Symposium Organizers
JoseLuis Endrino Instituto de Ciencia de Materiales de Madrid
Andre Anders Lawrence Berkeley National Laboratory
Joakim Andersson Uppsala University
David Horwat Institut Jean Lamour
Mykola Vinnichenko Institute of Ion Beam Physics and Materials Research
Symposium Support
Acree Technologies Inc
Asociacion de la Industria Navarra
Impact Coatings AB
Metal Estalki S.L.
Sandvik AB
S1: Advanced, Reactive and Pulsed Sputtering
Session Chairs
Joakim Andersson
Jose Endrino
Tuesday PM, April 26, 2011
Room 3004 (Moscone West)
9:15 AM - S1: SPUT
Symposium Welcome - Brief Overview of the Symposium by the Organizers
Show Abstract9:30 AM - S1.1
Comparison of Transport Properties in Pulsed DC Magnetron and Ion Beam Sputtered Vanadium Oxide Thin Films Used as Imaging Layers in Infrared Microbolometers.
Bharadwaja Srowthi 1 , S. Kozlowski 3 , H. Basantani 3 , Myung-Yoon Lee 2 , Jing Li 1 , S. Ashok 3 , T. Jackson 2 , M. Horn 3 , Sami Antrazi 4
1 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Electrical Engineering Department, The Pennsylvania State University, University Park, Pennsylvania, United States, 4 , 4Wave Inc., Sterling, Virginia, United States
Show AbstractThere has been a continuous effort over the last two decades to develop smaller and better performing uncooled microbolometers in order to reduce both weight and power in highly specialized thermal imaging applications such as night vision and scanning thermal microscopy. In order to operate effectively, microbolometers must have a high temperature coefficient of resistance (TCR) and low noise characteristics. In addition, the materials used to manufacture microbolometers must be inexpensive and compatible with current complementary metal oxide semiconductor (CMOS) processes. One of the material choices for microbolometer focal plane arrays is mixed vanadium oxide (VOx) thin films with a TCR range between -2 % per K and -3 % per K at room temperature. Currently most manufacturers of commercial and military thermal imaging cameras use ion beam sputter deposited VOx films as the imaging layer for their uncooled focal plane arrays. In this presentation, we will discuss the conduction mechanisms for VOx thin films with different microstructures and having similar room temperature resistivity values. These films have been prepared using pulsed DC reactive magnetron sputtering and ion beam sputtering of a vanadium target under various processing conditions. Processing parameters such as operating partial pressure, reactive gas ratio, substrate bias conditions were varied to optimize the microstructure and electrical performance of the resultant VOx thin films. By varying the reactive gas composition (Ar:O), the VOx films microstructure was varied from rocksalt fcc VO nanocrystallites embedded in an amorphous matrix to complete amorphous state. With an rf substrate bias assisted pulse dc sputtering, VOx films of columnar microstructure having micro-twins were obtained. By varying the reactive pulsed dc sputtering conditions, the resistivity of VOx films varied between 1 mΩcm to 60 kΩcm with corresponding TCR between 0 to - 4% per K. For comparison, ion beam sputter deposited films were also evaluated in the 0.05 to 5Ωcm range. Two types of conduction mechanisms were found to dominate in the measured temperature range (10-300K), namely band conduction through extended states (that dominates at the intermediate temperature region) and hopping around the Fermi level (that dominates at the low-temperature region). At low temperature, the density of states and other related hopping parameters near the Fermi level were correlated with the film microstructure. Furthermore, the low frequency electrical noise (1/f-noise) due to conductivity fluctuations in these VOx films was analyzed within the framework of Hooge-Vandamme relation. These properties were correlated to both the film microstructure and the deposition process and conditions.Acknowledgements: This work is financially supported by the U.S. Army Research Office and U. S. Army Research Laboratory under Cooperative Agreement # W911NF-0_2-0026.
9:45 AM - S1.2
Thick Beryllium Coatings by Magnetron Sputtering.
Hongwei Xu 1 , Abbas Nikroo 1 , Kelly Youngblood 1 , Kari Morena 1 , Dan Wu 1 , Tim Fuller 1 , Craig Alford 2 , Jeff Hayes 2 , Andy Detor 2 , Morris Wang 2 , Alex Hamza 2 , Tony Buuren 2 , Eric Chason 3
1 , General Atomics, San Diego, California, United States, 2 , Lawrence Livermore National Laboratory, Livermore, California, United States, 3 , Brown University, Providence, Rhode Island, United States
Show AbstractThick (>150 μm) beryllium coatings are studied as an ablator material of interest for fusion fuel capsules for the National Ignition Facility (NIF). As an added complication, the coatings are deposited on mm-scale spherical substrates, as opposed to flats. DC magnetron sputtering is used because of the relative controllability of the processing temperature and energy of the deposits. We used ultra small angle x-ray spectroscopy (USAXS) to characterize the void fraction and distribution along the spherical surface. We investigated the void structure using a combination focused ion beam (FIB) and scanning electron microscope (SEM), along with transmission electron microscopy (TEM), the details of which will be presented. Our results show a few volume percent of voids and a typical void diameter of less than two hundred nanometers. Understanding how the stresses in the deposited material develop with thickness is important so that we can minimize film cracking and delamination. To that end, an in-situ multiple optical beam stress sensor (MOS) was used to measure the stress behavior of thick Beryllium coatings on flat substrates as the material was being deposited. We will show how the film stress saturates with thickness and changes with pressure. This work was supported by U.S. DOE under contract DE-AC52-06NA27279.
10:00 AM - S1.3
Chemistry and Physical Properties of Gold Incorporated Zirconium Oxide.
David Horwat 1 , Thomas Gries 1 , José Luis Endrino 2
1 , Institut Jean Lamour, Nancy France, 2 , ICMM-CSIC, Madrid Spain
Show AbstractGold is known as an inert material. It is usually admitted as the most noble metal. Nevertheless, the hydrothermal synthesis of auric oxide Au2O3 has been reported and its electronic structure investigated by means of X-ray absorption near edge structure (XANES) [1]. Unfortunately Au2O3 presents a positive enthalpy of formation and exhibits a fast decomposition kinetic in normal conditions. Plasma methods may be of relevance to force auric oxide to form. To date there is no clear evidence of the formation of Auric oxide in thin films form. The present contribution reports on the thermal evolution and properties of gold incorporated yttria stabilized zirconia (YSZ) thin films deposited by magnetron co-sputtering. The formation of gold nanoparticles is evidenced by X-ray diffraction and transmission electron microscopy. The chemistry of the gold particles is probed by XANES. It is observed that the very fine gold nanoparticles retain a small size even after annealing at 600 °C in air. The matrix experiences crystallization to YSZ accompanied by a slight modification of the particle chemistry. The electronic structure shows that auric oxide is formed. The synthesized nanocomposite structure exhibit a potential interest for optical, catalytic and electronic applications.[1] N. Weiher, E. A. Willneff, C. Figulla-Kroschel, M. Jansen, S. L. M. Schroeder, Solid State Communications 125 (2003) 317
10:15 AM - S1.4
Synthesis by Magnetron Sputtering and Functionalization by Laser Interference Irradiation of Noble Metal Oxide Thin Films.
