Characterization of graphene layers by Kelvin probe force microscopy and micro-Raman spectroscopy

This paper considers a synthesis of graphene flakes on the Ni surface by vacuum thermal treatment of the "sandwich" a-SiC/Ni multilayer deposited on silicon wafer by magnetron sputtering technique. Lateral size of graphene flake is estimated to be about hundreds of microns while thickness estimated by Raman scattering varied from one to few layers. Atom force microscopy (AFM) is not able to detect graphene flakes in regime of surface topology examination due to large roughness of Ni surface. Employment of scanning Kelvin probe force microscopy (SKPFM) demonstrates a correlation of surface potential and graphene flakes visible by optical microscopy. Moreover, the SKPFM allows to detect the graphene layer even in case of absence of optical contrast from single graphene layer on nickel surface. Using of KPFM the potential differences between Ni and graphene is determined.