Abstract
Graphene coatings have been shown to protect the underlying material from oxidation when exposed to different media. However, the passivating properties of graphene in air at room temperature, which corresponds to the operating conditions of many electronic devices, still remain unclear. In this work, we analyze the oxidation kinetics of graphene/Cu samples in air at room temperature for long periods of time (from 1 day to 113 days) using scanning electron microscopy, conductive atomic force microscopy and Auger electron microscopy, and we compare the results with those obtained for similar samples treated in H2O2. We observe that unlike the graphene sheets exposed to H2O2, in which the accumulation of oxygen at the graphene domain boundaries evolves in a very controlled and progressive way, the local oxidation of graphene in air happens in a disordered manner. In both cases the oxide hillocks formed at the graphene domain boundaries can propagate to the domains until reaching a limiting width and height. Our results demonstrate that the local oxidation of the underlying material along the domain boundaries can dramatically decrease the roughness, conductivity, mechanical resistance and frictional characteristics of the graphene sheet, which reduces the performance of the whole device.