Graphene and metal oxide (Nb2O5 and TiO2) interaction: Strain and surface transfer doping

Recently graphene and graphene-based hybrid materials have attracted much attention due to unique chemical and physical properties. To develop an appropriate understanding of the properties of these hybrid materials, it is necessary to address the material preparation and the structural and defect issues as well as their influence on the performance in a wide range of applications such as photovoltaics, catalysis, optoelectronics, nanoelectronics, energy and hydrogen storage. In this work we studied the interaction of monolayer graphene and graphene nanoplatelets with Nb2O5 and TiO2, by means of X ray photoelectron (XPS) and micro-Raman spectroscopies, Rutherford backscattering spectrometry (RBS). Both oxides were deposited by RF sputtering. In particular, the structural modification and strain induced in graphene during the layer deposition processes as well as the electron properties at the interface between graphene and the metal oxide were investigated. Raman analysis revealed the occurrence of both doping and strain in oxide-decorated graphene, while XPS analysis showed graphene doping evidenced by shifts of the Fermi level correlated with the oxide amount on graphene. The effect of hydrogenation of the Nb2O5-graphene hybrid material was studied as well, by means of RBS, elastic recoil detection analysis and XPS analyses, which showed an hydrogen uptake directly linked to the graphene decoration extent.