Atomistic simulation of the load dependence of nanoscale friction on suspended and supported graphene

Suspended graphene exhibits distinct behavior in which nanoscale friction first increases and then decreases with load; this is in contrast to the monotonic increase of friction with load exhibited by most materials, including graphene supported by a substrate. In this work, these friction trends are reproduced for the first time using molecular dynamics simulations of a nanoscale probe scanning on suspended and supported graphene. The atomic-scale detail available in the simulations is used to correlate friction trends to the presence and size of a wrinkle on the graphene surface in front of the probe. The simulations also provide information about how frictional load dependence is affected by the size of the graphene, the size of the probe, and the strength of the interaction between graphene and probe.