  At a single atom thick, it is challenging to distinguish graphene from its
substrate using conventional techniques. In this paper we show that friction
force microscopy (FFM) is a simple and quick technique for identifying graphene
on a range of samples, from growth substrates to rough insulators. We show that
FFM is particularly effective for characterising graphene grown on copper where
it can correlate the graphene growth to the three-dimensional surface
topography and map the crystallographic orientation of the graphene
nondestructively, reproducibly and at high resolution. We expect FFM to be
similarly effective for studying graphene growth on other metal/locally
crystalline substrates, including SiC, and for studying growth of other
two-dimensional materials such as molybdenum disulphide and hexagonal boron
nitride.