Rodolphe Catrin 1 , David Horwat 2 , Thomas Gries 2 , Sylvie Migot 2 , Jean-Francois Pierson 2 , Christoph Pauly 1 , Yi Hu 3 , Frank Muecklich 1
1 Materials Science and Engineering, Saarland University, Saarbrücken, Saarland, Germany, 2 CP2S, UMR 7198 CNRS-Nancy-Universite-UPV-Metz, Institut Jean Lamour, Nancy France, 3 , Paul Scherrer Institute, Villingen Switzerland
Show AbstractNoble metal oxide thin films offer outstanding possibilities for generating novel microstructures and properties owing to their rich chemistry. Magnetron sputtering is an efficient method to synthesize noble metal oxides. This results from the out of equilibrium conditions owing to the condensation process. Laser interference irradiation, also known as “laser interference metallurgy”, can be used to induce a local heat treatment of materials. By splitting the primary laser beam of an high power pulse nanosecond Nd:YAG laser working at 355 nm and focusing the two interfering beams on the sample surface, a line-like pattern of 20 µm period resulting in a sinusoid profile could be achieved. It allows a precise redesigning of surface and in-depth microstructures in terms of local and periodic heating at the interference maxima positions.We first describe the parameters that allow the synthesis of noble metal oxide thin films in the Pd-Pt-O, Ag-Cu-O and Au-Zr-Y-O systems. This is followed by a detailed analysis of the decomposition processes triggered by the local thermal treatment applied by laser interference irradiation. A partial decomposition is observed, which results in the segregation of noble metal nanoparticles at the origin of a locally tailored resistivity and the development of Surface Plasmon Resonance (SPR). The decomposition has been investigated by X-ray diffraction, white light interference microscopy, Energy Dispersive X-ray Spectrometry (EDS), Secondary Ion Mass Spectrometry (SIMS), scanning and transmission electron microscopies. Optical properties and room temperature electrical resistivity were evaluated using spectrophotometry and four-point probe method, respectively.
10:30 AM - **S1.5
Phase and Morphological Evolution of Heterogeneous TiO2 Films Produced by Reactive Pulsed Magnetron Sputtering.
Raul Gago-Fernandez 1 , Andres Redondo-Cubero 2 4 , Zsolt Czigany 3 , Luis Vazquez 1
1 , Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Madrid Spain, 2 , Instituto de Sistemas Optoelectrónicos y Microtecnología, Universidad Politecnica de Madrid, Madrid Spain, 4 ISOM and DIE, E.T.S.I. Telecomunicacion, Universidad Politecnica de Madrid, Madrid Spain, 3 , Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, Budapest Hungary
Show AbstractThe versatile properties displayed by different structural phases of TiO2 have triggered the interest in tuning the atomic arrangements and understanding the growth mechanisms that promote the desired phase. In thin solid film form, TiO2 normally grows with single or mixed anatase and rutile phases, as well as amorphous [1]. In this work, heterogeneous TiO2 thin films consisting of a mixture of amorphous and nanocrystalline rutile phases have been grown by reactive pulsed magnetron sputtering under different O2 partial pressures in an O2/Ar atmosphere [2]. Special attention has been paid to the phase evolution with growth time, where relevant structural information has been extracted from the combination of spectroscopic ellipsometry (SE), X-ray absorption near-edge structure (XANES) and transmission electron microscopy (TEM) analysis. Interestingly, the evolution of the heterogeneous phase mixture leads to a correlation between the surface morphology, as imaged by atomic force microscopy (AFM), and the underlying phase on the surface. The morphological evolution is determined by the nucleation rate of rutile and the different growth rates of each phase. In this way, a (nanoscale) lateral phase heterogeneity is also present at the surface. Thermal studies involving growth at different substrate temperatures and post-deposition annealing experiments have also been carried out to address further control on the phase formation and stability. REFs: [1] M. D. Wiggins, M. C. Nelson, C. R. Aita, J. Vac. Sci. Technol. A 1996, 14, 772; [2] R. Gago, M. Vinnichenko, A. Redondo-Cubero, Zs. Czigány, and L. Vázquez, Plasma Processes and Polymers 7, 813 (2010).
11:30 AM - S1.6
RF Power Driven Lattice Dynamics Behavior of Al-doped ZnO Thin Films.
Bhaskar Mohanty 1 , Byeong-Kon Kim 1 , Yeon-Hwa Jo 1 , Deuk-Ho Yeon 1 , Ik-Jin Choi 1 , Yong Soo Cho 1
1 Materials Science & Engineering, Yonsei University, Seoul Korea (the Republic of)
Show AbstractThe influence of discharge power on lattice dynamic behavior of Al-doped ZnO (ZnO:Al) thin films has been investigated. The films have been grown by RF magnetron sputtering of a ZnO:Al (2 wt %) compound target at various RF powers in the range of 50 to 200 W in pure Ar ambient (2 mtorr) at room temperature. XRD measurements show that deposition at 50 W yields highly c-axis oriented films of hexagonal-wurtzite structure characterized by intense (002) and (004) Bragg reflexes. With further increase in RF power components with other orientations are observed, which indicates that a higher RF power interrupts stable grain growth leading to random orientation of the crystallites in contrast to the expected strong c-axis orientation. Lattice dynamic behavior has been studied by room temperature micro-Raman measurements in backscattering geometry. A comparison of the Raman spectra of the ZnO:Al films with an undoped ZnO film reveals the presence of three modes centered around 274, 475 and 505 cm-1, in addition to the peaks typically expected for wurtzite ZnO. These additional modes occur at frequencies where modes due to ZnO are symmetry forbidden (evidently absent in the undoped ZnO film), indicating that these anomalous modes (AMs) are associated with incorporation of Al dopant. The integrated intensity of the mode at ~274 cm-1 (AM1) increases with increase in RF power up to 150 W and then decreases. On the other hand, the peaks at ~475 (AM2) and 505 (AM3) cm-1 show an exponential increase with RF power. The Urbach energy, which is a measure of disorder in the system, was determined from the transmittance plots of the samples. It shows a trend similar to that of variation in intensity of AM1, indicating strong effect of structural disorder induced by RF power on lattice dynamic behavior. On the other hand, the intensity evolution profiles of AM2 and AM3 are nearly same as the evolution of RF power dependent carrier concentration n obtained from the Hall measurement of the samples, which suggest direct correlation of scattering efficiency of these modes with RF power-dependent dopant concentration.
11:45 AM - S1.7
Large-area, Low-temperature Deposition of Chalcopyrite Absorbers for Thin Film Solar Cells by Reactive Magnetron Sputtering.
