanocluster shapes as well as an analytical model predicting the temperature and deposition rate evolution in nanoparticles. Combined together, the diagram and the model can be used to tune the desired final shape of the grown iron nanoparticles.
A similar analytical model was developed to bridge the gap between theory and experiment to explain why it is possible to emit large Ag clusters from cryogenic Ar matrix in "Matrix Assembly Cluster Source", which was developed to enable industrial use of gas-phase synthesized nanoclusters. The method is based on Ar ion sputtering of a cryogenic solid Ar matrix containing embedded metal atoms. We show that irradiation of such a matrix enables the agglomeration of the particles even at cryogenic temperatures and describe the possible mechanism of emission of Ag nanoclusters from a solid Ar matrix, which we find out by a combination of experiment and computational methods. We show by molecular dynamics simulations that the cluster growth mechanism can be described as "thermal spike enhanced clustering" caused by multiple sequential ion impact events. The metal cluster emission is shown to be due to a combination of interface boiling and a matrix spring force effect. We propose an analytical model to describe the size-dependent cluster emission, which could lead to more precise control of nanocluster formation in experiments without losing the high production rate.
[1] J. Zhao et al., ACS Nano, 2016, 10 (4), pp 4684–4694
4:15 PM - NM05.06.06
Plasma-Based Gold Nanoparticle Synthesis
Alborz Izadi 1 , Rebecca Anthony 1
1 Mechanical Engineering, Michigan State University, East Lansing, Michigan, United States
Show AbstractNonthermal plasmas have demonstrated their promise in synthesis of semiconductor nanoparticles, ranging from intrinsic and doped elemental materials like Si and Ge to compound semiconductors such as ZnO and InP. More recently, plasmas have been used for growing core/shell semiconductor nanostructures and as in-flight surface-modification tools. As the versatility of plasma-based synthesis and processing evolves, it is important to expand the capabilities of these reactors for combined syntheses and multi-step processes.
One objective is to find a plasma-based route to noble metal nanomaterials which is compatible with plasma-based semiconductor nanocrystal processing. Such combined materials systems have been used for plasmonic enhancement of the semiconductor optical properties, shell-based encapsulation, and other novel applications. The problem is that it is challenging to physically link individual metal nanoparticles to semiconductor nanocrystals after synthesis, due to agglomeration. A step forward in solving this problem is to devise a vapor-phase route to metal nanoparticle synthesis that is compatible with vapor-phase plasma synthesis of semiconductor nanocrystals in a combined multi-stage process. Here we present our work on plasma-based gold nanoparticle synthesis, leading to vapor-phase-entrained gold nanocrystals.
In our method, we employ a radiofrequency (RF) plasma generated using a powered coil external to a quartz tube, together with a straight coaxial consumable grounded electrode, in this case made from a gold wire. Argon gas is flown through the tube at variable flowrates (0.2-1.2 slm), and the pressure inside is kept at 100-200 Torr. Gold nanocrystals with an average size around 5 nm are formed during the process and collected at the reactor exit. We characterized the nanocrystals using TEM, STEM, and EDS. The reactor variables affecting the gold nanoparticle production rate and physical properties include pressure, gas flowrate, RF power, plasma dimensions, and gold wire properties. To better understand the formation of the gold nanoparticles, we further characterized the reaction process using diagnostics on the gold wire, electrical probe measurements on the plasma, and optical emission spectroscopy. Our future work will explore the versatility of this process for other metal nanocrystals, and combining this reactor with other plasma-based nanocrystal syntheses for semiconductor nanoparticle decoration and encapsulation.
4:30 PM - NM05.06.07
Plasma Processing of Colloidal Nanocrystal Arrays—A General Strategy for the Synthesis of Large Area Inorganic Mesoporous Materials
Xinchun Tian 1 , Julia Chang 1 , Tiago Silva 2 , Fabian Naab 3 , Ludovico Cademartiri 1
1 , Iowa State University, Ames, Iowa, United States, 2 Institute of Physics, University of São Paulo State–UNESP, Sao Paulo Brazil, 3 Michigan Ion Beam Laboratory, University of Michigan–Ann Arbor, Ann Arbor, Michigan, United States
Show AbstractOur laboratory has been exploring in the past few years the interaction between plasmas and arrays of colloidal nanocrystals. We will focus in this talk about our use of this approach to create crack-free films of mesoporous oxides on cm^2 surfaces. This approach has several advantages over block-copolymer templated self-assembly of sol-gel reactions. (i) The material is bicontinuous, (ii) the solid phase is 100% crystalline, (iii) there is no microporosity, (iv) the surface chemistry of the solid phase can be tuned, (v) the specific crystallographic orientations of the solid/air interfaces can be controlled, in principle, during the synthesis of the building blocks, (vi) the composition of the material need not be dependent on the availability and reactivity of sol-gel precursors. These are all important factors for the utility of mesoporous materials in applications ranging from heterogeneous catalysis, to solar cells, to batteries, to membranes. And they are all very difficult targets to achieve by the very common surfactant templated mesoporous materials like MCM-41 and SBA-15.
We therefore characterized the porosity of these systems by paying special attention to anisotropic building blocks due to their potential for obtaining larger pore volumes and pore sizes that could be tunable by aspect ratio.
4:45 PM - NM05.06.08
Comparison of Nanocrystalline Iron Oxides with Different Valences Made by a Combination of a Plasma and a Hot Wall CVS Reactors
Alexander Levish 1 , Claudia Kuczera 1 , Markus Winterer 1
1 , University of Duisburg-Essen, Duisburg Germany
Show AbstractControlling the oxidation state of iron and the crystal structure of iron containing compounds is the key to improved materials such as iron oxide nanoparticles for cancer treatment or heterogeneous catalysis [1]. Iron oxides contain iron in different oxidation states and form different phases for one valence state (α-Fe3+2O2-3,β- Fe3+2O2-3, etc.).
Chemical vapor synthesis (CVS) allows the reproducible production of pure nanocrystals with narrow size distibution where particle formation and growth take place in the gas phase. Through the controlled variation of synthesis parameters CVS enables the synthesis of diverse iron oxide phases. Synthesis of different phases is accomplished by variating partial pressures of oxygen, residence time in the furnace and furnace power. In this study the energy for the CVS process is supplied by a hot wall furnace and a microwave plasma. The advantage of an plasma reactor as the first CVS stage is the fast and complete precursor decomposition at low temperatures. This results in a larger process window for the hot wall reactor in the second stage [2].
We study the comparison and combination of these two methods for the synthesis of crystalline iron and iron oxide nanoparticles with desired composition using Fe(acac)3 as precursor. Iron nanoparticles synthesized from Fe(acac)3 form a protective carbon matrix at the particle surface. Carbon imbedded iron nanoparticles were investigated [3]. The nanoparticles are examined regarding their structure, surface and valence by XRD, BET, TEM and XPS.
NM05.07: Poster Session
Session Chairs
Thursday AM, November 30, 2017
Hynes, Level 1, Hall B
8:00 PM - NM05.07.03
Au-Ir Core-Shell Like Nanoparticle Formation Using Femtosecond Laser Induced Plasma in Aqueous Solution
Teppei Nishi 1 , Yuichiro Hayasaka 2 , Takahiro Nakamura 3 , Shunichi Sato 3 , Takeshi Morikawa 1
1 , Toyota Central R&D Laboratories, Nagakute Japan, 2 The Electron Microscopy Center, Tohoku University, Sendai Japan, 3 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai Japan
Show AbstractNanoparticle formation by laser ablation has been developed because of the capability to produce nanoparticles without any chemical reagents. In particular, Nakamura and Sato reported that femtosecond laser irradiation of solution containing metallic salts can produce alloy nanoparticles having the same composition as metallic ions in liquid used as raw materials.1 Here we demonstrate spatial variation of energy state of Au-Ir core-shell like nanoparticles smaller than 50 nm prepared by femtosecond laser irradiation of mixed solution of H2IrCl6 and HAuCl4.
UV-Vis transmission spectra revealed that metallic ions used as raw materials in solution were reduced by femtosecond laser irradiation and nanoparticles were produced. As the Au concentration increases, optical absorption peaks attributed to surface plasmon resonance of Au nanoparticles were obviously increased. Elemental mapping by energy dispersive X-ray spectroscopy (EDS) revealed the formation of nanostructure like core-shell structure composed of Ir (core) and Au (shell) and a part of Ir was exposed to the surface. X-ray diffraction shows no peaks shift ascribed to alloy nanoparticle formation. It was expected that hetero interface influences the electronic state of Au and Ir and tried to investigate it by electron energy loss spectroscopy (EELS) analysis. EELS spectra show the spatial variation of electronic state. This result indicates that electronic state can be controlled by a hetero interface formation. The formation mechanism of core-shell like structure is discussed based on the UV-Vis absorption spectra. UV-Vis absorption spectrum of aqueous solution of H2IrCl6 shows peaks in the range from 400 nm to 800nm although that of aqueous solution of HAuCl4 shows peaks below 400 nm. As a result, IrCl62- can absorb the incident laser light by two photon process although AuCl4- can absorb by three photon process. Consequently, direct interaction between the laser light and IrCl6- is easily occurred. Then, AuCl4- and residual IrCl62- are reduced by reducing agents such as hydrogen radical produced by the interaction between femtosecond laser and water. Additionally, oxygen evolution reaction (OER) activity will be discussed.
This work was partly supported by Nanotechnology Platform Program (Hokkaido University) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
1. T. Nakamura, Y. Herbani, S. Sato, J. Nanopart. Res (2012)14:785.
8:00 PM - NM05.07.04
CVD Synthesis and Properties of c-BN/Diamond Composite Coatings
Stepan Linnik 1 , Alexander Gaydaychuk 1
1 High Technology Physics Research Institute, Tomsk Polytechnical University, Tomsk Russian Federation
Show AbstractWe report about the CVD synthesis of new nanocomposite c-BN/diamond films in AC glow discharge plasma. N2/CH4/(OCH3)3B/H2 gas mixtures were used as the precursor gas. The formation of the diamond phase promoted the formation of a metastable cubic boron nitride phase. Using this method, we obtained nanocomposite films with thickness up to 50 μm. The growth rate of such films in AC glow discharge reactor reached 5 µm/h. We also investigated the resistance of these coatings to high-temperature (up to 1000 oC) oxidation in comparison with classical diamond films. The structure of the resulting films have been thoroughly characterized concerning their morphology and structure by scanning electron microscopy and concerning their crystalline properties by X-ray diffraction and Raman spectroscopy. The developed technology may be very interesting for applications in the field of superhard wear resistant films deposition on cutting tools. Due to a higher (in comparison with diamond) resistance to oxidation and dissolution in ferrous metals, these composite coatings can be applied for the machining of almost any material.
8:00 PM - NM05.07.05
High Activity Heterogeneous Catalysts by Plasma-Assisted Chemical Vapor Deposition of Volatile Palladium Complexes on Biomorphic Carbon
Lisa Czympiel 1 , Sanjay Mathur 1 , Michael Frank 1
1 , University of Cologne, Cologne Germany
Show AbstractTransition metal-catalyzed procedures are very useful to the chemical industry, for example for the generation of pharmaceuticals or agricultural compounds. Several C C and C N bond formation reactions like the Heck-Mizoroki, Suzuki or Buchwald-Hartwig reaction are known and widely studied. Most studies have been focused on homogeneous catalysis but in recent years more and more attention has been given to heterogeneous catalytic systems. Precious metals immobilized on a biomorphic support can be easily removed leaving products virtually free of metal residues and more over the expensive catalysts can be reused in additional catalytic cycles. In the recent past there has been significant interest in bio-based composites as a result of growing environmental stewardship and increased requirements for green content in products. Due to the high surface-to-volume ratio of porous substrates derived from wood (Biomorphiccarbon - BioC), which is beneficial for the metal loading in solid supported catalysts, our research has been focused on the generation of new precious metal@BioC catalysts produced by chemical vapor deposition and wet chemical techniques.
