Cengiz S. Ozkan, University of California Riverside
Yury Gogotsi, Drexel University
Huajian Gao, Brown University
Richard B. Kaner, University of California, Los Angeles
Symposium Support Aldrich Materials Science
OO2: Heterostructures and Devices
Sang Ouk Kim
Monday PM, April 21, 2014
Moscone West, Level 2, Room 2008
2:30 AM - *OO2.01
Electronic Properties of Graphene Heterostructures
Philip Kim 1
1Columbia University New York USAShow Abstract
Assembling van der Waals (vdW) materials, hexa boronitride, layered transition metal chalcogenide and many strongly correlated materials, together with graphene, we can construct novel quantum structures. These quantum heterostrutured materials can be further modified by electrochemical intercalation and electrolyte gating. In this talk, I will discuss to develop the method of transferring graphene to two-dimensional atomic layers of van der Waals solids to build functional heterostacks. We will discuss novel electron transport phenomena can occur across the heterointerfaces of designed quantum stacks to realize exotic charge transport phenomena in atomically controlled quantum heterostructures and their derivatives.
3:00 AM - *OO2.02
Understanding the Electrical Properties of Graphene Using the Quantum Capacitance Effect
Steven J Koester 1 Mona A Ebrish 1 Eric J Olson 1 David A Deen 1
1University of Minnesota Minneapolis USAShow Abstract
The quantum capacitance effect in graphene can readily be observed experimentally due to the low density of states near the Dirac energy. In particular, in metal-oxide-graphene structures with thin, high-K dielectrics, the quantum capacitance strongly affects the measurable capacitance as a function of gate voltage. In this work, we show how the quantum capacitance can be utilized to understand numerous properties of graphene, the surrounding dielectrics and even absorbed molecules on the graphene surface. Furthermore, we show that the quantum capacitance can be utilized to realize numerous novel graphene-based devices, including wireless sensors and optical modulators. Finally, the prospects for future materials-related investigations and device applications of quantum capacitance in graphene are described.
3:30 AM - OO2.03
Understanding Magnetoresistance in Manganite-Graphene-Manganite Lateral Spin Valves
Lee Phillips 1 Antonio Lombardo 2 Wenjing Yan 1 Sohini Kar-Narayan 1 Xavier Moya 1 3 Massimo Ghidini 1 4 Francesco Maccherozzi 5 Sampo Hamalainen 6 Sebastiaan Van Dijken 6 Sarnjeet S Dhesi 5 Andrea C Ferrari 2 Neil D Mathur 1
1University of Cambridge Cambridge United Kingdom2University of Cambridge Cambridge United Kingdom3Universitat de Barcelona Barcelona Spain4University of Parma Parma Italy5Diamond Light Source Chilton United Kingdom6Aalto University Aalto FinlandShow Abstract
Long-distance spin transport is a prerequisite for spin-based logic proposals [1,2]. Graphene is attractive for spin transport studies because its low spin-orbit coupling leads to a long spin diffusion length lsf . A local magnetoresistance (MR) study suggested lsf is of order 100 µm in epitaxial graphene , but non-local spin precession studies consistently measure lsf of order 1 µm [5,6]. Local MR measurements require careful interpretation, because MR can arise from diverse physics including anisotropic magnetoresistance in the component materials, local Hall effect, magneto-Coulomb effects and tunnelling anisotropic magnetoresistance (TAMR). The latter in particular can mimic MR signals observed in spin transport.
Here we present large local MR in graphene contacted by epitaxial electrodes of the highly spin-polarized ferromagnet La0.67Sr0.33MnO3 (LSMO). We use a deterministic transfer process  to combine the two materials whose growth conditions are incompatible. The formation of an intrinsic interfacial tunnel barrier generates large device resistances of order 100 M#8486;, making non-local measurements impractical. The large local resistance changes ΔR > 30 M#8486; imply giant lsf values exceeding 500 µm when analysed in spin transport theory. To distinguish spin transport from TAMR, we undertake magnetic imaging of LSMO electrodes by magneto-optical Kerr effect (MOKE) and X-ray magnetic circular dichroism in photoemission electron microscopy (XMCD-PEEM). We conclude that micromagnetic studies provide a health check when interpreting local MR.
