Peeling off graphene from Co nanoparticle covered graphite in a scanning tunneling microscope

We demonstrate that graphene layers can be removed from atomically flat graphite terraces that are covered with deposited Co nanoparticles (NPs) using the tip of a scanning tunneling microscope. Peeling with monolayer resolution is achieved by scanning the NP covered graphite surface in close proximity. In this exfoliation process part of the lifted upper graphene layer is cut from this layer, while the surrounding part relaxes back to the underlying graphite surface. This gives rise to the appearance of spatially varying Moiré patterns and to a modified electronic interaction with the underlying graphite, which is probed by scanning tunneling spectroscopy. NP assisted exfoliation provides a promising route for preparation of (few-layer) graphene under ultra-high vacuum conditions, ideally suited for high resolution scanning tunneling microscopy and spectroscopy based experiments.