We have created a precursor-library for various metal nanostructures like palladium, platinum, gold, nickel and copper. New palladium complexes based on allyl and alkenolate ligands were synthesized and structurally characterized. Combination of delocalized allylic sp2-hybridized carbon centers and a strongly binding N^O chelating unit (e.g. 3,3,3-trifluoro(pyridin-2-yl)propen-2-ol) offer promising combination of high volatility and thermal lability not commonly observed in noble metal precursors. Application of the new Pd compounds in plasma-assisted chemical vapor deposition (PE-CVD) demonstrates their clean and efficient decomposition pathways, which in conjunction to their intriguing stability in air made them efficient precursors to Pd films and clusters. PE-CVD of the palladium compounds on biomorphic carbon used as a porous substrate with high surface area and inter-connected channels delivered recyclable carbon-supported Pd catalysts (Pd@BioC), which showed excellent selectivity, stability and recyclability in C C coupling reactions. Application of the plasma assisted CVD process ensured the formation of very small nanoclusters exhibiting a better catalytic activity in C C coupling reactions in comparison to bigger clusters obtained through thermal chemical vapor deposition methods using the same precursor. This study highlights the importance of carefully choosing the activating source in chemical vapor deposition processes and its impact on the obtained material.
8:00 PM - NM05.07.06
Straightforward Deposition of Uniform Boron Nitride Coatings by Chemical Vapor Deposition
Jose Nocua 1 , Gerardo Morell 2
1 College of Education, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 2 Physics, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States
Show AbstractBoron nitride (BN) has a very high thermal conductivity and good thermal resistance. An addition, BN are very important in industrial applications involving surfaces in contact with molten materials. These applications require straightforward BN deposition methods that produce uniform coatings. Using borazine (B3N3H6) as a precursor, BN coatings were deposited on silicon substrates by chemical vapor deposition. The microstructure, composition, and morphology of the coatings were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electron energy loss spectroscopy (EELS). These characterizations show that the BN coatings deposited are uniform, predominantly of hexagonal structure and N-rich.
8:00 PM - NM05.07.07
Facile Production of Low-Dimensional Carbon Nanomaterials Using Solution Plasma System and Their Application to Conductive Paper
Byeong-Joo Lee 1 , Goo-Hwan Jeong 1
1 , Kangwon National University, Chuncheon Korea (the Republic of)
Show AbstractRecently, a plasma-assisted discharge system under water has attracted significant attention as a novel production method because it can be operated at room temperature without a bulky chamber and evacuation system. During over the decades, many works have focused on the production of nanoparticles using a solution plasma system.
We here demonstrate the production of low-dimensional carbon nanomaterials using a solution plasma system and their application to flexible conductive paper. The solution plasma system consists of two graphite electrodes and a beaker filled with ferritin-mixed deionized water. Ferritin molecules are used as the growth catalyst of the carbon nanomaterials. A high voltage of 15 kV at a frequency of 25 kHz is supplied to the electrodes using an alternating-current power source. The effects of the graphite rod diameters and the concentration of ferritin molecules are comparatively investigated. The produced carbon nanomaterials are characterized using Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. We confirmed the synthesis of graphitic platelets, onion-like structures, and carbon nanotubes. Finally, we fabricated flexible conductive papers using the produced materials with a good electrical conductance.
8:00 PM - NM05.07.08
Behavior of Surface Functionalization of Carbon Nanotubes and Graphene Films Using Atmospheric Pressure Plasma Jet System
Byeong-Joo Lee 1 , Goo-Hwan Jeong 1
1 , Kangwon National University, Chuncheon Korea (the Republic of)
Show AbstractThe low-dimensional carbon nanomaterials such as carbon nanotubes (CNT) and graphene have been attracted much attention due to its remarkable physical properties and potential applications in many fields. To modulate the physical and chemical properties, the plasma treatment was introduced as a powerful, facile, and efficient method, since the plasma process can be operated at room temperature, and the treatment time can be shortened owing to the highly active species present in the plasma.
Recently, the atmospheric pressure plasma treatment has attracted great attention as one of the most promising alternatives. Since this system is performed at atmospheric pressure and room temperature, and is not affected by the chamber size, it enables large-scale and continuous surface treatment of various materials.
We here demonstrate the behavior of surface functionalization of vertically-aligned CNT (VCNT) arrays and CVD-grown graphene films using atmospheric pressure plasma jet (APPJ) system.
The VCNT arrays were synthesized on Fe-deposited wafer using acetylene gas and the graphene was grown using methane gas by thermal CVD method. To modulate the surface functionality of the materials, the APPJ using nitrogen gas was ignited at high voltage of 15 kV and 25-kHz frequency. We varied the treatment time of the APPJ and inter-distance between plasma jet and CNT/graphene surface to systematically investigate the optimal condition of the APPJ system. We found that the hydrophobic nature of as-grown VCNT and graphene films were drastically changed to hydrophilic character through the simple APPJ treatment. According to the X-ray photoelectron spectroscopy, the formation of hydrophilic functional groups such as hydroxyl and carboxyl groups and nitrogen-doping-related functionalities such amine, pyrrolic-, and pyridinic-bonding was confirmed. The results prove that the APPJ system is a powerful candidate as facile and efficient method for surface modification of carbon nanomaterials.
8:00 PM - NM05.07.09
A Plasma-Based Route to GaN Nanocrystals
Rajib Mandal 1 , Alexander Ho 1 , Rebecca Anthony 1
1 , Michigan State University, East Lansing, Michigan, United States
Show AbstractGallium nitride (GaN) has been used in bulk form for the fabrication of light-emitting devices, transistors, and various other electronics. Bulk GaN has a band gap of 3.4 eV which has been advantageous for use in ultraviolet and blue emitting LED’s. Synthesis of GaN at the nanoscale can allow tunable emission wavelength via quantum confinement, and alloying with materials such as Indium allows for emission across the visible spectrum. In addition, nanocrystals can be assembled into thin films on arbitrary substrates, enabling new device morphologies such as stretchable or bendable displays.
Here we present a gas-phase-only plasma-based route to synthesis of GaN nanocrystals (NCs) with tunable size. This low-temperature approach to freestanding GaN NCs eliminates common issues of hazardous solvent use and defects caused by lattice mismatch between the GaN and the substrate, and allows for the deposition of GaN NCs onto substrates of various materials and morphologies. The plasma reactor was operated using 13.56 radiofrequency (RF) power at pressures between 5-15 Torr. Trimethylgallium and ammonia were used as precursor gases and argon was used as the background gas. Samples were collected either by inertial impaction or diffusion onto a substrate.
Several techniques were used to characterize the synthesized GaN including x-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), absorption spectroscopy, and photoluminescence (PL). XRD in conjunction with TEM indicated crystalline GaN with a hexagonal structure and average sizes of 3.5 nm and 4.9 nm depending on the reactor parameters. Investigation of the nanocrystal surface was carried out using FTIR. The FTIR spectrum displayed peaks corresponding to N-H, N-H2, and Ga-N of these N-H was the most prominent group at the surface. A 325 nm LED was used as the excitation source to observe PL for GaN NCs dispersed in oleic acid. We observed a PL peak near 375nm for the suspended GaN NCs.
However, the PL was relatively dim - the highly crystalline nanoparticles but weak PL suggested issues at the surface of the GaN NCs. To mitigate surface related issues with PL, we are investigating molecular surface functionalization after synthesis as well as integration of functionalization steps into the reactor in a multi-stage plasma process.
8:00 PM - NM05.07.10
Highly Sensitive Surface Enhanced Raman Spectroscopy Substrate with Tens Nanometer Quasi Period Nanostructures
Yuanhao Jin 1 , Qunqing Li 1 , Shoushan Fan 1
1 , Tsinghua-Foxconn Nanotechnology Research Center, Beijing China
Show AbstractWe introduce a simple and cost effective approach for fabrication of effective surface-enhanced Raman spectroscopy (SERS) substrate. It is proved that the as fabricated substrates shows excellent SERS effects in various probe molecules with high sensitivity to picomolar level detection and also good reliability. With a SERS enhancement factor beyond 108 and excellent reproducibility (less than 5%) of signal intensity, the fabrication of SERS substrate is realized on four inch wafer and proved to be effective in the application of pesticide residue detection. It is realized firstly through a fabrication of quasi period nanostructured silicon with dimension feature in tens nanometers using super-aligned carbon nanotubes networks as etching mask and then a large amount of hot-spots with nanometer gaps was formed through deposition of gold film. With rigorous nanostructure design, the enhanced performance of electromagnetic fields distribution for nanostructures is optimized. With the advantage of large area preparation in cost effective way, it is believed that as fabricated SERS substrate could be used in widespread actual applications where trace amounts detection is necessary.
8:00 PM - NM05.07.11
Etchability Dependence of InOx and ITO Thin Films by Plasma Enhanced Reactive Thermal Evaporation on Structural Properties and Deposition Conditions
Ana Amaral 1 2 , G. Lavareda 3 4 , C. Nunes de Carvalho 4 , V. André 2 , Yuri Vygranenko 4 , M. Fernandes 4 5 , Pedro Brogueira 1 2
1 , Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Lisboa Portugal, 2 , Centro de Física e Engenharia de Materiais Avançados (CeFEMA), Instituto Superior Técnico, Universidade de Lisboa, Lisboa Portugal, 3 , Departamento de Ciências de Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisboa Portugal, 4 , Centro de Tecnologia e Sistemas, Faculdade de Ciências e Tecnologia (CTS), Universidade Nova de Lisboa, Lisboa Portugal, 5 , Departamento de Engenharia Electrotécnica e de Computadores, Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Portugal, Lisboa Portugal
Show AbstractTransparent conductive oxides are widely studied because of their several applications in optoelectronic devices. In this work indium oxide (InOx) and indium tin oxide (ITO) thin films were deposited on glass substrates by plasma enhanced reactive thermal evaporation (PERTE) at different substrate temperatures. X-Ray diffraction shows the appearance of a peak around 2q=31° as the deposition temperature increases from room temperature to 190 °C, both for ITO and InOx.. AFM surface topography of the deposited films are consistent with the structural properties suggested by the x-ray spectra: as the deposition temperature increases, the surface changes from a finely grained structure to a material with a larger-sized grain or/and agglomerate structure of the order of 250-300 nm. The roughness Rq varies from 0.75 nm for the amorphous tissue to a maximum for 6.15 nm for the sample with the biggest crystalline grains. Raman spectra are also presented. The films were then submitted to two etching solutions with different chemical reactivity: i) HNO3 (6%), at room temperature; ii) HCl (35%): (40 °Bé) FeCl3 (1:1), at 40 °C. The dependence of the etchability of the films on the structural and deposition conditions is discussed.
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Micro Wrinkle and Nano Patterning Process on PDMS Substrate
Jun Ho Oh 1 , Ju Yeon Woo 1 , Sungwhan Jo 1 , Chang-Soo Han 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractIn the natural world, micro/nano hybrid structures are often found on the surface of natural systems, and they exhibit unique optical properties, like a morpho butterfly wings and rainbow beetles. Therefore, various studies about the hybrid pattern combining nano patterns onto micro-wrinkles have been tried. Generally, micro wrinkle would be created by ultraviolet-ozone (UVO) surface treatment or O2 plasma treatment, and the nano pattern could be formed by a soft lithography method. This patterning is performed by using a hard polydimetylsiloxane(h-PDMS), but requires complex, slow and high cost processes. In this study, a micro/nano hybrid structure was fabricated using a UVO or O2 hardening treatment method for micro wrinkle as well as imprinting method with a PDMS oil making for nano pattern for a simple, inexpensive and fast process.
