Nanotech 2010

Modeling the Rippling of Graphene

M.J. B. Moura, R. Thompson-Flagg, M. Marder
University of Texas at Austin, US

Keywords: graphene, molecular dynamics, semi-empirical potential


Experiments found that free standing, single-layer graphene sheets display ripples. These ripples can change the electrical and mechanical properties of the graphene sheets. Using molecular dynamics and the MEAM semi-empirical potential we found that graphene can develop ripples as a consequence of adsorbed molecules sitting on random sites. It is common for graphene samples to be exposed to the environment, therefore adsorbing impurities such as water, OH, H, etc. The adsorbates cause the bonds between the carbon atoms to lengthen slightly. Static buckles then result from a mechanism similar to the one that leads to the buckling of leaves. Ripples caused by roughly 20% coverage of adsorbates are consistent with experimental observation. We show why this mechanism is more likely to explain ripples than are thermal fluctuations or the Mermin-Wagner theorem (previously invoked).
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