Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session V21: Focus Session: Graphene: Mechanical and Thermal Properties |
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Sponsoring Units: DMP Chair: Vitor Pereira, Boston University Room: Portland Ballroom 251 |
Thursday, March 18, 2010 8:00AM - 8:12AM |
V21.00001: Phonon lifetimes and thermal conductivity of graphene from first-principles Nicola Bonini, Jivtesh Garg, Nicola Marzari Carbon nanostructures, such as graphene and carbon nanotubes, are particularly promising materials for thermal management applications because of their very high thermal conductivity. A clear understanding of the transport properties of these materials is a key step in view of their possible integration into future devices. Here, we present a first-principles study of the thermal transport properties of graphene. We use density-functional theory and density-functional perturbation theory to determine both harmonic and cubic anharmonic terms in the crystalline potential---the key ingredients to calculate phonon frequencies and phonon lifetimes. Our results show that the long-wavelenght longitudinal and transverse in-plane acoustic phonon modes of graphene have an anomalously small lifetime, that leads to a significant underestimation of the thermal conductivity computed within the single mode relaxation time approximation. We will discuss the effect of strain and graphene-substrate interaction on the lifetime of the acoustic modes, and we will present results for the thermal conductivity determined by directly solving the linearized Boltzmann transport equation. [Preview Abstract] |
Thursday, March 18, 2010 8:12AM - 8:24AM |
V21.00002: Mechanical properties of graphene on deformable patterned substrates: Experimental studies S. Scharfenberg, C. Chialvo, D.Z. Rocklin, R. Weaver, P.M. Goldbart, N. Mason The mechanical properties of graphene can strongly influence its electronic behavior, and are relevant for implementing novel nano-mechanical devices. In this talk we present results on the mechanical behavior of few-layered graphene (FLG) placed on a patterned rubbery surface. Samples of FLG, with thicknesses ranging from 1-7 atomic layers, were deposited on micro-scale grooved polydimethylsiloxane (PDMS) substrates. AFM imaging techniques were then used to study the surface deformations, and to perform thickness measurements on the samples. AFM phase-imaging shows that the graphene strongly adheres to the substrate. The graphene also substantially deforms the substrate, with thicker pieces causing greater deformation. The results are discussed in the context of a linear elasticity theory (detailed in an accompanying paper) which can be used to explain the data and place bounds on the various interface strengths. [Preview Abstract] |
Thursday, March 18, 2010 8:24AM - 8:36AM |
V21.00003: Mechanical properties of graphene on deformable patterned substrates: Theoretical model D.Z. Rocklin, R. Weaver, S. Scharfenberg, C. Chialvo, N. Mason, P.M. Goldbart Recent experiments, reported in an accompanying paper, have addressed the consequences of depositing samples of few-layer graphene (FLG) on to a rubbery substrate patterned with microgrooves of amplitude $\sim $100~nm and wavelength $\sim $1~$\mu $m. The results of these experiments suggest that the graphene entirely adheres to the substrate, following the contour of its surface and causing a substantial flattening of the grooves (i.e., a reduction in the amplitude of the groove profile). We present a theoretical model based on linear elasticity theory that describes composite graphene-substrate systems. By analyzing the experimental data in terms of this model we are able to characterize the behavior of the FLG, and to place bounds on the adhesion strength between graphene and the polydimethylsiloxane substrate as well as on the shear strength between the layers of graphene. [Preview Abstract] |
Thursday, March 18, 2010 8:36AM - 9:12AM |
V21.00004: Graphene Mechanics and NEMS Invited Speaker: Graphene is an ideal material for nano-electromechanical devices (NEMS) due to properties such as high mobility, low density, and ultrahigh stiffness and strength. We have previously used nanoindentation to show that graphene has an ultimate strength of 130 GPa at an ultimate strain of over 25\%. We have also measured the elastic stiffness and strength of related materials, including hydrogenated graphene (graphane), BN, and MoS2. We have measured the resonant response of graphene NEMS using an electromechanical mixing technique. Toward development of applications, we have measured the response of the devices to changes in tension, mass, and temperature; the temperature-dependent resonant frequency can be used to measure the negative thermal expansion coefficient from 20 K to 300K. [Preview Abstract] |