 Dery et al., Nature 447, 573 (2007)
 Behin-Aein et al., Nature Nanotechnology 5, 266 (2010)
 Huertas-Hernando et al., Phys. Rev. Lett. 103, 146801 (2009)
 Dlubak et al., Nature Phys. 8, 557 (2012)
 Tombros et al., Nature 448, 571 (2007)
 Han et al., Phys. Rev. Lett. 105, 167202 (2010)
 Reina et al., J. Phys. Chem. C 112, 17741 (2008)
3:45 AM - OO2.04
ALD for Spintronics with Graphene Passivated Ferromagnetic Electrodes as Oxidation Resistant Spin Sources
Marie-Blandine Martin 1 Bruno Dlubak 1 2 Robert S. Weatherup 2 Heejun Yang 1 Cyrile Deranlot 1 Raoul Blume 3 Robert Schloegl 4 Albert Fert 1 Abdelmadjid Anane 1 Stephan Hofmann 2 John Robertson 2 Pierre Seneor 1
1Unitamp;#233; Mixte de Physique CNRS/Thales Palaiseau France2University of Cambridge Cambridge United Kingdom3Helmholtz-Zentrum Berlin fur Materialien und Energie Berlin Germany4Fritz Haber Institute of the Max Planck Society Berlin GermanyShow Abstract
Magnetism is today the main technology in use for data storage and spintronics is at the heart of the information storage revolution, with ferromagnets acting as fundamental building blocks: spin sources or analysers. However, these ferromagnetic metals (e.g. nickel, cobalthellip;) are easily prone to oxidation, detrimental to their performances. In turn, this limits their processability, e.g. with low cost wet processes. Here, we present graphene passivated ferromagnetic electrodes (GPFE) as novel oxidation-resistant spin sources . Nickel lines are coated with graphene in a direct and scalable chemical vapour deposition step. An in-situ X-ray photoelectron spectroscopy study shows that the resulting GPFE are reduced during the growth process and remain resistant to oxidation upon air exposure. The GPFE spin polarisation properties are then measured through a complete vertical spin valve structure with a standard Al2O3/Co spin probe. It appears that GPFE not only retain a spin polarisation, but also present a particular majority spin filtering effect, which eventually leads to the reversal of their spin polarisation. Our results open new promising pathways for the integration of novel processes (e.g. ALD) and materials (organics) in spintronics devices .
 B. Dlubak et al, ACS Nano 6, 10996 (2012).
 M.-B. Martin et al, submitted
OO3: Growth I
Monday PM, April 21, 2014
Moscone West, Level 2, Room 2008
4:30 AM - *OO3.01
Graphene Growth and Applications
James M Tour 1
1Rice University Houston USAShow Abstract
Several new routes to the growth and manipulation of graphene will be discussed. These will include the preparation of large-area (2.3 millimeters) single-domain graphene grown on simple copper foils, preparation of Bernal-stacked bilayer, trilayer and tetralayer graphene, hexagonal graphene onions, 3D seamless graphene-nanotube hybrid material which shows the requisite 7-membered rings at the interface junction, a top-down route to precisely patterned graphene nanoribbons that are sub 10-nm in width and microns long, and reinforced 2D graphene for increased mechanical performance. The use of graphene, graphene nanoribbons, and their derivatives in supercapacitors, interdigitated microsupercapacitors, field emitters and battery applications will be mentioned.
