Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session D1: Focus Session: Graphene - Mechanics and Strain |
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Sponsoring Units: DMP Chair: Phillip First, Georgia Institute of Technology Room: 001A |
Monday, March 2, 2015 2:30PM - 2:42PM |
D1.00001: Strain-Engineering of Giant Pseudo-Magnetic Fields in Graphene/Boron Nitride (BN) Periodic Nanostructures Chen-Chih Hsu, Jiaqing Wang, Marcus Teague, Chien-Chang Chen, Nai-Chang Yeh Ideal graphene is strain-free whereas non-trivial strain can induce pseudo-magnetic fields as predicted theoretically and manifested experimentally. Here we employ nearly strain-free single-domain graphene, grown by plasma-enhanced chemical vapor deposition (PECVD) at low temperatures, to induce controlled strain by placing the PECVD-graphene on substrates containing engineered nanostructures. We fabricate periodic pyramid nanostructures (typically 100 $\sim$ 200 nm laterally and 10 $\sim$ 60 nm in height) on Si substrates by focused ion beam, and determine the topography of these nanostructures using atomic force microscopy and scanning electron microscopy after we transferred monolayer h-BN followed by PECVD-graphene onto these substrates. We find both layers conform well to the nanostructures so that we can control the size, arrangement, separation, and shape of the nanostructures to generate desirable pseudo-magnetic fields. We also employ molecular dynamics simulation to determine the displacement of carbon atoms under a given nanostructure. The pseudo-magnetic field thus obtained is $\sim$150T in the center, relatively homogeneous over 50{\%} of the area, and drops off precipitously near the edge. These findings are extended to arrays of nanostructures and compared with topographic and spectroscopic studies by STM. [Preview Abstract] |
Monday, March 2, 2015 2:42PM - 2:54PM |
D1.00002: ABSTRACT WITHDRAWN |
Monday, March 2, 2015 2:54PM - 3:06PM |
D1.00003: Strain variation in corrugated graphene Xuanye Wang, Khwanchai Tantiwanichapan, Jason Christopher, Roberto Paiella, Anna Swan Raman spectroscopy is a powerful non-destructive technique for analyzing strain in graphene. Recently there has been interest in making corrugated graphene devices with varying spatial wavelengths $\Lambda$ for plasmonic and THz applications. Transferring graphene onto corrugated substrates introduces strain, which if there was perfect clamping (high fraction) would cause a periodic strain variation. However, the strain variation for pattern size smaller than the diffraction limit $\lambda$ makes it hard to precisely model the strain distribution. Here we present a detailed study on how strain varies in corrugated graphene with sub-diffraction limit periodicity $\Lambda$$<$$\lambda$. Mechanically exfoliated graphene was deposited onto sinusoidal shape silicon dioxide gratings with $\Lambda$=400 nm period using the pick and place transfer technique. We observed that the graphene is not rigidly clamped, but partially slides to relieve the strain. We model the linewidth variation to extract the local strain variation as well as the sliding in the presence of charge puddling in graphene. The method gives us a better understanding on graphene slippage and strain distribution in graphene on a corrugated substrate with sub-diffraction limit spatial period. [Preview Abstract] |
Monday, March 2, 2015 3:06PM - 3:18PM |
D1.00004: ABSTRACT WITHDRAWN |
Monday, March 2, 2015 3:18PM - 3:30PM |
D1.00005: Mechanical Properties of 1D Nanoscale Features in 2D Material Systems Mohsen Nasseri, Mathias J. Boland, Armin Ansary, D. Patrick Hunley, Douglas R. Strachan Two dimensional materials, such as graphene and MoS$_{\mathrm{2}}$, and hybrid structure of these materials have been studied extensively in the past few years because of their unique physical, mechanical, chemical and optical properties. Through the use of lateral force scanning probe manipulation and measurements, frictional, adhesive, and elastic characteristics of one-dimensional features of graphene and MoS$_{\mathrm{2}}$ are investigated. These include the local elastic strain and friction at the edges of these 2D materials. Evidence of elastic straining of graphene and MoS$_{\mathrm{2}}$ edges indicates that they behave as nanoscale springs. Estimates of the strain energy are consistent with out-of-plane bending of the edges and could represent a possible route for reversibly tuning the local electronic properties of these 2D materials. Unique mechanical properties of other 1D features, such as nanotubes, integrated with these 2D materials are also investigated. Such lateral force measurements reveal surprising nanometer-scale properties not apparent through other scanning probe investigations. [Preview Abstract] |
Monday, March 2, 2015 3:30PM - 3:42PM |