Klaus Ellmer 1 , Stefan Seeger 1
1 Solar Fuels, Helmholtz-Zentrum Berlin, Berlin Germany
Show AbstractSince more than 30 years magnetron sputtering is the mostly used large-area deposition method in fields like architectural and low emissivity glass coatings, mirrors and absorbers for solar concentrators, magnetic films for hard disks or hard coatings for tools, i.e., mainly for metals, oxides and nitrides. Today, magnetron sputtering is also used in the expanding thin film photovoltaics industry for metallic back contacts (Ag, Mo) and transparent, conductive window layers (ITO, ZnO). However, it is not yet applied on a technical scale for the absorber layers in thin film solar cells, i.e., for the active semiconductors 1. In this article, the specific obstacles are outlined, which hindered the use of magnetron sputtering for active semiconducting layers up to now. The energies of species (sputtered atoms, positive and negative ions, energetic neutrals) are discussed and its influence on the film growth, especially of reflected neutral argon atoms (Ar0) and negative ions (O-, S-, Se-) accelerated away from the target towards the growing film 2. Due to the low defect formation energies of semiconductors, tailoring the discharge conditions (low particle energies) is mandatory for the preparation of semiconducting films of high electronic quality.The possibilities of reactive magnetron sputtering (RMS) are demonstrated for the deposition of active sulfidic and selenidic absorber films. For the absorber CuInS2 it was shown for the first time, that films of very good electronic properties, comparable to films, which were prepared by thermal methods, can be grown by RMS. RF-excited magnetron sputtering is advantageous with respect to a low H2S consumption in the sputtering process. These results open the way for a future manufacturing of complete thin film solar cells for the prospective energy supply of mankind by reactive magnetron sputtering.1K. Ellmer, in Low Temperature Plasmas. Fundamentals, Technologies and Techniques, edited by R. Hippler, H. Kersten, M. Schmidt, and K. H. Schoenbach (Wiley-VCH, Berlin, 2008), p. 675.2S. Seeger, K. Harbauer, and K. Ellmer, J. Appl. Phys. 105, 053305 (2009).
12:00 PM - S1.8
Effect of rf Substrate Bias on Pulsed DC Magnetron Sputtered Vanadium Oxide Thin Films for Infrared Focal Plane Arrays.
Hitesh Basantani 1 , Myung-Yoon Lee 2 , Jing Li 3 , Bharadwaja Srowthi 3 , E. Dickey 3 , T. Jackson 2 , M. Horn 1
1 Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractHigh resolution, portable night vision cameras rely on uncooled infrared focal plane arrays to detect wavelengths in the 8-14 μm region. These arrays consist of MEMS microbolometer pixels as small as 17 μm × 17 μm that are fabricated on CMOS read-out circuitry (ROIC). Vanadium oxide thin films are often used as the imaging layer in the microbolometers because they have a high temperature coefficient of resistance (TCR) and low resistivity. These films have been commercially made for over two decades using ion beam sputtering. In this presentation, we focus on fabrication of VOx layers via pulsed DC reactive magnetron sputtering of a vanadium target. In particular, this paper reports on the effect of rf substrate bias on the structure and electrical properties of vanadium oxide (VOx) thin films processed via pulsed-dc sputter deposition. The VOx films were deposited using pulsed DC (20 kHz, 90% duty cycle) magnetron reactive sputtering with various Ar:O ratios at pressures between 2.5 and 10 mTorr without substrate heating. The substrate rf bias was varied between 0-40 Watts during deposition of the VOx thin films. Our earlier work has indicated that VOx films processed without substrate bias have resistivity ≤ 1 ohm-cm and consist of fcc rocksalt type VOx nanocrystallites in an amorphous matrix. On the other hand, cross-section transmission electron microscopic studies of films fabricated with a substrate bias indicated formation of a nanocrystalline columnar microstructure with micro-twins embedded in them. Electrical properties such as resistivity, temperature coefficient of resistivity, and 1/f noise of VOx films are compared as function of substrate bias conditions. Films processed with rf substrate bias exhibited lower resistivity and higher TCR values than unbiased samples deposited under identical conditions (Ex: ~ 0.05 ohm.cm resistivity sample exhibited TCR values ~ -2.2% per K with rf substrate bias as opposed to 0.1 ohm.cm with TCR of ~-1.7% per K). The rf bias during the film growth dramatically changes the structure and thereby changes the electrical properties. We demonstrate that it is possible to deposit VOx thin films for microbolometers applications using pulsed DC reactive sputtering with rf substrate bias that have electrical properties equal or surpass films currently fabricated via ion beam sputter deposition.
12:15 PM - S1.9
Influence of Hydrogen Gas on the Synthesis and Properties of Hexagonal Boron Nitride Nanowalls Prepared by Unbalanced RF Magnetron Sputtering.
Boumédiène BenMoussa 1 , Christian Borschel 2 , Jan D'Haen 1 3 , Julien Barjon 4 , Marc Saitner 1 , Ali Soltani 5 , Vincent Mortet 1 3 , Carsten Ronning 2 , Marc D'Olieslaeger 1 3 , Hans-Gerd Boyen 1 , Ken Haenen 1 3
1 Institute for Materials Research, Hasselt University, Diepenbeek, Limburg, Belgium, 2 Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Jena Germany, 3 Division IMOMEC, IMEC vzw, Diepenbeek Belgium, 4 Groupe d’Etude de la Matière Condensée (GEMaC), CNRS- Université de Versailles Saint-Quentin-en-Yvelines, Meudon France, 5 , Institut d'Electronique de Microélectronique et de Nanotechnologie, Villeneuve d'Ascq France
Show AbstractAs shown by Watanabe and co-workers, pure hexagonal BN (h-BN) crystals can support advanced applications based on its luminescent properties, and more recently, even as an ideal substrate material for high quality graphene electronics [1-4]. While the high pressure, high temperature (HPHT) technique produces pure high quality crystals, the technique itself is rather cumbersome, leading to small, irregular crystals that are difficult to handle due to their fragile nature.Here, the easy scalable and cost effective reactive radio frequency (RF) magnetron sputtering process is used with a hexagonal BN target to deposit thin h-BN structures. However, a persistent problem in the synthesis of BN is contamination with oxygen and carbon. It is shown that the addition of H2 to the N2/Ar mixture used during the deposition process, clearly suppresses the incorporation of these elements, reducing their combined level below 5 %. As a result, a quasi-perfect stoichiometry of the material was shown by combining energy dispersive X-ray analysis (EDX), Rutherford backscattering spectroscopy (RBS), and X-ray photoelectron spectroscopy (XPS). Different N2/Ar/H2 gas compositions were used in combination with silicon, quartz or fused silica substrates, to deposit films of different thickness at a rate of 100 to 125 nm/h. Raman and Fourier transform infrared (FTIR) spectroscopy revealed the sp2 nature of the bonds, confirming the h-BN nature of the layers.As an unforeseen side effect, the H2 addition also has an enormous influence on the structure and surface morphology. Whereas N2/Ar plasmas lead to granular films, atomic force microscopy (AFM) and scanning electronic microscopy (SEM) surprisingly revealed the presence of h-BN nanowalls when a few % of H2 is added. The vertically positioned 2D structures consist out of several hexagonal BN sheets [5], with film thickness dependent dimensions and density. Where a 200 nm thick film shows densely packed walls of ~ 100 nm in width, thicker films become more porous, with ~ 1 µm wide walls that cover the surface more sparsely. X-ray diffraction (XRD) and transmission electron microscopy (TEM) prove that the (002) planes are vertically positioned with respect to the substrate surface. A TEM image cross-section image exposes a dense layer of material at the substrate-film interface, which gradually evolves into the 2D nanowall structures observed at the surface. Finally, spectral cathodoluminescence (CL) measurements were carried out to assess the opto-electronic properties and the influence of the H2 addition on them.[1] K. Watanabe, T. Taniguchi, H. Kanda, Nat. Mater. 3/6 (2004), 404-409.[2] Z. Remes, M. Nesládek, K. Haenen, K. Watanabe, T. Taniguchi, phys. stat. sol. (a) 202/11 (2005), 2229-2233.[3] K. Watanabe, T. Taniguchi, T. Niiyama, K. Miya, M. Taniguchi, Nat. Photonics 3/10 (2009), 591-594.[4] C. R. Dean et al., Nat. Nanotech. 5 (2010), 722-726.[5] J. Yu et al., ACS Nano 4/1 (2010), 414-422.
