Fluorination Clusters on Graphene Resolved by Conductive AFM

Partially fluorinated graphene samples were studied by conductive AFM. The conductivity is found to be strongly non-uniform with low conductivity patches of about 10 nm. We interpret this observation as formation of low conducting clusters of fluorinated graphene separated by areas of pristine material. This is the first direct observation of clustering of covalently bonded impurities on graphene surface.