Thursday, March 18, 2010 9:12AM - 9:24AM |
V21.00005: Graphene and Chemically Modified Graphene Nanomechanical Resonators Jeremy Robinson, Maxim Zalalutdniov, Jeffrey Baldwin, James Burgess, Zhongqing Wei, Paul Sheehan, Eric Snow, Brian Houston The facile synthesis of solution derived graphene and CVD graphene films have enabled recent advances in the large-area fabrication of graphene-based nanoelectromechanical structures. In this talk we describe routes to fabricate nanomechanical resonators and our characterization of the resulting structures. We find chemical modification has important consequences in the mechanical response of graphene-based resonators, including quality factor (Q) and Young's modulus (E). Graphene-based resonance structures are formed from both nominally pure graphene films and chemically modified graphene (CMG) formed from graphene oxide. Critically, a composite CMG/ graphene film facilitates the formation of high-quality, low-resistance resonators for incorporation into nanoelectromechanical systems. We further discuss chemical bonding of graphene versus CMG to the underlying substrate and its effect on subsequent quality factors of the resonator structures. [Preview Abstract] |
Thursday, March 18, 2010 9:24AM - 9:36AM |
V21.00006: Performance of graphene nanoelectromechanical resonators Changyao Chen, Sami Rosenblatt, Kirill Bolotin, William Kalb, Philip Kim, Ioannis Kymissis, Horst Stormer, Tony Heinz, James Hone Given the enormous stiffness and low mass density, graphene is an ideal candidate for nanoelectromechanical (NEMS) applications. Here, we demonstrate the fabrication and electrical integration of monolayer graphene resonators, and report their response to changes in mass and temperature. The resonant frequencies are in the megahertz range, and could be tuned by applied gate voltage. The quality factor increases with decreasing temperature, reaching 10,000 at 5~K. We also build a continuum mechanic model to understand the experimental data, which reveals the mass density and built-in strain of graphene, as well as its unusual negative thermal expansion coefficient. [Preview Abstract] |
Thursday, March 18, 2010 9:36AM - 9:48AM |
V21.00007: ABSTRACT WITHDRAWN |
Thursday, March 18, 2010 9:48AM - 10:00AM |
V21.00008: Electrical and optical detection of mechanical resonance in chemical vapor deposition grown single layer graphene membranes Arend van der Zande, Rob Barton, Phi Pham, William Whitney, Jeevak Parpia, Harold Craighead, Paul McEuen We fabricate large arrays of electrically contacted, suspended, single layer graphene membranes and measure the mechanical resonance electrically and optically. Large area single layer graphene is grown on copper foils using chemical vapor deposition. The graphene is transferred onto a silicon oxide surface, lithographically patterned into an array of electrically contacted rectangular sheets with varying lengths and widths between 300 nm and 5 um, and suspended using a buffered oxide etch. The graphene membranes can be actuated both electrically and optically, and the tension can be tuned electrostatically. Motion is detected using laser interferometry or electrical mixing. We examine the frequency, quality factor, and tuning of the graphene membranes as a function of their size and shape, and the temperature. [Preview Abstract] |
Thursday, March 18, 2010 10:00AM - 10:12AM |
V21.00009: Thermal Conductivity of Encased Graphene Wanyoung Jang, Zhen Chen, Wenzhong Bao, C.N. Lau, Chris Dames Understanding the thermal properties of graphene is important for the future graphene-based nanoelectronics, interconnects, and heat management structures, as well as fundamental physics. We use a ``heat spreader method'' to experimentally study the heat dissipation along graphene layers encased between two oxide layers and interpret the results by a 3-dimensional finite element method (FEM). The thermal conductivity of encased graphene layers is less than that of graphite, and increases with temperature and the number of layers. [Preview Abstract] |