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Modulation of Self-Organized Dot Structures by In Situ Annealing During Ion Beam Sputtering
Andres Redondo-Cubero 1 , Katharina Lorenz 2 , Javier Palomares 3 , Beatriz Galiana 4 , D. Bahena 5 , M. Garcia-Hernandez 3 , Luis Vázquez 3
1 , Universidad Autonoma de Madrid, Madrid Spain, 2 , Universidade de Lisboa, Bobadela Portugal, 3 ICMM, Consejo Superior de Investigaciones Científicas, Madrid Spain, 4 , Universidad Carlos III de Madrid, Leganés Spain, 5 Departamento de Física, CINVESTAV, México Mexico
Show AbstractIon beam sputtering (IBS) is a widespread technique that can be used for the production of nanopatterns in a large range of materials and scales [1], being silicon the most studied target material. In the last years, the key role of metal impurities for the initial formation of the pattern in mono-elemental targets has been clearly established [2], changing the field in a significant way. Still, several questions remain open, such as the segregation effect of metal silicides [3], the relevance of preferential sputtering for the different metal species [4], or the threshold metal concentration needed for nanopatterning at given experimental conditions. Most of these works are restricted to low energetic beams (0.5-5 keV) produced with conventional ion [5]. However, in order to have an appropriate control of the metal species and to enhance the features of the patterns (height, wavelength, metal content, etc. ) medium energy ion implanters are becoming essential.
In this communication, we will present our recent experimental works on IBS nanopatterning of Si at medium energies (20-160 keV) with simultaneous metal incorporation [6]. We evaluate the relevance of the compositional patterning in the dot formation for two metals (Fe and Mo) and two different ions (Xe and Ar). The irradiation was carried out in a high-flux ion implanter at different fluences, energies and temperatures (up to 400 °C). The morphology was studied using atomic force microscopy, resulting in a dot pattern for high fluences (1E18 cm-2). Metal content was determined with Rutherford backscattering spectrometry and the formation of silicides mapped with X-ray photoelectron spectroscopy. High resolution transmission electron microscopy was also used to prove the compositional patterning of the samples. Remarkably, the dot pattern is modulated by long-range corrugations, which can be controlled by the temperature. We will discuss the main differences arising from the different metal incorporation paths, paying special attention to the local metal arrangement required to trigger the pattern and form metal silicides.
1. J. Muñoz-García et al., Mater. Sci. Eng. R-Rep. 86, 1 (2014)
2. C. Madi et al., Phys. Rev. Lett. 101, 246102 (2008)
3. M. Engler et al., Nanotechnology 25, 115303 (2014)
4. R. Gago et al., Nanotechnology 25, 415301 (2014)
5. K. Zhang et al., Nanotechnology 25, 085301 (2014)
6. A. Redondo-Cubero et al., Nanotechnology 27, 444001 (2016)
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The Fabrication of Precise Nanopattern Array Using Nanoimprint Lithography and Hybrid Etching Technique
Sunghwan Jo 1 , Ju Yeon Woo 1 , Chang-Soo Han 1
1 , Korea University, Seoul Korea (the Republic of)
Show Abstract
Fabrication of nanoscale structure is very significant for many applications such as semiconductor memory, life science, biosensors and renewable energy etc. So current lithography technologies should be more advanced for achieving much lower cost and faster process for fabricating nanoscale features. Nanoimprint lithography (NIL) is attracting attention as a new alternative to make finer, faster and uniform nanostructures than conventional lithography. However, if we want to use this nanostructure as a mask, it is necessary to undergo an etching process. When the pattern size becomes tens of nanometers or less, it is difficult to etch the structure by a general plasma etching process such as reactive ion etching (RIE). Here we suggest a hybrid etching method combining oxygen RIE and argon ion sputtering method to avoid destroying the nanoimprinted nano-patterns. And we compared the conditions of the etched nanostructures between the conventional dry etching and the hybrid method. As a result, it was confirmed that novel method exhibited the lower destruction of the nanostructure under same etching of residual layers than that of the conventional etching method. These results show the possibility of making high-density nanoscale structure and device with nanoimprint lithography.
8:00 PM - NM05.07.15
Nanoripple Production on a-Si under Ar Irradiation
Alvaro Lopez Cazalilla 1 , Andrey Ilinov 1 , Laura Bukonte 1 , Joy Perkinson 3 , Michael Aziz 3 , Scott Norris 2 , Flyura Djurabekova 1 , Kai Nordlund 1
1 , University of Helsinki, Helsinki Finland, 3 , Harvard University, Cambridge, Massachusetts, United States, 2 , Southern Methodist University, Dallas, Texas, United States
Show AbstractIon beams are frequently used in industry for composition control of different materials as well as thin film deposition. It was noticed that low- and medium- energy ions at high fluencies may produce nanoripples and quantum dots on the irradiated surfaces. In the present work we focus our attention on the study of simulated irradiation of amorphous silicon (a-Si) sample with 1 keV Ar ions under different angles, taking into special consideration angles close to the grazing incidence [1]. Moreover, sequential 1 keV Ar irradiation is done in order to see the evolution of the surface.
This study has been carried out with Molecular Dynamics (MD), which provides tools to measure the stress generated in the simulation cell as well as the total displacement of the particles which compound the cell. MD results are compared with the results obtained using the Binary Collisions Approximation (BCA), following the previous work on this matter [2]. The results are subsequently analyzed with the numerical module Pycraters [3], which allows the prediction of the ripple wavelength. The calculated wavelength can be directly compared with the experimental observations.
[1] A. Lopez-Cazalilla, A. Ilinov, L. Bukonte, F. Djurabekova, K. Nordlund and S. Norris, submitted (2017)
[2] Scott Norris, Juha Samela, Laura Bukonte, Marie Backman, Flyura Djurabekova,
Kai Nordlund, Charbel S. Madi, Michael P. Brenner & Michael Aziz, Nature Communi-
cations 2, 276 (2011)
[3] Scott Norris, arXiv:1410.8489 [physics.comp-ph]
8:00 PM - NM05.07.16
Combinatorial Search of a Cu-Cr Composition Condition and Fabrication of a New Nanoporous Film by Dealloying of Cu-Cr
Yusuke Yoshii 1 , Junpei Sakurai 1 , Mizue Mizoshiri 1 , Seiichi Hata 1
1 , Nagoya University, Nagoya city Japan
Show AbstractWe have fabricated a nanoporous film having new properties by dealloying of Cu-Cr. At first, combinatorial search of a Cu-Cr composition condition for dealloying was conducted. A compositional range between 22 and 15 at.% Cr was investigated. The composition gradient (22-15 at.% Cr) of the 380 nm as-deposited film was immersed in 22.5% HNO3 for 15 h at room temperature. As a result, the initial Cr composition of 22-18 at.% became 33-80 at.% after Cu dealloying.
Moreover, the thickness of the film have not changed in this area before and after Cu dealloying. The location of less than 18 at.% of the initial Cr composition was absolutely dissolved due to the low Cr composition. The composition condition of Cu82Cr18, which produced the sufficient Cu dealloying, was used for a fabrication of a nanoporous film. A Cu82Cr18 film with an area with dimensions 2 mm×5 mm was fabricated on a glass substrate by co-sputtering for 35 min at 2.5 Pa of argon, at 175 W for the Cu target and 80 W for the Cr target. The so fabricated sample was immersed in 22.5% HNO3 for 20 min at room temperature. As a result, Cu was dealloyed from the as-deposited
Cu82Cr18 film, and its composition changed into Cu22Cr78. Furthermore, an appearance of the film changed from Cu brown to transparent appearance, and the dealloyed film was an insulation state. From a XRD analysis, some Cr2O3 peaks were newly observed and it indicates the transparency and the insulation state of the film are based on Cr2O3. A surface structure of the dealloyed film taken by FE-SEM showed some small cracks have formed throughout the film. This is because of an as-deposited internal stress, and dealloying process relieves this stress, and then small cracks have appeared on the surface. A surface structure such as cracks and pore sizes may originate from a difference between a coefficient of thermal expansion (CTE) of a film and that of a substrate, and it was studied that a Cu82Cr18 film was fabricated on a softer substrate (polyimide) by same sputtering condition, and Cu was dealloyed as well as the dealloyed film on the glass substrate. There was a difference in the tendency of the emergence of cracks between the film on the glass substrate and the one on the polyimide. A nanoporous structure with 20-40 nm pores was successfully obtained after dealloying, however large film cracking was observed when using the polyimide due to a high difference in CTE. Therefore, adjusting the difference between CTE of the nanoporous film and that of the substrate has a potential route to an elimination cracks created on the film surface, and which will be the future works. Summary, the nanoporous film, which has 20-40 nm pores and new properties such as the transparency and the insulation state, was fabricated by dealloying of binary alloy of Cu-Cr, and it is expected for use as a nanofilter or an absorbent.
8:00 PM - NM05.07.17
Deposition Rate Influence on Gas Sensing Response of Sputtered ZnO Thin Films
Y.N. Colmenares 1 , Valmor Mastelaro 1
1 , Univ of Sao Paulo, Sao Carlos Brazil
Show AbstractThe development of ZnO semiconductor gas sensors have become an important investigated issue due to the wide range of applications, the variety of responses and the high sensitivity and selectivity properties. Theoretical models and related experimental works indicated that the gas sensing response is fundamentally dependent of the surface morphology, particle size and grain boundary. This is mainly due to the available area for adsorption of gas molecules and the contribution of superficial irregularities to the conductivity of the entire material. With the use of a highly controllable deposition technique as sputtering, the main objective of this work is study the formation of nanostructured ZnO thin films with a superior gas sensing response, sensitivity and recovery times. ZnO thin films were obtained via RF-Magnetron Sputtering from a metallic zinc target and submitted to a subsequent ex-situ thermal oxidation in air atmosphere. The sputtering deposition is performed varying the substrate material, the deposition power and final thickness. The influence of the energy of sputtered Zinc atoms (or atomic clusters) in the thin film formation was studied by scanning electron microscopy where an important difference in the morphology and particle size is noted. Despite the variations in the grain growth dynamics, all samples presents a wurtzite crystalline structure, while XPS and EDS characterizations shows the absence of contaminants. Based on these results, we can assert that the initial size of metallic zinc microstructure has a more significant influence on the size of ZnO final microstructure than the conditions of thermal treatment. The gas sensing properties of thin films obtained from different depositions rates were followed by measuring the material electrical resistance, in presence of air with different ozone (O3) gas concentrations and during different exposure times. The relationship between the gas response and the surface morphology shows that the sample presenting the lowest grain size bring the higher gas response. This study allowed to observe the nanostructure and surface characteristics of ZnO thin films as a tunable factor for gas sensing properties. The power deposition with the best sensing response will be used for establish the conditions for deposition of zinc oxide doped thin films.
8:00 PM - NM05.07.18
Plasma Damage-Free Sputtering of Highly Transparent InSnTiO Films on PET Substrate for High Performance Flexible Thin-Film Heaters
Jae-Gyeong Kim 1 , Hyeong-Jin Seo 1 , Hae-Jun Seok 1 , Han-Ki Kim 1
1 , Kyung Hee University, Yongin-si Korea (the Republic of)
Show AbstractWe investigated the electrical, optical, mechanical and morphological properties of the InSnTiO films prepared using a linear facing target sputtering (LFTS) system. Due to the effective confinement of the high density plasma between facing targets and the position of PET substrate outside of plasma, we were able to obtain high performance InSnTiO films, even though they was sputtered at room temperature. To optimize plasma damage free sputtering conditions, the InSnTiO films were sputtered as a function of DC power, working pressure, target to target distance, and target to substrate distance. In addition, post oven annealing effect on the sheet resistance and optical transmittance of the InSnTiO films was investigated in detail. Furthermore, we examined the mechanical properties of the LFTS-grown InSnTiO electrodes using various bending test systems such as inner bending, outer bending, twisting, rolling and dynamic fatigue bending tests. To investigate its feasibility of LFTS-grown InSnTiO films as a flexible and transparent electrode for flexible and transparent thin film heaters (TFHs), InSnTiO-basded flexible TFHs were fabricated with a size of 50 × 50 mm2 using a two-terminal metal contact configuration. The time-temperature profiles and heat distribution analysis demonstrate that the performance of the flexible TFH with the oven annealed InSnTiO electrode is superior to that of a TFH with as-deposited InSnTiO electrode. The effective heat generation of the LFTS-grown InSnTiO film indicated that it is feasible to use InSnTiO film to create energy-efficient automobile windows, smart windows for BEMS, and energy efficient vinyl-houses.
