Ageing effects at graphene/germanium interface

X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Raman spectroscopy and scanning tunnelling microscopy/spectroscopy (STM/STS) were used to study the effects of a long exposition to the air moisture of the interface between graphene and Ge (110) substrate. The single-layer graphene was grown by chemical vapour deposition (CVD) directly on Ge. The Raman and XPS results indicated that oxidation occurs slowly probably due to the diffusion of oxygen containing species through short-circuits like defects and grain boundaries present in the graphene sheet, as revealed by AFM and STM. In a long time-scale, the oxidation process resulted in a decoupling between graphene and germanium and a modification of the local density of states measured by STS.