12:30 PM - **S1.10
Quasicrystals and Complex Metallic Alloys: Surface Structure and Thin Film Growth.
Fournee Vincent 1
1 UMR 7198 CNRS-Nancy Universite-UPV Metz, Institut Jean Lamour, Nancy France
Show AbstractQuasicrystals are nonperiodic, yet well-ordered intermetallics that were discovered 25 years ago. Their order does not rely on a three-dimensional periodic arrangement of a unit cell but is based on a specific packing of clusters comprising several tenths of atoms with icosahedral or decagonal symmetry. They are thus considered as a new state of condensed matter, different from crystalline or amorphous materials. As a consequence of this unique crystallographic structure, quasicrystals exhibit unexpected physical properties for metallic compounds. In fact, many Al-based quasiperiodic phases behave much more like semiconductors rather than metallic systems. I will discuss some aspects of these fascinating materials, with a special interest in the understanding of the structure-property relationship at their surfaces prepared in ultra high vacuum conditions and in thin films grown by magnetron sputtering.
Symposium Organizers
JoseLuis Endrino Instituto de Ciencia de Materiales de Madrid
Andre Anders Lawrence Berkeley National Laboratory
Joakim Andersson Uppsala University
David Horwat Institut Jean Lamour
Mykola Vinnichenko Institute of Ion Beam Physics and Materials Research
S7: Poster Session: Plasma-assisted Processing and Synthesis
Session Chairs
Sunnie Lim
Mykola Vinnichenko
Thursday PM, April 28, 2011
Salons 7-9 (Marriott)
1:00 AM - S7: PLASMAPOSTER
S7.7 Transferrerd to S6.7
Show AbstractS6: Ionized Physical Vapor Deposition
Session Chairs
David Horwat
Mykola Vinnichenko
Thursday PM, April 28, 2011
Room 3004 (Moscone West)
2:30 PM - **S6.1
Recent Advances in Metastable Oxide Films and Artificial Heterostructures Grown by Laser Ablation.
Adrian David 1 , Ulrike Lueders 1 , Philippe Boullay 1 , R. Fresard 1 , Wilfrid Prellier 1
1 CRISMAT/UMR6508, CNRS/ENSICAEN, Caen France
Show AbstractThin films and artificial heterostructures offer excellent opportunities to manipulate the strain and chemical heterogeneity in order to exhibit completely new or enhance the properties, which were absent in the parent compounds. It is for example possible to overcome the natural preference for disorder or low-dimensional ordering in certain materials by controlling the location of cations. Consequently, there has been recently growing interest in tailoring materials in thin films forms, having original properties that can not be obtained in the form of bulk materials, using the process of the pulsed laser deposition technique.In this talk, I will illustrate the above approach by presenting the growth and characterizations of technologically important novel oxides. In particular, I will show our latest results on the synthesis and characterization of metastable phases [1] as well as the physical properties and structural characterization of complex superlattices made from perovskites.[2,3]Partial support of the Ministère des Affaires Etrangères through the CEFIPRA program (3908-1) and STRAR is also acknowledged.[1] A. David et al., Appl. Phys. Lett. [2] U. Lüders et al., Phys. Rev. B B 80, 241102 (2009)[3] S. Thota et al., Appl. Phys. Lett. 97, 112506 (2010).
3:00 PM - **S6.2
Correlation between Titanium Oxide Microstructure and Plasma Chemistry and Energetics.
Marie Paule Delplancke 1 , Igor Zhirkov 1 , Carlo Paternoster 1 , Stanislav Mraz 2 , Jochen Schneider 2 , Stephanos Konstantinidis 3 , Rony Snyders 3 4
1 Chemicals and Materials, Université libre de Bruxelles, Brussels Belgium, 2 Materials Chemistry, RWTH Aachen University, Aachen Germany, 3 Chimie des Interactions Plasma Surface, CIRMAP, Université de Mons, Mons Belgium, 4 , Materia Nova Research Center, Mons Belgium
Show AbstractPhase transformations (including nucleation and growth mechanisms) which can occur within the plasma phase or at the plasma/surface interface have been investigated for several decades due to their significant influence on the properties of the synthesized materials. Nucleation, growth and coalescence are strongly affected by the mobility of species at the surface, by the energy of bombarding particles (neutrals, ions and electrons) and by the atomic and thermodynamic properties of the substrates. In most cases, the plasma phase is seen as a homogeneous reservoir of species in a steady-state. Systematic investigations of the effect of deposition parameters onto the composition and the energy distribution functions of the species present in plasmas used for vapor phase condensation are at this point rather limited. The phase diagram of TiO2 is quite rich with the existence of three crystalline phases (anatase, rutile and brookite) in addition to an amorphous phase. The properties of TiO2 films are highly dependent on the phases in presence. TiO2 films can be synthesized by numerous physical vapor deposition methods which all have their own characteristics in terms of plasma chemistry and energetics. Our strategy is to compare TiO2 coatings prepared using three different plasma processes (dc and rf reactive magnetron sputtering, reactive arc discharge, and reactive HiPIMS) and in each case to correlate the plasma chemistry and energetics with the films characteristics in order to draw a “phase diagram” of TiO2 as a function of the plasma features. The three methods provide a wide spectrum of plasma characteristics which will influence the films constitution and microstructure. The results of this study based on a thorough characterization of the plasma parameters (composition, energy distribution of ions, electrons and neutrals, fluxes of species…) and of the deposited films will be presented and trends will be given. Acknowledgements: This work is carried out in the framework of the P6/08 project of the Interuniversity Attraction Poles Programme – Belgian State – Belgian Science Policy
4:00 PM - **S6.3
Time Resolved Optical Studies of Charge State Evolution in High Current Pulsed Arc and Magnetron Discharges.