D1.00006: Elastic coupling between the layers in 2D films Yang Gao, Si Zhou, Suenne Kim, Hsian-Chih Chiu, Daniel N\'elias, Claire Berger, Walt de Heer, Roman Sordan, Laura Polloni, Angelo Bongiorno, Elisa Riedo Two-dimensional (2D) materials, such as graphene and graphene oxide, are a few-atomic-layer thick films with strong in-plane bonds and much weaker inter-layer interactions. While their in-plane elasticity has been widely studied in bending experiments where a suspended film is largely deformed, very little is known about their elastic modulus perpendicular to the planes. Investigations of the out-of-plane elasticity require indenting supported 2D films less than their interlayer distance. Here, we report on sub-{\AA}-resolution indentation measurements of the perpendicular elasticity of 2D materials. Experiments, combined with semi-analytical models and density functional theory are used to study the perpendicular elasticity of a few-layers thick graphene and graphene oxide films. Interestingly, we find that the graphene oxide perpendicular Young's modulus reaches a maximum when one complete water layer is intercalated between the graphitic planes then the perpendicular Young's modulus decreases because a second water layer starts to form in between the layers further swelling and softening the GO structure. [Preview Abstract] |
Monday, March 2, 2015 3:42PM - 3:54PM |
D1.00007: Nanoscale measurements of adhesion properties of graphene by nanoindentation Ji Won Suk, Seung Ryul Na, Rodney Ruoff, Kenneth Liechti The outstanding fundamental properties of graphene have enabled the realization of various applications including nanoelectronics and flexible devices. Measurement of interfacial properties is crucial for practical and reliable applications of graphene. In this talk, we report measurements of adhesion properties of large-area graphene transferred onto silicon oxide. Using a high sensitive nanoindentation tool, we observed nonlinear adhesive interactions of graphene with an indenter. The nanoscale measurements also provided interesting local behaviors of graphene related to wettability. The experimental results were analyzed with numerical simulation for further understanding. [Preview Abstract] |
Monday, March 2, 2015 3:54PM - 4:06PM |
D1.00008: Tracking the exact vertical movement of freestanding graphene Pijush Ghosh, Josh Thompson, Paul Thibado, Mehdi Neek-Amal, Francois Peeters Intrinsic ripples in freestanding graphene have, unsurprisingly, been exceedingly difficult to study with common experimental methods. In notable breakthroughs, individual ripple geometry was recently imaged using transmission electron microscopy as well as scanning tunneling microscopy, but these measurements are thus far limited to static graphene configurations. Thermally-activated flexural phonon modes could generate dynamic changes in curvature which would be of great interest to observe. Here, we present how to track the exact vertical movement of a one-square-angstrom region of freestanding graphene using scanning tunneling microscopy. This allows a direct measurement of the out-of-plane time trajectory and fluctuations at one point in space over long periods of time. Based on these data, we also present a model from elasticity theory to explain the unusual very-low frequency oscillations that are observed. Unexpectedly, we sometimes detect a sudden colossal jump, which we interpret as due to mirror buckling. This innovative technique provides a much needed atomic-scale probe for the time-dependent behaviors of intrinsic ripples in freestanding graphene. [Preview Abstract] |
Monday, March 2, 2015 4:06PM - 4:18PM |
D1.00009: Role of defects and geometry in the strength of polycrystalline graphene Zhigong Song, Zhiping Xu Defects in solids commonly limit mechanical performance of materials by reducing their rigidity and strength. In two-dimensional crystals, however, we report in this work that topological defects induce a prominent geometrical effect in addition to local stress buildup. These dual roles of defects modulate both local and global mechanical properties of the material in an unexpected way. We demonstrate through atomistic simulations and theoretical analysis that in some cases local response of two-dimensional crystals can even be stiffened and strengthened by topological defects. These new findings not only shed lights on mechanical characterization of two-dimensional materials, but also add a new dimension to material design, in the scenario of geometrical and topological engineering. \\[4pt] [1] Z. Song, J. Wu, Z. Xu, http://arxiv.org/abs/1402.1006v1.\\[0pt] [2] Z. Song and Z. Xu, Journal of Applied Mechanics 81, 091004 (2014).\\[0pt] [3] Z. Song, V. I. Artyukhov, B. I. Yakobson, and Z. Xu, Nano Letters 13, 1829 (2013).\\[0pt] [4] Z. Song, Z. Xu, X. Huang, J.-Y. Kim, and Q. Zheng, Journal of Applied Mechanics 80, 040911 (2013). [Preview Abstract] |