5:00 AM - *OO3.02
Synthesis and Assembly of Chemically Modified/Doped Graphitic Carbons for Optimized Nanostructures and Nanodevices
Sang Ouk Kim 1 2
1Korea Advanced Inst Sci amp; Tech Daejeon Republic of Korea2Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS) Daejeon Republic of KoreaShow Abstract
Graphitic carbon nanomaterials, including fullerene, carbon nanotubes and graphene, attract enormous research attention due to their outstanding material properties along with molecular scale dimension. The optimized utilization of those graphitic carbons in various optoelectronic and energy applications inevitably requires the molecular scale structure engineering as well as subtle controllability of material properties. In this regard, the chemical modification and substitutional doping of heteroatoms, such as Boron or Nitrogen, into the graphitic plane offers robust and reliable solution. In this presentation, our recent research achievements associated to tailored molecular scale assembly of chemically modified & doped graphitic carbon nanomaterials and their ultimate applications for various nanomaterials and nanodevices will be presented. In our approach, graphitic carbons can be efficiently processed into various three-dimensional structures via directed molecular assembly [see our invited feature article, Adv. Funct. Mater. 21, 1338 (2011)]. For instance, vertical carbon nanotube forest can be grown from graphene film surface to constitute three-dimensional carbon hybrid materials. Three-dimensional shape-engineered graphene gels can be spontaneously assembled at metal surfaces by electroless reduction of graphene oxide aqueous dispersion. Those molecular scale carbon assembled structures with extremely large surface and high electro-conductivity are potentially useful for catalysis, energy storage and so on. In addition, the substitutional doping of graphitic carbon with B- or N- was achieved via pre- or post-synthetic treatment. The resultant chemically modified graphitic carbons with tunable workfunction and remarkably enhanced surface activity could be employed for organic solar cells, organic light emitting diodes, nanocomposites, liquid crystalline materials, flexible substrate for nonplanar & flexible nanopatterned structures, nanocatalysts for improved functionalities and devices performances [see our recent invited review article, Adv. Mater. DOI: 10.1002/adma.201303265].
5:30 AM - OO3.03
Observing Graphene Grow: Complementary In-Situ XPS, XRD and ESEM Observations during Graphene CVD on Polycrystalline Cu Foils
Piran Ravichandran Kidambi 1 Bernhard C Bayer 1 Raoul Blume 2 Zhu-Jun Wang 2 Marc Willinger 2 Carsten Baehtz 3 Robert S Weatherup 1 Robert Schloegl 2 Stephan Hofmann 1
1University of Cambridge Cambridge United Kingdom2Fritz Haber Institute Berlin Germany3Forschungszentrum Dresden-Rossendorf Dresden GermanyShow Abstract
Despite the emergence of chemical vapor deposition (CVD) on polycrystalline Cu as the most widely used route to obtain high-quality, large-area graphene, the fundamental growth mechanisms, which are governed by the interaction between graphene and the catalyst during growth, remain largely unexplored.
Complementary in situ X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), and environmental scanning electron microscopy (ESEM) are used (at industrially relevant CVD conditions of pressure ~0.001-0.5 mbar and temperature ~900-1000oC for several hydrocarbon sources) to fingerprint the entire graphene chemical vapor deposition process on technologically important polycrystalline Cu catalysts to address the current lack of understanding.[1,2]
We note that graphene forms directly on metallic Cu during the high-temperature hydrocarbon exposure, whereby an upshift in the binding energies of the corresponding C1s XPS core level signatures is indicative of coupling between the Cu catalyst and the growing graphene. Postgrowth, ambient air exposure even at room temperature decouples the graphene from Cu by (reversible) oxygen intercalation. Further, we note that the coupling is also strongly affected by minor gaseous eg: oxygen contaminations, leading to a change in the graphene-Cu interaction during the growth process.Minor carbon uptake into Cu can under certain conditions manifest itself as carbon precipitation upon cooling. 
We compare the graphitic carbon growth mechanism for metal catalysts with a low solubility to novel oxide catalyst systems which inherently exhibit extremely low carbon solubility in an effort towards studying graphene growth directly on a dielectric  and highlight the importance of our complementary in-situ approach to study the growth of other 2D nanomaterials during CVD.