Marcela Bilek 1 , Roberto Sangines de Castro 1 , Anne Weeks-Ross 1 , Ben Treverrow 1 , Luke Ryves 1 , John Pigott 1 , David McKenzie 1
1 School of Physics, University of Sydney, Sydney, New South Wales, Australia
Show AbstractThe utilisation of pulsed plasmas in materials synthesis is rapidly growing due to a number of advantages over their continuous mode counterparts. A major operational advantage is that the pulsed mode is much less affected by problems associated with instabilities, surface charging of substrates and cathode or target poisoning and as such typically has wider process windows. The plasmas are typically transient, operating far from equilibrium, at least in the early stages, and showing an evolution of parameters through the pulse. Resolving the transient phenomena and determining their effects on plasma conditions at the substrate is a prerequisite for achieving good control over film deposition.In this paper, we employ a suite of optical plasma diagnostics to compare charge evolution in a pulsed cathodic arc and with that observed in a high powered pulsed magnetron discharge. The arc system is a multi sourced high current centre triggered cathodic arc system operating in a high power pulsed mode [1,2] previously developed in our laboratory. This system has been used for the deposition of nanostructured materials such as MAX phases [3], nanoscale multilayers [4] and phase separated nanostructured coatings [5]. The centre triggered design allows us to correlate changes in the charge states produced, detected with time resolved optical emission spectroscopy, with the numbers of cathode spots present and their separations on the cathode surface, as measured by fast framing photography. The results indicate that elevated charge states are produced in the early stages of the pulse due to short range coupling between cathode spots.The multi-source sputtering system is driven by a pulsed power supply capable of producing constant voltage pulses up to 1000V at currents up to 450A. Our time resolved optical emission studies show that high charge states peak at the end of the pulse. Differences between the evolution of the first ionised state and that of the higher charge states indicate that distinct electron populations may be responsible for their creation: one characterised by LTE and a temperature close to 1 eV while the other comprising fast secondary electrons accelerated through the sheath.References: [1] T.W.H. Oates, J. Pigott, D. R. McKenzie, and M.M.M. Bilek, Review of Scientific Instruments, vol. 74, pp. 4750-4754, (2003)[2] Sangines R, Bilek MMM, McKenzie DR, Plasma Sources Science and Technology, 18 (4) Article Number:045007 (2009) [3] Rosén J, Ryves L, Persson POÅ, Bilek MMM, Journal of Applied Physics, 101 (5): Art. No. 056101 (2007)[4] Persson POA, Ryves L, Tucker MD, McKenzie DR, Bilek MMM, Journal of Applied Physics, 104 (7), Article Number: 074317, (2008)[5] Abrasonis G, Kovacs GJ, Ryves L, Krause M, Mucklich A, Munnik F, Oates TWH, Bilek MMM, Moeller W, Journal of Applied Physics, 105(8 ) Article Number: 083518 (2009)
4:30 PM - S6.4
Surface Modifications by Gasless Sputtering of Copper and Nickel.
Joakim Andersson 1
1 Solid State Electronics, Engineering Sciences, Uppsala Sweden
Show AbstractGasless sputtering is a recent addition to the large family of physical vapor deposition methods, where self-sustained high power impulse sputtering pulses of high sputter yield elements are initiated by arc discharges. By applying this method to copper targets it was for the first time possible to create a substrate ion current in excess of the discharge current, which facilitates new experiments on surface modifications. It also offers a way to elucidate the effects of the sputter gas as used in conventional high power impulse magnetron sputtering. Comparisons in high aspect ratio trench lining show that the mere presence of gas reduces the coverage attainable. Additionally, the presence of gas also reduces the deposition rate of copper. Gasless sputtering may therefore be a viable improvement for coating complex geometry components with copper. Gasless sputtering has also been achieved with nickel and silver, and surface modifications using nickel ions will be presented.
4:45 PM - S6.5
Oxide Thin Films Prepared by Glancing Angle Deposition (GLAD) as Host for the Fabrication of Functional Hybrid Materials.
Lola Gonzalez-Garcia 1 , Juan Ramón Sanchez-Valencia 1 , Juan Ramón Sanchez-Valencia 1 , Pedro Castillero 1 , Julian Parra 1 , Ana Borras 1 , Angel Barranco 1 , Agustin Gonzalez-Elipe 1
1 , Instituto de Ciencia de Materiales de Sevilla (CSIC-Uni. Sevilla), Sevilla Spain
Show AbstractThis work reports about the preparation of porous oxide thin films by glancing angle physical vapor deposition (GLAD-PVD) and their use as host for the incorporation of different organic or inorganic components. The obtained hybrid thin films present outstanding functional properties of interest for a large variety of applications. Results are reported about the preparation and characterization of SiO2 and TiO2 host thin films. A particular attention is paid to the determination of morphology, porosity and surface roughness of the films as they are critical parameters for their use as host for the development of different kinds of functional materials. Examples are reported where the GLAD thin films are used as porous Bragg reflectors, photonic gas sensors, dye sensitized photovoltaic cells or films with metal plasmon activity and dichroism behavior. For each of these applications different strategies have been developed to incorporate into the films foreign fluorescence molecules, active polymers or metal nanoparticles. These strategies are critically discussed and the functional behavior of the composite films/systems briefly outlined.
S7: Poster Session: Plasma-assisted Processing and Synthesis
Session Chairs
Sunnie Lim
Mykola Vinnichenko
Friday AM, April 29, 2011
Salons 7-9 (Marriott)
9:00 PM - S7.1
Structure and Properties of Nanocrystalline TiN Films by ICP Assisted Magnetron Sputtering.
Sung-Yong Chun 1 , Man-Geun Han 1 , Kyung-In Kim 1
1 Advanced Materials Eng., Mokpo National University, Jeonnam Korea (the Republic of)
Show AbstractThe generation of high-density plasma is important for plasma assisted deposition, because high-density plasma can be used as activation source for lowering the substrate temperature and enhancing the film quality. A higher plasma density will result in a higher degree of ionization of the metal atoms in the gaseous phase, which enables maximum control over the deposited films. Film deposition with ICP was primarily investigated to obtain uniform coverage in the trenches of the high aspect ratios in ULSI processing. However, few studies on the mechanical properties and microstructure of coatings deposited with ICP have been reported. Owing to the high ion density, coatings deposited by ICP assisted sputtering would be expected better mechanical properties with denser microstructures than coatings formed by conventional deposition methods.In this work, we report the microstructure, crystallographic structure, crystallite size, surface roughness and nano-hardness of nanocrystalline TiN films prepared by ICP assisted magnetron sputtering under various powers. Acknowledgments:Following are results of a study on the "Human Resource Development Center for Economic Region Leading Industry" Project, supported by the Ministry of Education, Science & Technology(MEST) and the National Research Foundation of Korea(NRF).