Monday, March 2, 2015 4:18PM - 4:54PM |
D1.00010: Basal-plane dislocations in bilayer graphene - Peculiarities in a quasi-2D material Invited Speaker: Benjamin Butz Dislocations represent one of the most fascinating and fundamental concepts in materials science. First and foremost, they are the main carriers of plastic deformation in crystalline materials. Furthermore, they can strongly alter the local electronic or optical properties of semiconductors and ionic crystals. In layered crystals like graphite dislocation movement is restricted to the basal plane. Thus, those basal-plane dislocations cannot escape enabling their confinement in between only two atomic layers of the material. So-called bilayer graphene is the thinnest imaginable quasi-2D crystal to explore the nature and behavior of dislocations under such extreme boundary conditions. Robust graphene membranes derived from epitaxial graphene on SiC provide an ideal platform for their investigation. The presentation will give an insight in the direct observation of basal-plane partial dislocations by transmission electron microscopy and their detailed investigation by diffraction contrast analysis and atomistic simulations. The investigation reveals striking size effects. First, the absence of stacking fault energy, a unique property of bilayer graphene, leads to a characteristic dislocation pattern, which corresponds to an alternating AB $\leftrightarrow $ BA change of the stacking order. Most importantly, our experiments in combination with atomistic simulations reveal a pronounced buckling of the bilayer graphene membrane, which directly results from accommodation of strain. In fact, the buckling completely changes the strain state of the bilayer graphene and is of key importance for its electronic/spin transport properties. Due to the high degree of disorder in our quasi-2D material it is one of the very few examples for a perfect linear magnetoresistance, i.e. the linear dependency of the in-plane electrical resistance on a magnetic field applied perpendicular to the graphene sheet up to field strengths of more than 60 T. [Preview Abstract] |
Monday, March 2, 2015 4:54PM - 5:06PM |
D1.00011: Strain and defect induced enhancement of Young's modulus of graphene Guillermo Lopez-Polin, Cristina Gomez-Navarro, Miriam Jaafar, Julio Gomez-Herrero, Vincenzo Parente, Rafael Roldan, Mikhail Katsnelson, Francesc Perez Murano, Francisco Guinea Graphene, due to its extremely high in plane stiffness and low bending rigidity, presents important out of plane thermal fluctuations crucial for the understanding of its mechanical properties. In this work we measure the variation of the stiffness of graphene with induced vacancy density using AFM nanoindentations. Unlike predicted, we find that the stiffness of graphene increases with defect content until a vacancy density of 0.2 percent, where it doubles its initial value. For higher defect density the elastic modulus exhibits a decreasing tendency. We attribute the initial increase in stiffness to the quenching of the out of plane oscillations of graphene due to defects [1]. In order to validate this interpretation we also study the dependence of the elastic modulus with strain. We observe an increase of the Young's modulus at pre-strains higher than 0.5 percent where it again doubles its initial value. \\[4pt] [1] Nature Physics accepted. [Preview Abstract] |
Monday, March 2, 2015 5:06PM - 5:18PM |
D1.00012: Irradiation-Induced Superplasticity of Graphene and Carbon Nanotubes Zhuhua Zhang, Yu Lin, Feng Ding, Boris I. Yakobson The superplasticity of carbon nanotubes has been related to the dynamics of pentagon-heptagon (5\textbar 7) dislocations, but the mechanism remains elusive in light of prohibitively high barrier ($\sim$ 7 eV) of dislocation migration [1,2]. Here, we reveal the key role of electron irradiation in facilitating the dislocation migration and promoting nanotube plasticity. Atomistic simulations show that irradiation-induced adatoms and monovacancies diffuse towards the sessile 5\textbar 7 dislocations and switch them into a mobile radical state with a migration barrier as low as 1.6 eV, thereby significantly enhancing the plastic flow. The radical dislocations also act as defect scavengers to prevent lattice disorder in the tube wall, in agreement with experimental phenomena. Further, a formula is derived to quantify the plasticity in terms of irradiation intensity, aimed to guide the irradiation engineering of plasticity of carbon nanomaterials. \\[4pt] [1] F. Ding, K. Jiao, M. Wu, and B.I. Yakobson, Phys. Rev. Lett., 98, 075503 (2007).\\[0pt] [2] F. Ding, K. Jiao, Y. Lin, and B.I. Yakobson, Nano Letters 7, 681-684 (2007). [Preview Abstract] |
Monday, March 2, 2015 5:18PM - 5:30PM |
D1.00013: ABSTRACT WITHDRAWN |
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