Strain-Enhanced Transverse Electron Transport in Few-Layer Graphene

Transverse electron transport in strained few-layer graphene samples was investigated through experimental and theoretical methods revealing highly localized behavior. A conductive atomic force microscopy (AFM) study was performed, where a local compressive force was applied to few-layer graphene samples. A change in the electrical resistance by several orders of magnitude was observed with increasing force. This response is shown to be largely invariant with the sample area, which is always much larger than the probe area, but dependent on the number of graphene layers comprising the sample. The drastic change in measured resistance with increasing compressive force cannot be attributed to a reduction in probe-sample contact resistance only. Instead, molecular modeling reveals that the application of force by the AFM probe creates highly strained regions within the few-layer graphene sample, resulting in a localized enhancement in electron transport in the out-of-plane direction. These results are explained through an interlayer electron tunneling mechanism that is highly sensitive to interlayer separation distance.