9:00 PM - S7.11
Long-lasting Behaviors of Superhydrophilicity on Nanostructured Si-DLC Film.
Seong JIn Kim 1 , Jin Woo Yi 1 , Myoung-Woon Moon 1 , Ho-Young Kim 2 , Kwang-Ryeol Lee 1
1 , Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 , Seoul National University, Seoul Korea (the Republic of)
Show Abstract Complete wetting surface is a surface providing spontaneous transportation of water. With well-organized structure acting as a way, spontaneous transportation of water to a desired direction is made without any energy requirement. However, high surface energy of complete wetting surface limits its potential to commercial applications by easily recovering to a hydrophobic state. Here, we introduce nanostructure superhydrophilic surface of DLC (diamond-like carbon) containing silicon oxide as a long-lasting surface. We deposited Si-DLC by RF-CVD (radio frequency – chemical vapor deposition) method with a mixture of benzene and silane gases. And hydrophilic Si-O group and nanomorphology are made on the surface during following oxygen plasma treatment. We found the relation between long-lasting behavior and chemical & morphological properties of Si-DLC film from the aging experiments up to 20 days in the air and water immersion. And we have further applied the long-lasting hydrophilic surface on fiber network of a non-woven fabric.
9:00 PM - S7.12
Low Power Plasma Treatment of PET Substrates to Achieve Nano/Micro Structures.
Zeinab Sanaee 1 , Shams Mohajerzadeh 1 , Mohammad Abdolahad 1 , Faramarz S. Gard 2
1 Electrical engineering, University of Tehran, Tehran Iran (the Islamic Republic of), 2 Physics, Sultan Qaboos University, Muscat Oman
Show AbstractPolyethylene terephthalate (PET) is a widely used polymer for industrial applications especially for packaging and food industry. This material enjoys good physical and electrical characteristics such as flexibility, transparency, high thermal resistance and low cost making it a suitable choice for many industrial applications. The plasma treatment of PET is important to improve its surface properties, as an application of which one can point out the increase in its resistance against gas permeability. The improvement in surface adhesion could be of great importance for biological applications. In this paper, gaseous plasma treatments on PET substrates have been performed using oxygen, hydrogen and SF6 gases and in a wide range of plasma exposure times to investigate their effects on PET samples. Different analyses such as optical transmission/reflection, contact angle measurement, XPS, FTIR and SEM analyses have been extensively exploited on various samples. The plasma treatment has been carried out in a radio-frequency (13.56 MHz) reactive ion etching unit with plasma powers ranging from 50 to 250 W and durations ranging from 2 to 45 mins. The pressure of the reactor is controlled by the flows of inlet gases.The high-resolution SEM images reveal the evolution of micro and nano-structures on the surface of treated PET foils. Upon exposure to oxygen plasma treatments with extended periods, agglomerated nanometric and micrometric features are formed on the surface of PET, creating highly three-dimensional forest-like structures. In the case of oxygen gas inlet, it has been observed that by increasing the plasma exposure time, first nano-grass structures are observed after short intervals whereas micro-forest structures are formed after long treatment times. After two minutes of O-plasma with 250 watts power and 50 sccm flow, nano grass features with typical size of about 40nm are formed, while with increasing the plasma treatment time to 45 minutes some agglomerated features with size of about 1µm can be observed. XPS and FTIR results support the evolution of certain functional groups in the plasma treated sample as carboxylic (O-C=O) and ester groups. In the case of hydrogen-treated samples, the gas permeability shows a considerable drop, which could be due to the formation cross-linked structures. By using SF6/oxygen we have been able to obtain nanometric nanowires on PET with a height of 2-5um. As an immediate application, we have observed a considerable reduction in the polymer gas permeability, making it suitable for flexible electronics. In addition, and as a hectic application, we have investigated the use of plasma treated PET foils for biological applications where human cells behave differently on the structured surfaces of such substrates. More details about this effect will be presented.
9:00 PM - S7.14
Fabrication of High Aspect Ratio Wrinkles on a Soft Polymer by GLAD.
Tae-Jun Ko 1 2 , Myoung-Woon Moon 2 , Kwang-Ryeol Lee 2 , Kyu Hwan Oh 1
1 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Interdisciplinary and Fusion Technology Division, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractWrinkle, one of mechanical instabilities, was generally treated as harm in thin films. This concept has changed recently with the development of techniques for controlled patterning of polymer and hard surfaces and the emergence of novel applications that benefit from the created patterns. These applications are used from building cell templates and nanochannels for protein condensation to manufacturing smart adhesives and optical grating devices.These techniques are based on inducing a strain mismatch between a stiff thin film and a soft substrate, causing the instability and wrinkling of the stiff film. However, the ratio of wrinkle amplitude/wavelength is generally limited to 1/10 in current deposition method and it is of the limiting factors in many fields. For fabricating of high aspect ratio wrinkles, we used glancing angle deposition method (GLAD), which is a physical vapor deposition method used to fabricate functional thin films with a columnar morphology, for deposition of an amorphous carbon film on a PDMS surface. During carbon deposition, the anode voltage was kept at a constant value of 1 kV and a radio frequency (r.f.) bias voltage was applied to the substrate holder at a bias voltage of -200 V. And the carbon deposition time was kept between 30 s to 50 min, while the incident angle of hydrocarbon ion was varied from 0° to 75°.It was shown that aspect ratio of wrinkles increased from 1/10 to 2.5 as increased the incident angle of hydrocarbon ion from 0° to 75° and keep the same wavelength of wrinkles which is relatively insensitive to the deposition angle.In this study, we show that the amplitude of the created patterns can be varied between several nm to submicron size by changing the carbon deposition time, and we demonstrate a potential application of the high aspect ratio wrinkles for changing mechanical property and band gap of the surface.
9:00 PM - S7.15
Chemically-induced Responsive Thermal Volume Transformation with Ultrathin PECVD Polymers.
Kyle Anderson 1 , Michael McConney 2 , Rachel Jakubiak 2 , Timothy Bunning 2 , Vladimir Tsukruk 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractResponsive materials, including polymer thin films, are an essential component in many applications where they act as sensors to a variety of stimuli including heat, moisture and pH. Use of thin films in sensing applications typically require and benefit greatly from rapid response times, allowing for many cycles per second for greater resolution of the collected data. Films of pNIPAAM and pHEMA were fabricated via plasma enhanced chemical vapor deposition (PECVD) on silica substrates. These hydrophilic materials swell when exposed to water vapor resulting in measurable changes in film thickness and refractive index. Using a temperature and humidity controlled environment, the change in film thickness and index was observed with spectroscopic ellipsometry as a function of vapor concentration. The amount of vapor absorbed by the films was measured precisely with a climate controlled quartz microbalance. With exposure to moisture, the water absorbed from the surface of the film swells the polymer matrix increasing the physical thickness and a decrease in the refractive index is seen in relation to the change in thickness of the film. Both phenomena occur rapidly, at the same time with the refractive index change relating to the change in crosslinking density as the film expands and contracts. Precise amounts of vapor absorbed by the film are measured with a climate controlled QCM which allows for specific flow rates of vapor into the chamber which shows that more moisture is absorbed on the surface at higher flow rates. As the film is exposed to the moisture, it is absorbed on the thin film and will cause a fast swelling in the film (millisecond transition time) resulting in a measurable change in thickness and refractive index of the films. The speed and degree of response (change in thickness and refractive index) is an indicator of the sensitivity of the materials and can be tuned based on the deposition conditions in the plasma chamber to control the crosslinking density of the network.