8:00 PM - NM05.07.19
Constriction of Lattice Constant in Epitaxial Magnesium Oxide Film
Satoru Kaneko 1 , Takashi Tokumasu 2 , Rieko Sudo 3 , Shigeo Yasuhara 4 , Kazuo Satoh 5 , Masahito Kurouchi 1 , Manabu Yasui 1 , Akifumi Matsuda 6 , Mamoru Yoshimoto 6
1 , Kanagawa Institute of Industrial Science and Technology, Ebina Japan, 2 , Tohoku University, Sendai Japan, 3 , Sagamihara Surface Loboratory, Sagamihara Japan, 4 , Japan Advanced Chemicals, Sagamihara Japan, 5 , Osaka Research Institute of Industrial Science and Technology, Izumi Japan, 6 , Tokyo Institute of Technology, Yokohama Japan
Show AbstractSatoru Kaneko1,3, Takashi Tokumasu2, Rieko Sudo3, Shigeo Yasuhara4, Kazuo Satoh5, Masahito Kurouchi1, Manabu Yasui1, Akifumi Matsuda6, Mamoru Yoshimoto6
1) Kanagawa Institute of Industrial Science and Technology (KISTEC)
2) Tohoku University
3) Sagamihara Surface laboratory, SIC
4) Japan Advanced Chemicals
5) Osaka Research Institute of Industrial Science and Technology
6) Tokyo Institute of Technology
Epitaxial oxides on silicon (Si) substrate, as a buffer layer, allow high-quality of devices with a well-developed semiconductor technology. Magnesium oxides (MgO) we focused in this study is one of candidates as such a buffer, and it is known that MgO(001) epitaxially grows on Si(0010 with the relation of 45 degree rotation arrangement (MgO(100) // Si(010)) along in-plane direction despite of a large mismatch of ~22%. We prepared epitaxial MgO films deposited by using a pulsed laser deposition (PLD), and interestingly, epitaxial MgO(001) film on Si(001) substrate showed large constriction of lattice constant along both in-plane and out-of-plane directions with cubic on cubic arrangement (MgO(100) // Si(100)), instead of normal "45 deg. arrangement".
MgO was deposited on Si(001) substrate by using a slower Q-switched PLD system[1] with the fourth harmonic of 266 nm at the repetition rate of 2 Hz in relatively high oxygen atmosphere, and MgO target was placed with the distance of 30 mm from Si(001) substrate, and the size of Si and MgO target was both 10×10 mm. For two-step deposition[2], the Si substrate was not cleaned or immersed in any kind of HF solution; the surface of Si substrate was covered with a natural oxide layer. The thickness of the oxide layer was estimated to be ~0.4 nm by using an ellipsometer, assuming a refractive index of 1.46 for SiO2.
Epitaxial growth was verified by by X-ray diffraction (XRD) by using ordinal θ-2θ together with in-plane XRD. In previous studies, MgO thin film epitaxially grows in high vacuum conditions, in this study epitaxial MgO thin films grew in high oxygen pressure with the substrate temperature of ~700°C by both PLD and sputtering methods in our systems. The lattice constants of MgO films prepared by sputtering method were estimated to be ~4.09 Å, instead of 4.21 Å of bulk MgO. With contraction of lattice constants, lattice mismatch was increased with 45 deg arrangement between MgO and Si. However, with cubic on cubic arrangement, domain match was improved [3]. We will show the effect of lattice constants on defects in the epitaxial MgO films, and stability of MgO crystal on Si surface by suing theoretical calculation such as ab initio method.
[1] S. Kaneko, T. Nagano, K. Akiyama, T. Ito, M. Yasui, Y. Hirabayashi, H. Funakubo, and M. Yoshimoto: J. Appl. Phys. 107 073523 (2017).
[2] S. Kaneko, Y. Shimizu, and S. Ohya, Jpn. J. Appl. Phys. 40 4870 (2001).
[3] S. Kaneko, H. Funakubo, T. Kadowaki, Y. Hirabayashi, and K. Akiyama EPL 81 46001 (2008).
8:00 PM - NM05.07.20
A XPS Study of Pt Single Atoms Dispersed on a Graphene Support Using Plasma Sputtering
Kenji Yamazaki 1 , Yosuke Maehara 1 , Kazutoshi Gohara 1
1 , Hokkaido University, Yokohama Japan
Show AbstractSingle metal atoms have engendered much interest in the field of single-atom catalysis, which constitutes a new frontier in catalysis research. One simple and fundamental question asked in this new field is whether catalyst performance can be enhanced by the single isolated atoms of expensive metals. However, selective fabrication of isolated single metal atoms has been challenging, because the atoms tend to aggregate during fabrication processes on support materials [1]. Thus the characterization of the chemical and electron states of single atom metals has been difficult due to the entanglement of complex information arising from isolated single atoms and atoms complexed in other structures such as clusters and nanoparticles. To overcome these limitations, we herein synthesized platinum (Pt) single atoms on a graphene support by the plasma sputtering method. We confirmed that 99% of the Pt atoms were isolated on the graphene by aberration-corrected TEM observation. We also confirmed that Pt single atoms were uniformly dispersed over a 1 mm diameter, a large enough area to characterize the chemical properties by a spectroscopic method. In this presentation, we report the unique electron state of Pt single atoms by XPS measurement.
Graphene films were grown by a CVD method on a copper substrate. it was transferred onto a carbon-supported Cu TEM grid. We deposited single atoms of dispersed Pt onto the prepared graphene by plasma sputtering using a pure Pt thin film. TEM and STEM observations of Pt single atoms were performed by an FEI Titan Cubed 60-300 TEM at 80 KV equipped with image and probe correctors. XPS analysis was conducted on a JEOL JPS-9200. The peak position and intensity of Pt 4f peaks were confirmed between single atoms and nanoparticles in the Pt dispersion. The measured spectrum was calibrated with respect to the C1s peak at 284.2 eV.
In XPS measurement, the Pt 4f-binding energy in dispersed Pt single atoms was significantly shifted to an energy higher than that of Pt clusters, nanoparticles, or bulk Pt substrate. The peak positon was 72.6±0.4eV. We observed the coexistence of Pt single atoms, clusters, nanoparticles, and island structures at longer sputtering time. Under this condition, the Pt 4f peaks could be separated into two components. The lower binding energy component become larger at the longer sputtering time. Therefore, the large peak shift represented the specific electron state of Pt single atoms. We did not confirm the significant change of XPS peaks of other elements such as C, O, and Si which come from TEM Grid. The intensity and position of O 1s peaks were not changed by the Pt structure. Therefore, we considered that this significant shift in Pt 4f-binding energy was not attributable to the oxidation of Pt atoms. In conclusion, we revealed the unique electron state of single Pt atoms by XPS measurement and TEM observation.
[1] J. Liu, ACS Catal. 2017, 7, 34−59.
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Plasmon Nanoantenna Integrated CdSe Quantum Dot-ZnO Photodetector
Jieun Park 1 , Eunji Song 1 , Manjeet Kumar 1 , Vishwa Bhatt 1 , Ju-Hyung Yun 1
1 , Incheon National University, Incheon Korea (the Republic of)
Show AbstractThe photodetectors play an important role in the development of technologies with the wide range of applications in the field of cameras, non-destructive testing, mimicking artificial eye, and optical communication. Present research scenario on photodetectors has been mainly centred on nanostructured materials which are the key factors of device fabrication. The choice of an appropriate material with well-defined properties plays the key role for the fabrication of photodetectors which can detect the different ranges of the electromagnetic spectrum. In this work we have fabricated Ag/CdSe QDs/ZnO based photo detectors. The ZnO films (200 nm) were deposited on a glass substrate using RF magnetron sputtering. Then, CdSe based quantum dots (QDs) were deposited on ZnO film as a light absorbing and charge transfer material to enhance the photo response of ZnO based metal-semiconductor-metal (MSM) photo detector. CdSe QDs were uniformly dispersed on ZnO MSM photodetector using spin cast (800 rpm for 30sec) method. We have investigated the quantum confinement effect of CdSe QDs using photoluminescence and absorption spectrum. The results reveal that the CdSe QDs has an excellent quality and homogeneously dispersed over the film surface. Due to the lack of capability for light absorption, plasmon nanoantenna was incorporated on QD-ZnO MSM photo detector. Therefore, silver nanoparticles (Ag NPs) were deposited on QD-ZnO photo detector using the thermal evaporation method. Fabricated Ag NP/ZnO nanoantenna were investigated to enhance the surface plasmon effect. The size and distribution of Ag NPs were controlled to have a resonance peak within 400~500 nm of wavelength, where QDs show the weakest light absorption. Ag NP/ZnO nanoantenna has a Plasmon resonance peak at 460nm of wavelength. After the dispersion of the CdSe QDs on Ag NP/ZnO surface, resonance peak is shifted to 526nm due to the change of dielectric constant of CdSe QDs.
The spectral response (SR) of three samples - bare MSM photodetector, MSM device with QDs, and QDs combined with plasmon nanoantenna were investigated, systematically. QDs decorated ZnO MSM device has 41 times of improvement in SR at 400nm of wavelength compared with a reference sample, which attributed to charge transfer from QD into the ZnO surface. When plasmonic structure was combined with QDs-ZnO MSM device, it has been observed that ~30-56 times of SR increased at 455nm to 560nm of wavelength, compared to the sample without plasmon structure. The increase of SR in a narrow band (peak 505 nm) is identical with the resonance peak position of nanoantenna (peak position: 526 nm). The improved SR in plasmon nanostructure on QDs based ZnO MSM photodetectors is attributed to surface-plasmon-resonance effect and charge transfer (tunneling) from the QDs to the ZnO.
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Mechanical Reliability of Al-Doped-Zn Oxide Thin Film Deposited on Polyimide Supports Using Ex Situ Oxygen Plasma Assisted-Atomic Layer Deposition at Low Temperature
Gyeong Beom Lee 1 , Seung-Hak Song 1 , Myeong-Woo Lee 1 , Yun-Jae Kim 1 , Byoung-Ho Choi 1
1 Mechanical Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractAbstract: Due to the spread of flexible displays, polymer materials, which are a typical substrate material, have been attracting much attention because of good flexibility, balanced mechanical properties, and great processability. Polypropylene (PP) and polyethylene terephthalate (PET) are promising substrate materials to replace conventional glass materials to be used in flat panel flexible display. However, these materials have some drawbacks of being vulnerable to heat. In this study, transparent polyimide (TPI) substrate is considered to deposit AZO thin film because of its transparency, high bendability and excellent thermal resistance. Moreover, studies of AZO thin film deposition on transparent polyimide substrate using ALD process have been scarcely reported yet. In this study, the deposition process parameters of AZO thin film, i.e. process temperature, alumina doping and plasma treatment, are optimized based on transparent electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), and the mechanical reliability of AZO thin film on TPI substrate is also evaluated. The optimization of AZO on TPI is performed by controlling the doping ratio Al and Zn atoms, and mechanical stability is evaluated with various mechanical characterizations techniques. It is observed that the sheet resistance of AZO 19:1 grown on TPI surface is showing the optimized value, i.e 294 ohms/sq. Nano scratch results reveal that the 1st critical load can be increased by surface hardening and strong adherence as function of process temperatures and plasma treatments. It is also observed that the strain at crack initiation is improved from 0.58% to 0.82% by varying the doping ratio of AZO.
8:00 PM - NM05.07.24
Plasma-Assisted and Thermal Atomic Layer Deposition of Electrochemically Active Li2CO3
Norah Hornsveld 1 , Brecht Put 1 2 , Erwin Kessels 1 , Philippe Vereecken 2 3 , Mariadriana Creatore 1
1 Applied Physics, Eindhoven University of Technology, Eindhoven Netherlands, 2 , Imec, Leuven Belgium, 3 Microbial and Molecular Systems, KU Leuven, Leuven Belgium
Show AbstractLi2CO3 is considered a potential electrode passivation film in lithium ion batteries and electrolyte material for chemical sensors and fuel cells. Also, it widely used as a building block for the fabrication of electrodes and electrolytes or as additive to improve electrode performance. This is attributed to its purely ionically conductive behavior and good electrochemical stability. Despite its widespread usage, there are few studies that focus on its characterization.
