Energy level alignment of graphene oxide and its derivatives with ZnO

Abstract

Energy level alignment at the interface of ZnO with monolayer sheets of graphene oxide (GO), reduced graphene oxide (RGO), and simultaneously reduced and doped graphene oxide by ammonia plasma treatment (APGO) have been investigated using the photoelectron spectroscopy. The difference in surface sensitivity of XPS and UPS has been utilized to deduce the energy band diagram. The measurements reveal band bending, charge transfer and dipole formation at the interfaces. GO/ZnO and RGO/ZnO interfaces show dipole formation attributable primarily to interfacial charge transfer. In contrast, APGO/ZnO interface shows insignificant charge transfer and the energy level alignment being determined primarily by the doping of GO and ZnO and geometrical/structural changes in the later. The study facilitates improved understanding of the electronic structure of the interfaces of ZnO with GO and its derivatives and may be useful for designing efficient charge transport in such heterostructures.