9:00 PM - S7.17
Properties of Highly Dense Pulsed Filter Arc Deposited Diamond-like Carbons Containing Metal Clusters.
Jaume Caro 1 , Raul Bonet 1 , Jose Endrino 2
1 , CTM Centre Tecnologic, Manresa Spain, 2 , Instituto de Ciencia de Materiales de Madrid, Madrid Spain
Show AbstractDiamond like carbon (DLC) has many superior properties such as high hardness, low coefficient of friction, and inertness to chemicals. However, the application field of DLC films is sometimes restricted by reduced adhesion and high residual stresses. This problem can be overcome by incorporating transition metals into the carbon matrix. It is also known that the sp3 fraction and stress can be controlled with the increase of negative pulsed substrate voltage. The actual physical properties of metal-containing DLC depend as much on the density and the metal content as they do on the sp3 content and the formation of metal-carbon bonds. The formation of metal clusters into DLC coatings plays a critical role in their electrical conductivity and can therefore be used to manufacture various types of resistive sensors. We have compared the mechanical, frictional and morphological characteristics of various metal-containing DLC coatings deposited onto silicon and stainless steel metal substrates. The samples were prepared by two different pulsed filter cathodic arc systems, namely the first system was a laboratory scale unit employing a “triggerless” operation and integrating three quarter-inch cathodes into a single miniature source and the second system was a pilot production unit composed of two separated sources with 10mm cathodes and detached magnetic guided filters. Both of these systems are ideal for depositing highly dense metal-containing DLC films by plasma immersion ion implantation and deposition due to the incorporation of 90-degree curved macroparticle filters and the possibility to synchronize fully ionized metal and carbon plasmas with specimen pulsed bias voltage. The optimization of deposition parameters and conditions in order to achieve nanocomposite hydrogen-free DLC films of the highest quality is here discussed.
9:00 PM - S7.2
Improvement of Stability in Gd2Zr2O7 Coating Material by Plasma-assisted Process.
Kee Sung Lee 1 , Dong Heon Lee 1 , Tae Woo Kim 1 , Yeon Gil Jung 2 , Ungyu Paik 3
1 School of Mechanical Engineering, Kookmin University, Seoul Korea (the Republic of), 2 School of Nano&Advanced Materials Engineering, Changwon National University, Changwon Korea (the Republic of), 3 Department of Energy Engineering, Hanyang University, Seoul Korea (the Republic of)
Show AbstractGadolinium zirconate (Gd2Zr2O7) film has extensively received much attention as an oxide ion conductor, optoelectronic device, luminescence sensor, and thermal barrier coatings. Its particular pyrochlore structure is known to be related with unique electrical and thermal stability with improved radiation resistance and optical parameters. However, stability of coating during operation of device in extreme electrical, optical or thermal atmosphere is still a problem to solve it. Delamination of film is one of the problems, which requires a technology to develop for reliable, reproducible, and cost-competitive coatings. In this study, specifically, we demonstrate designing of coating microstructure to improve stability of Gd2Zr2O7 layer. Deliberate cracks in the Gd2Zr2O7 layer are introduced to release mechanical stress and enhance the lifetime in this presentation. In particular, FEM analyses are undertaken for designing stable Gd2Zr2O7 coatings. Plasma-assisted experiments are undertaken for comparison. Multilayer containing sub-layer with different thermal expansion coefficient is one way to design the deliberate cracking structure in the layer. Controlling the parameters of plasma-process is the other way to establish the cracking microstructure. Stability experimental tests provide Gd2Zr2O7 coatings designed by cracking structure exhibit longer lifetime. The results from FEM analyses and experiments indicate the advantage of Gd2Zr2O7 coatings for alleviating stress, and thus improving stability.
9:00 PM - S7.3
Structural and Optical Study of ZnO Thin Films Prepared by Reactive Magnetron Sputtering.
Adolfo Mosquera 1 , David Horwat 2 , Luis Vazquez 1 , Patrice Miska 2 , Jose Endrino 1
1 Surfaces and Coatings, ICMM-CSIC, Cantoblanco-UAM Spain, 2 Département CP2S, Institut Jean Lamour (UMR CNRS 7198), Nancy France
Show AbstractReactive magnettron sputtering is a widely used deposition technique because it can provide high deposition rates onto a large area while offering good control of the composition of the films. The properties of reactively sputtered films mainly depend on parameters such as oxygen flow rate, oxygen partial pressure, deposition time, and sputtering regime mode (metal, transition or reactive). However, ZnO films of high quality are difficult to achieve due to slight process instabilities that can affect the growth mode.Zinc oxide thin films of different thickness were synthesized onto glass and silicon substrates by dc reactive magnetron-sputtering technique using a pure metal target. Two reactive oxygen flow rates (6.3 sccm and 7.0 sccm) were employed during the deposition of the samples. The effect of the deposition conditions (i.e. deposition time and sputtering regime mode) on the microstructural evolution and optical properties of the films is here investigated. Structural investigations were carried out by Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD), showing the formation of polycrystalline films with preferencial c-axis orientation parallel to the surface of the samples. Changes in film roughness were determinated by both AFM and perfilometer, an increase in the film roughness with thickness was observed in films deposited at 6.3 sccm, however, the films deposited using 7.0 sccm oxygen flow, had similar average surface roughness, independly of the film thickness. All the films were insulating and exhibited a high optical transmittance of 95% in the visible region. For the UV region, in the wavelength range between 300-400 nm, the presence of a band was observed. The transmittance of this band decreases with film thickness for both types of films. Photoluminisence measurements were performed to determine the presence of excitons that could be correlated to the film morphology affecting the UV transmitance.
9:00 PM - S7.4
Optical and Electrical Characterization of ZnO Films Co-implanted with O and As Ions.