With the trend of manufacturing miniaturized devices that have smaller size, weight and lower power consumption, thin film fabrication techniques are a good choice. In this work, plasma-assisted and thermal ALD were adopted to grow Li2CO3 films between 50 and 300 °C using lithium tert-butoxide as precursor and O2 plasma and H2O/CO2 as co-reactant(s), respectively. Critical parameters such as film stoichiometry, morphology and ionic and electronic conductivities were evaluated for Li2CO3 films. The selected diagnostics are: Spectroscopic Ellipsometry, X-ray Diffraction, Scanning Electron Microscopy and Impedance Spectroscopy.
Stoichiometric Li2CO3 films can be deposited with both processes, although unlike what has been shown in literature (J. Phys. Chem. C, 118, 27749−27753), the stoichiometry of the plasma-assisted ALD films was found to be temperature and O2 plasma exposure time dependent. Specifically, a shorter O2 exposure time and a substrate temperature of ≤ 200 °C lead to stoichiometric Li2CO3, while at higher temperatures Li2O was deposited and further promoted by prolonging the O2 plasma exposure time. The introduction of Li2O in the films reduces film crystallinity and increases film non-uniformity which lead to a decrease in ionic conductivity.
For both thermal and plasma ALD films, the impedance response shows a behavior characteristic of a solid electrolyte, although differences were observed due to differences in film morphology. The plasma ALD films, which show a columnar structure, have a higher conductivity value compared to thermal ALD films. However, we hypothesize that liquid electrolyte contacts the individual grains, leading to significant increase in contact area. An ion conductivity in the order of 10-10 S/cm was obtained for both plasma and thermal ALD after normalizing the fitted conductivity value to the ratio of the different effective surface areas. The Li-ion conductivities found here are in line with literature values predicted by modelling studies.
The ionic conductivity was verified using dry solid-state impedance spectroscopy measurements. The activation energy of diffusion was determined to be approximately 0.77 eV, again in line with literature values (J. Phys. Chem. C, 117, 8579–8593). In addition, studies are ongoing to evaluate the electronic conductivity by DC-polarization measurements. Moreover, the performance of Li2CO3 as electron passivating film will be tested in a half cell (Si, LiMn2O4) and studied for cyclability and rate performance.
8:00 PM - NM05.07.25
Synthesis of α-MnS Hierarchical Nanostructures by Chemical Vapor Deposition Technique
Angela Luis Matos 3 4 , Brad Weiner 2 5 , Gerardo Morell 1 6
3 Physics, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 4 , Institute for Functional Nanomaterials, San Juan, Puerto Rico, United States, 2 Chemistry, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 5 , Institute for Functional Nanomaterials, San Juan, Puerto Rico, United States, 1 Physics, Univ of Puerto Rico at Rio Piedras, San Juan, Puerto Rico, United States, 6 , Institute for Functional Nanomaterials, San Juan, Puerto Rico, United States
Show Abstract
MnS is a wide band gap (3.1 - 3.7 eV) p-type direct semiconductor that exists in three crystallographic polymorphs; the green α-MnS is the most stable with a rock-salt crystal structure, and the two metastables zincblende (β-MnS) and wurzite (γ-MnS) crystals structures. The magneto-optical, electric and structural properties of MnS makes the material promising for a wide range of technological applications such as selective coating solar cells, electrodes to fabricate flexible all-solid state supercapacitors, electrodes for Li-ion batteries, contrast agent for MRI, LED devices, among others. The synthesis of inorganic nanostructures with controllable phase and specific morphologies (tubular, spherical and cage-like) with unique optical, electrical and structural properties has allured increased interest owing to their potential applications in drug delivery, sensors, filters and coatings. [α, γ, or β]-MnS structure materials usually have been synthesized by chemical solutions method just as solvothermal and hydrothermal techniques. However, our method in this work consists in the synthesis of free standing α-MnS hierarchical nanostructures by Chemical Vapor Deposition technique, which is suitable to prepare electrodes for Li-ion batteries. In this presentation, we discuss: a) the growth mechanism of α-MnS by Chemical Vapor Deposition technique; b) its structural, morphological, and compositional characterization; and c) Photoluminescence spectra.
8:00 PM - NM05.07.26
Low Temperature Synthesis of Ternary Metal Phosphides Using Plasma for Asymmetric Supercapacitors
Hanfeng Liang 1 , Chuan Xia 1 , Qiu Jiang 1 , Appala Gandi 1 , Udo Schwingenschlogl 1 , Husam Alshareef 1
1 , King Abdullah University of Science and Technology, Thuwal, Jeddah Saudi Arabia
Show AbstractWe report a versatile route for the preparation of metal phosphides using PH3 plasma for supercapacitor applications. The high reactivity of plasma allows rapid and low temperature conversion of hydroxides into monometallic, bimetallic, or even more complex nanostructured phosphides. These same phosphides are much more difficult to synthesize by conventional methods. Further, we present a general strategy for significantly enhancing the electrochemical performance of monometallic phosphides by substituting extrinsic metal atoms. Using NiCoP as a demonstration, we show that the Co substitution into Ni2P not only effectively alters the electronic structure and improves the intrinsic reactivity and electrical conductivity, but also stabilizes Ni species when used as supercapacitor electrode materials. As a result, the NiCoP nanosheet electrodes achieve high electrochemical activity and good stability in 1 M KOH electrolyte. More importantly, our assembled NiCoP nanoplates//graphene films asymmetric supercapacitor devices can deliver a high energy density of 32.9 Wh kg−1 at a power density of 1301 W kg−1, along with outstanding cycling performance (83% capacity retention after 5000 cycles at 20 A g−1). This activity outperforms most of the NiCo-based materials and renders the NiCoP nanoplates a promising candidate for capacitive storage devices.
8:00 PM - NM05.07.27
Development of Co-Sputtering Method Using Open-Air Micro-Plasma Jet and Its Application to Synthesis of Binary Compound Materials
Yoshiki Shimizu 1 2 , Yukiya Hakuta 2 1
1 Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan, 2 Advanced Operando-Measurement Technology Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Kashiwa Japan
Show AbstractThe authors have been studying the application of atmospheric-pressure micro-plasma jet operated in open air (open-air micro-plasma jet) to material processing. Regarding application to synthesis of materials such as nanoparticle (NP) and thin film, we have been investigating the method using metal wire as raw material. In this method, The metal wire, placed in the discharge tube, is sputtered by the plasma, and resultant metal vapor is condensed on the substrate placed in open air. Up to now, we have demonstrated the synthesis of NPs and thin films of single-component metal such as gold [1,2], and oxide such as tungsten oxide [3]and molybdenum oxide [4] by feeding small amount of oxygen gas into the plasma. Recently, we are studying the application of this method to synthesis of binary compound materials by concurrent sputtering of two different metal wire in the discharge tube. In this paper, we will present synthesis of Au-Sn alloy in this method.
The open-air plasma jet, driven with ultrahigh frequency (UHF, 450 MHz), was employed in this study. Configuration of the experimental setup was based on the original setup [1]. Au wire and Sn wire were inserted inside the discharge tube. In order to concurrently sputter both Au and Sn wires, whose vapor pressures largely differ from each other, the diameters of Au and Sn wires, the insertion depth toward the discharge tube outlet, and the plasma working conditions were optimized. Typically, the plasma was pulsingly generated by applying pulse-modulated UHF voltage with flowing H2 and Ar mixture gas. The resultant material was directly deposited on Si-wafer or thin carbon film, placed 5 mm downstream from the discharge tube outlet.
The characterizations by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) reveal that NPs, with diameter of 2-3 nm and composed of both Au and Sn, were formed under certain condition. In contrast, conditions, where Au-NPs or Sn-NPs were selectively formed, were found. The details of the conditions to selectively synthesize Au-Sn alloy will be presented in symposium.
References
[1] Y.Shimizu, AIP Advances 7, 015316 (2017)
[2] Y. Shimizu, K. Kawaguchi, T. Sasaki and N. Koshizaki, Appl. Phys. Lett. 94, 191504 (2009).
[3] Y. Shimizu, A. C. Bose, D. Mariotti, T. Sasaki, K. Kirihara, T. Suzuki, K. Terashima and N. Koshizaki, Jpn. J. Appl. Phys. 94, 191504 (2006).
[4] A. C. Bose, Y. Shimizu, D. Mariotti, T. Sasaki, K. Terashima and N. Koshizaki, Nanotechnology 17, 5976 (2006).
8:00 PM - NM05.07.28
Silver Nanowires and Nanodendrites Synthesized by Plasma Discharge in Solution for the Catalytic Oxygen Reduction in Alkaline Media
SangYul Lee 1 , Jung-Wan Kim 2 , Sung-Min Kim 1
1 , Korea Aerospace University, GoYang Korea (the Republic of), 2 Division of Bioengineering, InCheon National University, InCheon Korea (the Republic of)
Show AbstractSilver nanowires and nanodendrites are synthesized using the submerged plasma discharge without the involvement of any chemicals. The silver architecture relies on the electron density in plasma that could enable Ag ions to be reduced instantaneously to generate a large number of small Ag nanoparticles. With low electron density of 7.1 10-22 m-3, the Ag nanowires with the corrugated structure induced by twinning and stacking faults are formed along the entire longitudinal <111> direction. However, with high electron density 13.7 10-22 m-3, the Ag nanodendrites with defect-free structure are constructed. Due to the unique structure composed of twins and stacking faults, the Ag nanowires showed a specific current density of 2.7 times higher than the Ag nanodendrites towards oxygen reduction reaction. This work not only suggests a synthetic route to the formation of nanowires with structural defects but also offers the rational design of electrocatalysts with enhanced catalytic activity.
8:00 PM - NM05.07.29
Particle Temperatures and Aerosol Dynamics in a Spatially Characterized Low Temperature Plasma Reactor
Necip Uner 1 , Elijah Thimsen 1
1 , Washington University in St. Louis, Saint Louis, Missouri, United States
Show AbstractLow temperature radio frequency (RF) plasmas have been successfully utilized for synthesizing crystalline and monodisperse semiconductor and metal nanocrystals [1]. The crystallinity of the particles is usually attributed to the selective heating of particles in the plasma. It has been proposed that particles can be heated up to temperatures of 1000 K, although the gas temperature is much lower. On the other hand, monodispersity is thought to be caused due to Coulombic repulsion arising from unipolar negative charging of particles. Recently, it has been shown that particles vaporize in low temperature plasmas (LTP), and the re-condensation of the resulting vapor on particles can make the size distribution more monodisperse [2].
Many distinctive designs of the plasma reactors have been presented for nanomaterials synthesis. Since each design will have a unique distribution of plasma parameters and residence time distributions, the products coming out of these reactors are expected to be different. This work focuses on the aerosol dynamics in the flow-through reactor, which proved to be successful and flexible for nanomaterials synthesis[3]. The reactor offers relatively uniform particle residence times, high production rates, and continuous operation.
First, a thorough characterization of the reactor in terms of the plasma parameters, i.e. electron temperature, ion density and gas temperature, will be presented. By using a Langmuir double probe, electron temperature and ion density were measured as a function of input RF power, pressure and axial position. Gas temperatures were determined with help of a fluorescence decay probe. The reactor was found to have a distinct axial distribution of ion density and gas temperature, with the region in the vicinity of the powered electrode having 5 times higher ion density than the rest of the plasma. Gas temperatures were found to be significantly higher than room temperature at moderate powers.
The obtained plasma parameters were used in a particle heating/aerosol dynamics model, which describes the vaporization-condensation, nucleation, charging, diffusion and particle heating phenomena occurring inside plasma during synthesis. The size distributions of the final aerosol and reactor yields will be elaborated. Comparisons with experiments involving metal nanoparticles will be given.