1. Kidambi et al. Nano Letters 13 (10), 4769-4778 (2013).
2. Kidambi et al. J. Phys.Chem. C. 116, 42, 22492-22501 (2012).
3. Kidambi et al. PSS RRL. 5, 9, 341-343 (2011).
OO1: Mechanical Properties
Monday AM, April 21, 2014
Moscone West, Level 2, Room 2008
11:30 AM - *OO1.01
Electronic-Mechanical Coupling in Graphene from in situ Nanoindentation Experiments and Multiscale Atomistic Simulations
Julia R Greer 1 Mingyuan Huang 1 Tod A Pascal 2 Hyungjun Kim 2 William A Goddard 1
1Caltech Pasadena USA2Korea Advanced Institute of Science and Technology Daejeon Republic of KoreaShow Abstract
Graphene&’s high electron mobility, scalability and excellent thermal conductivity make it a promising semiconductor candidate for post-CMOS electronic devices. We performed in situ nanoindentation to induce uniaxial tensile strain in suspended graphene devices and simultaneously measured electronic transport properties. We found Young&’s modulus to be sim;335 N/m, consistent with previous reports and our atomistic simulation results. Electrical measurements indicate the gauge factor of sim;1.9, comparable to the 2.4 predicted by simulations. Our transport measurements reveal that a moderate uniaxial strain is not capable of opening a band gap in graphene and does not affect its carrier mobility. This result matches our first principle-based MD simulations, as well as other theoretical predictions. The implications are that unlike for many other CMOS devices, mechanical strain, which can be easily controlled through device fabrication, is not an effective means to alter electronic transport properties in graphene.
12:00 PM - OO1.02
Understanding the Strength of Single Crystal and Polycrystalline Graphene
Haider Imad Rasool 1 2 3 Colin Ophus 5 William S Klug 4 6 Alex Zettl 1 2 7 James K Gimzewski 3 4 8
1UC Berkeley Berkeley USA2Lawrence Berkeley National Laboratory Berkeley USA3UCLA Los Angeles USA4UCLA Los Angeles USA5Lawrence Berkeley National Laborator Berkeley USA6UCLA Los Angeles USA7UC Berkeley Berkeley USA8National Institute for Materials Science Tsukuba JapanShow Abstract
The mechanical properties of materials depend strongly on their precise crystal structure and defect density. In our current work, we measure the yield strength of suspended single crystal and bicrystal graphene membranes prepared from chemical vapor deposition growth. Membranes of interest are characterized structurally by transmission electron microscopy and mechanically tested using atomic force microscopy. A single crystal diamond tip with a large indentation radius is used to measure the intrinsic strength of suspended membranes for mechanical measurements. Single crystal membranes prepared by chemical vapor deposition have strengths that are similar to previous results of single crystal membranes prepared by mechanical exfoliation. Bicrystal grain boundary membranes with large mismatch angles have higher strengths than their low angle counterparts. These large angle grain boundaries show strengths that are comparable to single crystal graphene. To further investigate this enhanced strength, we use aberration corrected high resolution transmission electron microscopy to explicitly map the atomic scale strain fields in suspended graphene. The enhanced strength of bicrystal membranes is attributed to the presence of low atomic-scale strain in the carbon-carbon bonds at the boundary.
12:15 PM - OO1.03
Evolution of Nanobubbles in Graphene Liquid Cells: An in-situ TEM Study
Dongha Shin 1 Jong Bo Park 1 Sang Jin Kim 1 Jin Hyoun Kang 1 Bora Lee 1 Sung-Pyo Cho 1 Byung Hee Hong 1
1Seoul National University Seoul Republic of KoreaShow Abstract
Water, which is most abundant in Earth surface and very closely related to all forms of living organisms, has a simple molecular structure but exhibits very unique physical and chemical properties. Even though tremendous effort has been paid to understand this nature&’s core substance, there amazingly still lefts much room for scientist to explore its novel behaviors. Especially, as the scale goes down to nano-regime, water shows extraordinary properties that are not observable in bulk state. One of such interesting features is the formation of nanoscale bubbles showing unusual long-term stability. Nanobubbles can be spontaneously formed in water on hydrophobic surface or by decompression of gas-saturated liquid. In addition, the nanobubbles can be generated during electrochemical reaction at normal hydrogen electrode (NHE), which possibly distorts the standard reducti