Chang Oh Kim 1 , Seung Bum Yang 1 , Hyoung Taek Oh 1 , Suk-Ho Choi 1 , K. Belay 2 , Rebert G. Elliman 2
1 Department of Applied Physics, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of), 2 Electronic Materials Engineering Department, Australian National University, Canberra, Australian Capital Territory, Australia
Show AbstractOptical and electrical characteristics of ZnO films co-implanted with O and As ions have been investigated by photoluminescence (PL), Hall-effect, and current-voltage (I-V) measurements. 100-nm-thick ZnO films grown on n-type Si (100) wafers by RF sputtering were implanted firstly with 30 keV O ions of 1 x 1014 and 1 x 1015 cm-2 fluences and secondly with 100 keV As ions of 1 x 1014, 5 x 1014, and 1 x 1015 cm-2 fluences at room temperature, and subsequently annealed at 800 oC for 20 min in a N2 ambient. The co-implanted films with a fluence of 1 x 1015 As cm-2 exhibit p-type behaviors with 3 ~ 6 x 1018 cm-2 hole concentration, 30 ~ 33 cm2/Vs mobility, and 0.049 ~ 0.062 Ω cm resistivity, consistent with the observation of dominant PL peak at 3.357 eV that is associated with the neutral acceptor bound exciton. The I-V curves also show rectifying p-n junction behavior in the co-implanted p-type ZnO/n-type Si wafer diodes. Other As-implanted samples with or without O ions show n-type or indeterminable doping characters. These results suggest that the O implantation plays a key role in forming p-type ZnO films. Possible doping mechanisms are discussed with reference to natural defects of ZnO films.
9:00 PM - S7.5
Synthesis of Nano-structured Alpha and Beta Tantalum by Magnetron Sputtering.
Anahita Afshin navid 1 , Andrea Hodge 1
1 , University of Southern California, Los Angeles, California, United States
Show AbstractThe phase formation in magnetron sputtered tantalum is presented as a function of residual stress and internal plasma conditions. The formation of stable body centered cubic (BCC) phase and metastable tetragonal tantalum was observed on films deposited on a Si substrate at pressures between 0.3 and 1.4 Pa. The results demonstrate the formation of BCC tantalum at 0.7 Pa sputtering pressure and various powers ranging from 50 watts to 200 watts. Other sputtering pressures did not yield a BCC structure but rather mixed BCC/tetragonal or a tetragonal phase. In addition, the correlation between hardness, residual stress and texture development are presented for all conditions. The impacts of plasma kinetics and impurities levels are investigated in respect to the phase formation at multiple sputtering conditions.
9:00 PM - S7.6
Structural Characterization of Ti-In-N Films Deposited by Magnetron Sputtering.
Magaret Nowicki 1 , James Krzanowski 1 , Luis Vazquez 2 , Jose Endrino 2
1 Mechanical Engineering, University of New Hampshire, Durham, New Hampshire, United States, 2 , Instituto de Ciencia de Materiales de Madrid, Madrid Spain
Show AbstractThe application of thin coatings for tribological applications can be enhanced by employing films consisting of hard phases for wear resistance and soft phases for friction reduction. In the present study, we have examined TiN-Indium composite films for this purpose. Films were deposited by simultaneous sputtering of Ti and In in a mixed Ar/Nitrogen atmosphere. The deposited films were examined using scanning electron microscopy, x-ray diffraction, XPS, atomic force microscopy and nano-indentation testing. The film composition showed non-linear behavior as a function of sputter gun power. The AFM and SEM results showed morphological features that were strongly dependent on the In content, with higher indium contents giving rougher films. For films deposited with -50V bias, and less than 29 relative % indium, the films had an FCC structure. At higher indium contents (63-82%) x-ray diffraction revealed a structure that was not consistent with either TiN or In. The hypothesis was that two fcc-phases were present, one with a = 0.525 nm and the other with a = 0.4885 nm. At -150V bias, the films had either the TiN structure, In-type structure, or a mixture of the two. Nano-indentation test of the films show low hardness values, in the range of 5-12 GPa.
9:00 PM - S7.8
Evaluation of Solid Lubricants Used in Space Mechanisms Deposited In-situ from the Plasma Phase.
Jose Endrino 1 , Andre Anders 2 , Adolfo Mosquera 1 , Stephen Pepper 3
1 , Instituto de Ciencia de Materiales de Madrid, Cantoblanco-UAM Spain, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 , NASA Glenn Research Center, Cleveland, Ohio, United States
Show AbstractRealistic friction and lubricant degradation rates in vacuum can be determined by use of a Spiral Orbit Tribometer (SOT), a device that operates under vacuum conditions where a ball spirals between two flat metal plates in an “open configuration” inside a vacuum chamber. In this manner, it provides valuable information that can guide the selection of both liquid and solid lubricants used in space applications. In the present study, we have coupled an SOT device with pulsed plasma production of several solid lubricant metals (copper, silver, and a mixture of both) in order to quickly produce results regarding the degradation rates of “freshly” deposited thin metal films in vacuum mechanisms. A pulsed cathodic arc minigun positioned near the rolling ball was employed to shoot high-density metal plasma to the SOT mechanism, while maintaining high vacuum conditions (~10-5 Pa) inside the chamber. The deposited metal film reduced friction and wear caused by the sliding of the ball. The effectiveness of this method to quickly evaluate solid lubricants in vacuum as well as the effectiveness of using pulsed plasma on-demand systems in deployed space mechanisms is here assessed by means of monitoring variations in the coefficient of friction during tribological tests as well as by subsequent observations of wear marks on the surface of the steel 440C ball and guide plates by secondary electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) analytical techniques.
9:00 PM - S7.9
Si Nanowire Fabricated with CF4 Plasma for Superhydrophobic Surface.
Eun Kyu Her 1 2 , Kyu Hwan Oh 1 , Kwang-Ryeol Lee 2 , Myoung-Woon Moon 2
1 Materials Science and Engineering, Seoul National University, Seoul, Seoul, Korea (the Republic of), 2 Interdisciplinary and Fusion Technology Division, Korea Institute of Science and Technology, Seoul, Seoul, Korea (the Republic of)
Show AbstractTo achieve the hierarchy of roughness as observed in lotus leaves, most artificial water-repellent, or superhydrophobic surfaces have nano-asperities on top of micropillars. However, by choosing high aspect ratio of the height over diameter with nano patterns only, the superhydrophobic surface can be obtained. Thus we fabricate surfaces having the Si nanopillars or nanowire on Si wafer plasma-etching with CF4 precursor and subsequent hydrophobic carbon coating.The Si wafers were etched to create the nanowires using r.f. glow discharge of CF4 plasma etching at 30 mTorr and -600V of bias voltage using plasma assisted chemical vapor deposition (PACVD) method. Aspect ratio of nanowire was controlled by time of CF4 plasma treatment from 10 min to 60 min as well as bias voltage from 400 to 800Vb, which produced the height and diameter of nanowires in the range of 40-300 nm and 60-850 nm, respectively. For preparing hydrophobic surfaces, HMDSO gas were used for the deposition of a-C:H:Si:O deposited on each surface by PACVD method.It was shown that static contact angle on the nanowire surfaces increased from 120 to 160 degree as increased the CF4 plasma treatment time and the contact angle hysteresis was drastically decreased for the samples from 10 to 60 min of CF4 plasma treatment from 45 to 15 degree. It has been studied further that the shape of each pillar induced by CF4 treatment can be varied from the mushroom by undercut of Si nanopillars to the sharp cone with additional water-wetting process, which improved the wettability of nanostructured surfaces.