[1] U. R. Kortshagen, R. M. Sankaran, R. N. Pereira, S. L. Girshick, J. J. Wu, and E. S. Aydil, “Nonthermal Plasma Synthesis of Nanocrystals: Fundamental Principles, Materials, and Applications,” Chem. Rev., vol. 116, no. 18, pp. 11061–11127, Sep. 2016.
[2] N. B. Uner and E. Thimsen, “In-Flight Size Focusing of Aerosols by a Low Temperature Plasma,” J. Phys. Chem. C, Jun. 2017.
[3] L. Mangolini, E. Thimsen, and U. Kortshagen, “High-Yield Plasma Synthesis of Luminescent Silicon Nanocrystals,” Nano Lett., vol. 5, no. 4, pp. 655–659, Apr. 2005.
8:00 PM - NM05.07.30
One-Step Synthesis of Nanostructured Co3O4 by Reactive Spray Deposition Technology for Efficient Electrochemical Water Splitting
Yang Wang 1 , Yang Wu 1 , Peter Kerns 1 , Steven Suib 1 , Radenka Maric 1
1 , University of Connecticut, Storrs, Connecticut, United States
Show AbstractElectrochemical water splitting is essential to the development of the hydrogen economy because it can provide a stable hydrogen supply with high efficiency. Oxygen evolution reaction (OER) (4OH− → O2 + 2H2O + 4e− in alkaline media) is one of the two half reactions in water electrolysis. However, the sluggish kinetics of the four-electron oxidation reaction make OER at the anode often require significant electrochemical overpotential. In order to overcome the large overpotential, the use of electrocatalysts is necessary. Currently, the most active OER electrocatalysts are iridium and ruthenium based compounds, but the high cost associated with these materials make them essentially impractical to use. Thus, it is critical to develop a catalyst free of noble metals but still demonstrates high electrochemical activity. Co3O4 is considered as one of the promising candidates due to its multivalence and high corrosion stability. Nanostructured Co3O4 with high surface area and large porosity further enhances the electrocatalytic OER activity because the diffusion of reactive species is promoted by increased accessibility to active sites, and because the transport path lengths of electrons are reduced for improved electronic conductivity.
In this study, nanostructured Co3O4 is synthesized via a simple and rapid flame based method, namely reactive spray deposition technology (RSDT). This novel synthesis route is a single-step continuous process, offering the advantage of low cost and scalability. In this process, a solution of dissolved cobalt precursor in organic solvents is fed through an atomization nozzle and the resulting aerosol spray is ignited to generate a turbulent flame. The precursor rapidly decomposes in the high temperature flame, followed by phase transition to vapor and homogeneous reactions to form oxides. The synthesized Co3O4 nanoparticles are directly deposited onto a substrate to form the electrode which serves as the anode for the electrochemical water splitting reaction. The objective of this work is to demonstrate high electrocatalytic activity with low cost catalyst.
8:00 PM - NM05.07.31
Large Area Black Gold Nanoparticle/Cellulose System for High Performance Solar Steam Generation at Low Illumination
Quoc Chinh Tran 1 , Sumin Lee 1 , Ilsun Yoon 1 , Ho Suk Choi 1
1 , Chungnam National University, Daejeon Korea (the Republic of)
Show AbstractRecently, the black plasmon absorber has attracted much attention as an effective material for generating solar-steam. However, conventional black plasmon absorbers are generally small, rely on high optical density systems, and also have relatively low efficiency due to high heat loss through convection, conduction and radiation. To solve this problem, we have developed a strategy for producing highly effective black plasmon absorber based on cellulose filter paper with hydrophilic, porous, high water absorption capacity and high water diffusion capacity. In this strategy, a black plasmon absorber was fabricated by immobilizing gold nanoparticles on a cellulose filter using a dry plasma reduction method. The fabricated black plasmon absorber adhered onto the foam with excellent thermal insulation, which not only naturally floated on the surface of the water, but also reduced heat loss due to conduction and radiation. Applying it to solar-steam generation, we achieved solar conversion efficiencies of about 97% at 3 sun intensities (3 kWm-2) and even near 100% efficiency at 1 sun intensity. Therefore, this strategy is expected to greatly improve solar energy harvest.
8:00 PM - NM05.07.32
In Situ Volumetric Nanoparticle Detection with Coherent Rayleigh-Brillouin Scattering
Alexandros Gerakis 1 , Mikhail Shneider 2 , Brentley Stratton 1 , Y Raitses 1 , Shurik Yatom 1
1 , Princeton Plasma Physics Laboratory, Princeton, New Jersey, United States, 2 Mechanical & Aerospace, Princeton University, Princeton, New Jersey, United States
Show AbstractWe report on the development and application of a new laser diagnostic for the in situ detection of large molecules and nanoparticles. This four wave mixing diagnostic technique relies on the creation of an optical lattice in a medium due to the interaction between polarized particles and intense laser fields. This diagnostic was already successfully demonstrated in atomic and molecular gaseous environments, where the different gas polarizabilities and pressures were successfully measured. Finally, using this diagnostic technique, we demonstrate the first in situ measurement of nanoparticles with dimensions of few nanometers, number densities in the order of 1012 cm-3, produced in an graphitic arc discharge.
8:00 PM - NM05.07.33
Enhanced Light Extraction Efficiency in White Organic Light Emitting Diode with Randomly Arrayed Void Structured Substrate
Kwan Kim 1 , Kyung-Hoon Han 2 , Yangdoo Kim 1 , PilHoon Jung 1 , Junho Jun 1 , Heon Lee 1
1 , Korea University, Seoul Korea (the Republic of), 2 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractOrganic light emitting diode (OLED) is expected as display and solid state lighting due to fast response, high color quality, applicability to flexible substrate and potentially low price. But, Outcoupling efficiency of OLED is still under 30% because of waveguide at glass/ITO interface and air/glass interface, surface plasmon polaritons (SPP) loss at organic/metal interface and internal absorption of materials. Light extraction efficiency still needs to be improved to be competitive in industrial area. Light extraction methods are classified with target modes to external light extraction for substrate mode and internal light extraction for waveguide and SPP mode. External extraction methods have been reported with micro lens array, rough surface and luminaire etc. but, have blurring effect at display panel. Internal extraction methods have been reported as low index layer, photonic crystal, high refractive index substrate, low index grid, Bragg grating, randomly dispersed nano-pillar array, nano-particles with thin electrode and moth eye but, is still remained challengeable because of largely confined lights, reliability of material, and availability at commercial display pixel etc.
When it comes to white OLED for illumination, brightness is emphasized rather than image quality, we focused on improving light extraction efficiency. To achieve enhancing light extraction from OLED substrate, we inserted TiO2 randomly arrayed void due to its high refractive index property. In this report, randomly arrayed void structure was utilized as light extraction structure. TiO2 void pattern has little periodicity or random distribution. This void structure was expected to extract WGM (waveguide mode) and has good spectral distribution with viewing angles.
In this paper, TiO2 void structured white OLED was fabricated to enhance light extraction efficiency by extracting wave guide modes. To fabricate TiO2 void structure, we formed randomly arrayed PBMA (Poly benzyl methacrylate) pillar via nanoimprint lithography. After subsequent reactive ion etching process of PBMA residual layer, TiO2 nanoparticle resin was used to planarization of random pillar pattern and annealing process was performed at 500 Celsius to remove PBMA pillar pattern. TiO2 was already reported as high refractive index material which is used to extract internal light reflection of OLED. Enhancement ratios of TiO2 void device were 3.67 (current efficiency) and 3.68 (power efficiency).
8:00 PM - NM05.07.34
Hierarchical Ttanium Nitride Nanostructures as Low-Pt Catalyst Scaffolds for DMFC Cell Reactions
Andrea Perego 3 1 , Giorgio Giuffredi 3 1 , Piero Mazzolini 3 , Filippo Bossola 2 , Vladimiro Dal Santo 2 , Andrea Casalegno 1 , Fabio Di Fonzo 3
3 Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Milan Italy, 1 Department of Energy, Politecnico di Milano, Milan Italy, 2 Istituto di Tecnologie Molecolari, CNR, Milan Italy
Show AbstractTo overcome the high cost of the catalyst in Direct Methanol Fuel Cell (DMFC) technology, research is moving towards the reduction in the Pt loading in the electrodes by increasing the electrochemical surface area. To date, the state of the art of catalyst supports is dominated by mesoporous carbon: it shows high conductivity but suffer from stability issues especially at high potential (i.e. at the cathode side) and over long periods of operation.
As shown in the literature, titanium nitride (TiN) has a metal-like conductivity with an outstanding chemical stability [1] due to the surface passivation during the operation. This could be useful to mitigate the corrosion of the electrode and to preserve the structure of the platinum catalyst from ripening. Moreover, it is also reported to be functional towards the oxidation of adsorbate CO on platinum active sites [2] so it can be suitable also for application in the anodic compartment.
In this contribution, we report about Pt-TiN with low metal loading (as high as 0.3 mg/cm2) catalysts support with self-assembled, hierarchical mesoporous nanostructure, grown by Pulsed Laser Deposition. This non conventional approach controls the gas dynamics of a nanoclusters-inseminated supersonic jet in order to differentiate the resulting impaction deposition, affecting the growth of the film. We demonstrate that it is possible to obtain a catalyst support with large surface area whose morphology can be controlled at the nanoscale. Such as a support could be ideal for the highest platinum utilization, and also for the metal loading reduction, since it has similar effects with respect to the metallic Ru in commercial DMFC catalysts with a much lower cost.
Electrochemical and physical characterization are performed, showing performances towards both methanol oxidation and oxygen reduction, and revealing information about the interaction between catalyst, scaffold and reactants to characterize stability, catalytic activity and CO tolerance.
These results show the potential of a PVD based technique that opens the doors of the nanoscale to the fabrication of high performing electrodes whose morphological and electrical properties are easily tuned. This approach holds promises for a consistent reduction in the metal loading in DMFC technology.
[1] M. Wittmer, B.Studer and H.Melchior, Journal of Applied Physics, 52, 5722 (1981)
[2] M. Roca-Ayats, G. Garcia, J.L. Galante, M.A. Peña and M.V. Martinez-Huerta, Journal of Physical Chemistry C 117, 20769-20777 (2013)
8:00 PM - NM05.07.35
Localized Spot-by-Spot High Dose MeV Ion Implantation into Silica
John Demaree 1 , Daryush Ila 2
1 Weapons & Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States, 2 Department of Chemistry and Physics, Fayetteville State University, Fayetteville, North Carolina, United States
Show AbstractIn this work we have studied the change in the optical properties of Infrasil (Heraeus high-purity optical quality fused quartz silica) before and after spot-by-spot implantation of 0.785 MeV Ag and 1.450 MeV Au ions using a National Electrostatics 5SDH-2 tandem accelerator. The ion beams were focused to spots roughly 2mm in diameter, and after a given fluence was delivered, the substrate was moved stepwise in horizontal and vertical directions in 0.5mm increments across an area approximately 8mm x 8mm. The fluence delivered in each overlapping spot was calculated to produce uniform total implantation doses of Au, Ag, and (sequentially) Au + Ag ranging from 1016 /cm2 to 1017 /cm2. The effects of this high dose spot-by-spot method were then compared with traditional raster scan implantations, in which the beam is swept over the entire area quickly, and the entire area is implanted uniformly over time.
The implanted area, several millimeters by several millimeters across, was studied before and after annealing using optical absorption photo spectrometry to assess the optical change in the material and evidence of Au and Ag nanocluster formation. Rutherford Backscattering Spectrometry (RBS) was used to confirm the implantation dose and the uniformity of the implanted area. We have observed, specifically in spot-by-spot Au implanted silica, evidence of a quadrupole interaction which produces a widening of the Au nanocluster absorption band beyond 530nm, and which has been seen in past studies using traditional raster scanning implantation only when followed by high temperature annealing.
