▎ 摘　　要

Spectroscopic ellipsometry combined with measurements of electrical characteristics and Kelvin probe force microscopy have been employed to investigate the interaction between graphene and a gold substrate, and the consequent changes of graphene's complex refractive index on gold. A strong blue shift, as much as 350 meV, of the prominent absorption peak (exciton-shifted M-point Van Hove singularity in the ultraviolet range) of graphene has been observed, with respect to the peak position for the sample on an insulating substrate where this peak was observed at about 4.55 eV. The results show that an interaction between graphene and a gold substrate can be characterized through the change of graphene's optical properties. In addition, the effects that a water layer trapped between graphene and gold during the transfer process has on the charge transfer between graphene and the gold substrate have been investigated. (C) 2015 AIP Publishing LLC.