Thursday, March 18, 2010 10:12AM - 10:24AM |
V21.00010: Lattice Thermal Conductivity of Graphene Suchismita Ghosh, Denis L. Nika, Evgenii P. Pokatilov, Irene Calizo, Alexander A. Balandin It was predicted by Klemens [1] that the lattice thermal conductivity of graphene should be higher than that of bulk graphite provided that graphene flake is large enough [1-2]. We have found an experimental confirmation to this prediction by measuring the thermal conductivity of the suspended graphene flakes [3-4]. We have also studied the evolution of the lattice properties as the number of graphene layers increases and developed the theory, which takes into account all allowed Umklapp scattering processes [5]. The superior thermal properties of graphene are beneficial for proposed electronic applications [6]. The work at UCR was supported by DARPA-SRC through FENA and IFC. [1] P.G. Klemens, J. Wide Band. Mat., 7, 332 (2000) [2] D.L. Nika, et al., Appl. Phys. Lett$.$, 94, 203103 (2009) [3] A.A. Balandin, et al., Nano Lett., 8, (2008) [4] S. Ghosh, et al., Appl. Phys. Lett., 92, (2008) [5] D.L. Nika, et al., Phys. Rev. B 79, 155413 (2009) [6] A.A. Balandin, IEEE Spectrum, 2009. [Preview Abstract] |
Thursday, March 18, 2010 10:24AM - 10:36AM |
V21.00011: Thermal conductance quantization in a T-junction Keivan Esfarjani, Natalio Mingo In this work, we have investigated transmission of phonons through a T-junction connecting a bulk material to a nanowire. This quantity determines the interface thermal conductance of the device and is relevant in the observation of the quantization of thermal conductance. The Green's function method is used to derive the frequency-dependence of the transmission coefficient calculated within Caroli et al's formalism. To get the frequency-dependence, we first adopt a simple nearest neighbor spring model and ca lculate the contribution of both linear acoustic and quadratic flexural modes of the wire, as well as the effect of the dimensionality of the bulk structure. More importantly, we also investigate the effect of the smoothness of the juntion on the transmission. It is found that 2D structures smoothly connected to the wire can have a finite transmission at low frequencies if their width is finite. This will lead to a quantization of thermal conductance but not necessarilty in integer multiples of the quantum of thermal conductance. Finally, results for a junction between bulk graphene and a graphene nanoribbon, using realistic force constants derived from first-principles density functional theory will be shown. [Preview Abstract] |
Thursday, March 18, 2010 10:36AM - 10:48AM |
V21.00012: Narrowband Nanomechanical Mass Spectrometry using Nonlinear Response of a Graphene Membrane Juan Atalaya, Andreas Isacsson, Jari Kinaret We propose a scheme for single-particle mass spectrometry using nonlinear response in 2D nanoresonators with degenerate eigenmodes. Using numerical and analytical calculations, we demonstrate that by driving a square graphene nanoresonator into the nonlinear regime, simultaneous determination of the mass and position of an added particle is possible. Moreover, in this scheme only measurements in a narrow band centered at the fundamental mode resonance frequency are needed. This avoids the need for measurements at different frequencies and makes feasible the realization of on-chip single-particle mass spectrometry. [Preview Abstract] |
Thursday, March 18, 2010 10:48AM - 11:00AM |
V21.00013: Current Saturation and Surface Polar Phonon Scattering in Graphene Vasili Perebeinos, Phaedon Avouris The electrostatic modulation of the graphene channel through gates yields very promising two-dimensional field-effect devices for analog and radio-frequency applications. Such devices should ideally be operated in the saturation limit. Our calculations suggest that in the diffusive regime surface polar scattering is the likely mechanism for the current saturation and that the observed full current saturation can only be accounted by the self-heating effect [1]. The currents can be enhanced if efficient device cooling is applied by appropriate choice of substrate and optimization of the graphene/substrate contact thermal resistance. \\[4pt] [1] V. Perebeinos and Ph. Avouris, ``Current Saturation and Surface Polar Phonon Scattering in Graphene'' arXiv:0910.4665. [Preview Abstract] |
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