In this presentation we will compare the results obtained for both spot-by-spot implantation of Au and Ag into Infrasil with past raster scan implantations, and comment on the effect of this method on nanocluster formation and growth, as well as possible changes in the surface topography of this glassy material.
8:00 PM - NM05.07.36
High Volume Fraction Nanocrystal Production by Ion Beam and Applications
Daryush Ila 1
1 , Fayetteville State University, Fayetteville, North Carolina, United States
Show AbstractVarious research groups have tried to control the size, shape, distribution, and concentration of nanocrystals on and inside silica substrate with ion beams for decades. In the past two decades, ion beam users have mastered controlling the size, shape and, somehow, the distribution of nanocrystals by combining the implantation and co-deposition, sometimes followed by post-MeV ion irradiation.
We have developed a process [1], which has been presented in a series of research work initiated during the past decade, to produce a high volume fraction of mono and bi-element nanocrystals in order to effectuate the creation of pseudo-quantum dot lattices. Theoretically, A. Balandin and O. Lazarenkova have shown the enhancement of the thermoelectric figure-of-merit in regimented quantum dot super lattices which require high volume fraction. We will report on our in-house developed process using simple systems of metals such as gold and/or silver in silica (SiO2). This process takes advantage of two techniques: 1) Ion Beam Assisted Deposition, using an argon beam, and 2) post-bombardment by a 5 MeV Si ion beam. Using these two methods, we produced highly dense nanocrystals of Au and/or Ag in SiO2 in which the interactions between these nanocrystals resulted in increased electrical conductivity, reduced thermal conductivity, and an increase in the square of the Seebeck coefficient, thereby increasing the figure of merit. Producing a thermoelectric material with a high figure of merit means that we produced a highly efficient thermoelectric material that operates at room temperatures and at temperatures as high as 973K [2, 3], as indicated by our measurements. In this lecture we will review the results over past decades and present our most recent findings. We will describe the in-house process that we developed, which resulted in the production of thermally high insulating but electrically high conductive materials with high Seebeck coefficients.
1. D. ILA, Method for production of high figure of merit TEM materials, USPTO No. US 9,537,077 B2 (Jan. 3, 2017)
2. D. ILA, High eff. TEM Dev., USPTO No. US 8841539 B2 (Sept. 23, 2014)
3. D. ILA, Appl. Surf. Sc. Vol. 310, 217 (2014)
Symposium Organizers
David Horwat, Institut Jean Lamour-University de Lorraine
R. Mark Bradley, Colorado State University
Ulf Helmersson, Linköping Universitet
François Reniers, Université Libre de Bruxelles
NM05.08: Plasmas for Carbon-Based Materials
Session Chairs
Tzahi Cohen-Karni
Raul Gago
Thursday AM, November 30, 2017
Hynes, Level 3, Room 313
8:30 AM - NM05.08.01
“Synthesis-on” and “Synthesis-off” Modes of Carbon Arc Operation During Synthesis of Carbon Nanotubes
Rachel Selinsky 1 , Shurik Yatom 2 , Bruce Koel 1 , Y Raitses 2
1 , Princeton University, Princeton, New Jersey, United States, 2 , Princeton Plasma Physics Laboratory, Princeton, New Jersey, United States
Show AbstractArc discharge synthesis of single-walled carbon nanotubes (SWCNTs) remains largely uncontrollable, due notably to incomplete understanding of the synthetic process itself. We show that synthesis of SWCNTs by carbon arc is not a continuous process, but instead consists of two distinct modes, one of which produces the majority of the nanomaterials and during which proportionally more carbon nanotubes are collected. The two modes, “synthesis-on” and “synthesis-off,” were characterized for a typical arc configuration, a hollow anode filled with a mixture of powdered metal catalysts and graphite, using in situ electrical, imaging, and spectroscopic diagnostics and ex situ imaging and spectroscopy. The synthesis-on mode duration is rare as compared to total arc run-time, helping to explain the poor selectivity of the final product, a known inadequacy of arc synthesis.
8:45 AM - NM05.08.02
High-Current Field Emission from “Flower-Like” Graphene Flakes Grown on Tip of Nichrome (8020) Wire
Xiaolu Yan 1 , Guoan Cheng 1 , Ruiting Zheng 1 , Xiaoling Wu 1
1 , Laboratory of Nanomaterial and Technology, College of Nuclear Science and Technology, Beijing Normal University, Beijing China
Show AbstractThe desirable properties of graphene, such as excellent electrical conductivity, chemical stability, high aspect ratio (the ratio of lateral size to thickness), and good mechanical properties, qualified it an attractive candidate for field emission cathode. The presence of abundant sharp edges may render graphene superior for electron tunneling, and display good field-emission properties with low threshold field, large field-enhancement factor, and good emission stability. But majority of common deposition methods lead to graphene sheets lay flat on the substrate surface, limiting the applications of the atomically thin edges of graphene. To take advantage of the high field enhancement, graphene sheets should have a considerable quantity and stand on their edges.
In this work, we synthesized the graphene flakes on tip of nichrome (8020) wire (Diameter 80 µm) by microwave plasma enhanced chemical vapor deposition (PECVD) with gas mixtures of acetylene and hydrogen, in the absence of else catalyst. These resultant random arrays of free-standing few-layer grapheme flakes are aligned vertically to the substrate surface in a high-density and stacked to each other to form several larger “flower-like” agglomerates in spherical shapes. The graphene flakes grown on tip of nichrome (8020) wire is found to be a good field electron emitter. The FE performance of the graphene flakes emitter shows a low threshold field of 0.55 V/µm, a large field enhancement factor of 9455±460 (assuming a work function of 4.64 eV), a large field emission current density of 22.18 A/cm2 at a relatively low electric field of 2.70 V/µm, and an excellent field emission stability at high emission current densities (6.93 A/cm2). Graphene flakes emitter fabricated by microwave PECVD has a uniform morphology and high graphene density, ensures emission uniformity and sufficient effective field-emission tips. The good adhesion and contact between graphene nanoflakes and the nichrome (8020) wire substrate facilitates electron transport, and consequently improves the field emission performance in some way. Indeed, this graphene flakes behaved better than most of the previously-reported FE studies of graphene-based materials. It can be used in variety of applications that include cathode-ray tube monitors, X-ray sources, electron microscopes, high energy accelerators and other vacuum electronic applications
9:00 AM - *NM05.08.03
Nanowire-Mesh Templated Growth of Out-of-Plane Three-Dimensional Fuzzy Graphene
Raghav Garg 2 , Sahil Rastogi 2 , Michael Lamparski 1 , Sergio de la Barrera 4 , Gordon Pace 2 , Noel Nuhfer 3 , Benjamin Hunt 4 , Vincent Meunier 1 , Tzahi Cohen-Karni 3 2
2 Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 1 Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States, 4 Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 3 Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractGraphene, a honeycomb sp2 hybridized carbon lattice, is a promising building block for hybrid-nanomaterials due to its electrical, mechanical, and optical properties. Graphene can be readily obtained through mechanical exfoliation, solution-based deposition of reduced graphene oxide (rGO), and chemical vapor deposition (CVD). The resulting graphene films’ topology is two-dimensional (2D) surface. Recently, synthesis of three-dimensional (3D) graphitic networks supported or templated by nanoparticles, foams, and hydrogels was reported. However, the resulting graphene films lay flat on the surface, exposing 2D surface topology. Out-of-plane grown carbon nanostructures, such as vertically aligned graphene sheets (VAGS) and vertical carbon nanowalls (CNWs), are still tethered to 2D surface. 3D morphology of out-of-plane growth of graphene hybrid-nanomaterials which leverages graphene's outstanding surface-to-volume ratio has not been achieved to date.
Here we demonstrate highly controlled plasma enhanced CVD (PECVD) synthesis of 3D out-of-plane single- to few-layer fuzzy graphene (3DFG) on a Si nanowire (SiNW) mesh template. By varying graphene growth conditions (CH4 partial pressure and process time), we control the size, density, and electrical properties of the NW templated 3DFG (NT-3DFG). 3DFG growth can be described by a diffusion-limited-aggregation (DLA) model. The porous NT-3DFG meshes exhibited high electrical conductivity of ca. 2350 S m-1. NT-3DFG demonstrated exceptional electrochemical functionality, with calculated specific electrochemical surface area as high as ca. 1017 m2 g-1 for a ca. 7 μm thick mesh. This flexible synthesis will inspire formation of complex hybrid-nanomaterials with tailored optical and electrical properties to be used in future applications such as sensing, and energy conversion and storage.
Reference - R. Garg, S.K. Rastogi, M. Lamparski, S. de la Barrera, G.T. Pace, N.T. Nuhfer, B.M. Hunt, V. Meunier, T. Cohen-Karni, “Nanowire-Mesh Templated Growth of Out-of-Plane Three-Dimensional Fuzzy Graphene“. ACS Nano. (2017), DOI: 10.1021/acsnano.7b02612
9:30 AM - NM05.08.04
Vertically-Aligned Conical Tree-Like Carbon Nanostructures Grown by ECR-PECVD for Application as Anode of Lithium-Ion Battery
Monalisa Ghosh 1 , Venkatesh Gopal 1 , G. Mohan Rao 1
1 , Indian Institute of Science, Bangalore India
Show AbstractBranched conical tree-like carbon nanostructures are grown by plasma enhanced chemical vapour deposition (PECVD) using electron cyclotron resonance (ECR) plasma system. These nanostructures have a nanotube aligned perpendicular to the surface of the substrate with carbon films branching from the central tube giving it a conical tree like appearance. These films have a high exposed surface area and thus can act as a three dimensional (3D) anode for lithium ion battery.
The nanostructures are grown in a custom made ECR system with a microwave power of 500W using acetylene and hydrogen in 2:1 ratio, at a working pressure of 7x10-4 mbar in the presence of a negative substrate bias of 200V. Thin films of these nanostructures are deposited on a seed layer of Nickel of about 10 nm in thickness, which is grown by DC sputtering. The as grown films are characterised by field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) to understand the morphological features and chemical nature of the films. From the electron microscopy, we came to understand the growth pattern and nature of the nanostructures, while the XPS confirmed the chemical composition to be pure carbon. EDAX from TEM showed the presence of Ni nanoparticle at the tip of the central tube of the nanostructure but not on the carbon branches. Raman spectroscopy confirmed the graphitic nature of the material.
The electrochemical performance of the material as an anode of lithium ion battery has been studied by depositing the material on circular copper substrates of thickness 0.25 mm. Swagelok type half-cells are assembled with lithium metal foil as the reference and counter electrode. LiPF6 salt dissolved of ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) is used as the electrolyte with absorbed glass mat (AGM) of thickness 3 mm acting as separator. Lithiation capacity for the first cycle is 328 µAhr cm-2 µm-1 and thereafter it has decreased up to 102 µAhr cm-2 µm-1 after 5 th cycle. Delithiation capacity for the first cycle is 118 µAhr cm-2 µm-1 (1232 mAhr g-1), whereas, after fifth cycle it is 100 µAhr cm-2 µm-1(1044 mAhr g-1). After initial loss in the specific capacity, it remains fairly constant. The cyclic voltammetry study shows typical pattern for carbon material and indicates repeatability in performance of the material as anode of lithium ion battery. The delithiation capacity of this nanostructured carbon material is comparable to that of benchmark value of 1000 mAhr g-1 for CNT anodes and much higher than that of other commonly used carbonaceous anode materials [1-2]
References:
[1] N. Mahmood, T.Tang, Y. Hou, Adv. Energy Mater. 2016, 1600374
[2] S. Goriparti, E. Miele, F De Angelis, E. Di Fabrizio, R. Zaccaria , Claudio Capiglia Journal of Power Sources, 2014, 257, 421-443
9:45 AM - NM05.08.05
All Gas-Phase Synthesis of Free-Standing Graphene Nanosheets in a Microwave Plasma Reactor
Adrian Munzer 1 , Christof Schulz 1 2 , Hartmut Wiggers 1 2
1 , University of Duisburg-Essen, Duisburg Germany, 2 , CENIDE, Duisburg Germany
Show AbstractSince the first isolation of graphene in 2004, the research on this novel material has increased intensively. Many groups are focusing on the development of facile and scalable synthesis routes for high-quality and high-performance graphene. Due to its unique electrical, mechanical and thermal properties, graphene is regarded as a potential material for many fields of energy-related applications such as energy conversion and storage with electrocatalysts, supercapacitors, and lithium ion batteries. So far, the commercial application of graphene is hindered by expensive and time-consuming synthesis techniques, e.g., growth on sacrificial substrates by epitaxy and chemical vapor deposition (CVD), or complex chemical process technology starting from graphite.
In this paper, we present a facile synthesis method for preparing free-standing few-layer-graphene (FLG) by gas-phase reaction, which is carried out in a plasma reactor using simple alcohol vapor (e.g. ethanol, isopropanol, butanol) as precursor. This scalable synthesis route can produce high-purity FLG with production rates up to 1 g/h.
The prepared FLG was characterized by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, 4-point measurements, and TEM in combination with EELS. The results indicate that the properties of the analyzed material are at least comparable and even better in quality (measured by Raman spectroscopy) and performance than graphene produced by established chemical procedures, e.g. Hummers’ method. The specific surface area is in the range of a few hundred m2/g. In particular, XPS and FTIR results show that the synthesized graphene is of very high purity with very low impurities and an oxygen content of less than 1 at%. This leads to very high electrical conductivity, even of simple pressed pellets, as could be verified with electrical 4-point measurements. A couple of tests utilizing our graphene for lithium ion batteries and electrocatalysis will be shown.
10:30 AM - NM05.08.06
Simple Synthesis of Patterned Graphene Oxide from PECVD Grown Graphene via Laser Annealing
Taesung Jung 1 , Hyungsik Kim 1 , Insung Choi 1 , Young Kim 1 , Rizwan Huq 1 , Sahng-Kyoon Jerng 2 , Seung-Hyun Chun 2 , James Hone 1 , James Im 1 , Ken Shepard 1
1 , Columbia University, New York, New York, United States, 2 , Sejong University, Seoul Korea (the Republic of)
Show AbstractGraphene oxide (GO) is a graphene film interspersed with oxygen-containing functionalities. The mixture of sp2- and sp3-hybridized carbon and chemical reactivity of oxygen sites give GO its unique electrical, optical, and electrochemical properties, which have recently led to wide exploration of GO-based applications such as batteries, sensors, and bio-interfaces. Despite such efforts, there remains no simple, reliable method to assemble GO on an arbitrary substrate. Current methods of GO preparation require dispersion and exfoliation of graphite oxide in a solvent, from which GO flakes are transferred onto the substrate. Such approaches often involve complex transfer steps, suffer from non-uniform assembly, and are difficult to precisely align.
Here, we report a novel method that enables uniform, geometrically well-defined preparation of GO using an excimer laser (XeCl 308nm) while avoiding any wet processing. PECVD grown multi-layered graphene, which can be directly deposited onto any arbitrary substrate, was annealed with the excimer laser in an ambient environment to produce selectively patterned GO. Raman spectroscopy confirmed the formation of GO whose oxidation peak levels were tunable through laser intensity. Furthermore, electrical carrier transport in GO was shown to be affected by laser fluence. In conclusion, our excimer laser-based synthesis using PECVD graphene paves the way for utilizing GO in large-scale integrated devices.
10:45 AM - NM05.08.07
Nitrogen-Doped sp2/sp3 Hybrid Carbon Films for Electrocatalytic Reduction of Carbon Dioxide
Namal Wanninayake 1 , Sidney Herrell 1 , Ruixin Zhou 1 , Marcelo Guzman 1 , Doo Young Kim 1
1 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractCarbon dioxide (CO2) is a major greenhouse gas which contributes to the global warming. Thus it is important to suppress the level of CO2 by either sequestration or conversion to valuable products. Recently, electrochemical conversion of CO2 driven by intermittent renewable energy has emerged as an economically viable route. Several studies have shown that nitrogen-doped carbon is a metal-free, cost-effective electrocatalyst for the reduction of CO2. Nitrogen-doped carbon-based materials possess high electrical conductivity and a low activation barrier for electrochemical CO2 reduction reaction (CO2RR). However, the catalytic mechanism of nitrogen species and the role of sp2/sp3 carbon moiety in the electrochemical reduction are still ambiguous. In this work, nitrogen-doped carbon films with the controlled contents of sp2/sp3 carbons were prepared by a microwave-assisted chemical vapor deposition technique, and the electrocatalytic activities of the grown films were investigated in aqueous electrolyte. Morphology, microstructure, and chemical states of nitrogen-doped electrocatalysts were characterized by scanning electron microscopy, transmission electron microscopy, Wide-angle X-ray diffraction, and X-ray photoelectron spectroscopy. Electrochemical tests were performed with a home-built electrochemical cell. Gaseous and liquid products from CO2RR were assessed by gas chromatography and nuclear magnetic resonance spectroscopy. Carbon monoxide(CO), and methane(CH4) gases were noted as the main products of CO2RR. Our results indicate that pyridinic nitrogen sites in carbon films promote the catalytic reduction of CO2 by the adsorption of reaction intermediates. Furthermore, the ratio of sp2/sp3 carbon significantly influenced the onset potential for the generation of CO and hydrogen (H2). Nitrogen-doped catalyst with larger sp2 carbon content achieved the production of CO with nearly 60% faradaic efficiency at -1.20 V vs. RHE, while with larger sp3 carbon content, H2 evolution reaction was dominant at all applied potentials. These results indicate that a synergistic interaction between sp2 carbon and nitrogen-related catalytic sites enhances the selectivity of CO2RR. Understanding of a mechanism and active sites made from nitrogen dopants and sp2/sp3-carbon species will provide invaluable insights for the development of efficient and robust, metal-free carbon catalysts for CO2RR.
11:00 AM - NM05.08.08
Hybrid Nanocomposites of Nanostructured Co3O4 Interfaced with Reduced/Nitrogen-Doped Graphene Oxides for Selective Improvements in Electrocatalytic and/or Supercapacitive Properties
Sheng Hu 1 , Bamin Khomami 1 , Dibyendu Mukherjee 1 , Erick Ribeiro 1
1 , University of Tennessee, Knoxville, Knoxville, Tennessee, United States
Show AbstractPerformance enhancements in next-generation electrochemical energy storage/conversion devices require the design of new classes of nanomaterials that exhibit unique electrocatalytic and supercapacitive properties. To this end, we report the use of a facile and green technique laser ablation synthesis in solution (LASiS) operated with cobalt as the target in graphene oxide (GO) solution in tandem with two different post-treatments to manufacture three kinds of hybrid nanocomposites (HNCs) namely, 1) Co3O4 nanoparticle (NP)/reduced graphene oxide (rGO), 2) Co3O4 nanorod (NR)/rGO, and 3) Co3O4 NP/nitrogen-doped graphene oxide (NGO). The laser-induced plasma plume produces seeding Co NPs with opposite surface charges to GO that electrostatically attracts the two species to form HNCs. FTIR and Raman spectroscopic studies indicate that both chemical and charge-driven interactions are partially responsible for embedding the Co3O4 NPs/NRs into the various GO films. We tune the selective functionalities of the as-synthesized HNCs as oxygen reduction reaction (ORR) catalysts and/or supercapacitors by tailoring their structure-property relations. Specifically, the nitrogen doping in the NP/NGO HNC samples promotes higher electron conductivity while hindering aggregation between 0D CoO NPs that are partially reshaped into Co3O4 nanocubes due to induced surface strain energies. Our results indicate that such interfacial energetics and arrangements lead to superior ORR electrocatalytic activities. On the other hand, the interconnecting 1D nanostructures in the NR/rGO HNCs benefit charge transport and electrolyte diffusion at the electrode-electrolyte interfaces, thereby promoting their supercapacitive properties. The NP/rGO HNCs exhibit intermediate functionalities towards both ORR catalysis and supercapacitance.
11:15 AM - NM05.08.09
Thermal Plasma Synthesis of Carbon Coated Magnesium for Energy Storage
Burak Aktekin 1 , Cavit Eyövge 1 , Tayfur Ozturk 1
1 Department of Metallurgical and Materials Engineering, ENDAM Center for Energy Storage Materials and Devices , Middle East Technical University, Ankara Turkey
Show AbstractMagnesium is a material of considerable interest for electrochemical as well as thermal energy storage. Electrochemically, Mg bearing alloys are already in use in NiMH batteries and there is a considerable interest in the developing Mg or Mg rich alloys for the same purpose. In a separate line, Mg is in the center of recent efforts to develop Mg-ion batteries. Carbon coated magnesium or magnesium nanopartciles emebedded in a graphitic matrix are quite relevant to all these and could provide solutions to some of the problems currently faced in the respective batteries. The interest in Mg-C composites has a different root in thermal energy storage. In heat storage tanks, MgH2 is often mixed with graphite so as to improve the thermal conductivity. It also helps stabilize the hydride beds by isolating Mg particles which would otherwise sinter together resulting in the loss of storage capacity.
The current study was undertaken to develop Mg-C composites at a variety of scales. The synthesis was achieved by co-feeding magnesium and methane into an RF thermal plasma reactor. This yielded carbonaceous material with magnesium particles 5-10 nm in size embedded in graphitic matrix. A further reduction down to 2-3 nm was possible but required reductions in the precursor feed rate. It was found that 2 wt.% carbon was sufficient to fully protect magnesium particles of approx. 260 nm in size. Light milling, however, disrupts the continuity of graphitic envelop and the particles then react both with oxygen and hydrogen. The potential of carbon coated magnesium as electrodes in rechargeable batteries are discussed.
11:30 AM - NM05.08.10
Microwave Plasma Chemical Vapor Synthesis of Nano-Crystalline Diamond Powder
Hideo Isshiki 1 , Ryota Yamada 1
1 , University of Electro-Communications, Tokyo Japan
Show Abstract
Diamond has excellent characteristics such as high hardness, high thermal conductivity and wide band gap. Recently color centers in nano-crystalline diamond (NCD), such as nitrogen-vacancy (N-V) centers, are attracting much attention to apply to fluorescent biomarkers and single photon emitters. Detonation method is a powerful method to produce NCD powder for the mass production. However the quality control is difficult during its detonation process, and it takes many post-processes to qualify the products as NCD. We have discovered the diamond nucleation enhancement by atomic silicon micro addition during bias-enhanced nucleation (BEN) process predicting diamond growth [Jpn. J. Appl. Phys. 51 (2012) 090108]. Surface-enhanced Raman scattering spectrum of the nuclei shows quite similar to the typical spectrum of NCD. It can be considered that the added silicon atom functions as a nucleation center. In this report, a novel approach to synthesize fluorescent nano-crystalline diamond (NCD) is proposed. Isolated NCD particles are generated in methyl/hydrogen plasma into which atomic silicon is additionally introduced as the diamond nucleation center. This mechanism is just like snow crystals arising from the cloud.
Chemical vapor synthesis (CVS) of NCD was performed using a microwave plasma torch. The nucleation processes were performed in the microwave plasma using hydrogen diluted Tetra-methyl silane (TMS: Si(CH3)4), and the reactor pressure was 4kPa. TMS was decomposed into methyl radical and atomic silicon in hydrogen plasma, and the atomic silicon preserving sp3 bonds floats in the plasma as the diamond nucleation center. Methyl radicals are attached to the silicon atom one after another, resulting in formation of diamond nuclei. NCD can grow only during a residual time in the plasma. In the CVS system, NCD were efficiently collected from the reactant downstream by a remote anode cup. NCD with a grain size of 30-50nm were collected. Note that any NCD did not obtained from methyl/hydrogen plasma without atomic Si. Raman spectra exhibits disappearance of G-band indicating existence of graphite, appearance of tetrahedral amorphous carbon and narrowing of D-band.
We consider that the grain size can be changed by residual time in the plasma owing to the gas flow rate. It is expected that MP-CVS is a good way to fabricate the high quality NCD powder.