Investigation of electronic properties and chemical interactions of graphene- MoS x composites

Nanostructured transition metal dichalcogenide (TMDs) materials exhibit promising potential in next-generation optoelectronic devices and catalysts. TMDs possess chemically inert basal planes and catalytically active edge sites, with the relative population of the latter being a decisive factor for tailoring the structural, chemical and electronic properties of such nanostructures. In virtually all applications, TMD-based assemblies must be interfaced with other materials (such as graphitic domains in an electrode). During the in situ growth of MoS2 nanostructures in the presence of oxygen-doped graphitic materials, the formation of amorphous and/or crystalline Mo-based species could influence the chemical environment and electronic properties of the composites. In this study a detailed investigation of both graphene oxide (GO) and reduced graphene oxide (rGO) with MoSxOy composites were studied for the first time with X-ray and ultra-violet photoelectron spectroscopies (XPS/UPS). The composites were obtained upon gradual heating of GO and rGO with ammonium tetra-thiomolubdate (ATTM) hybrid films in Ultra High Vacuum where Mo6+, Moa+ (5 <= a < 6), MoS2 and sulphur oxides were formed. An accurate assessment of the chemical environment of the component interfaces along with its electronic properties was performed. These findings have implications for electronic transport and the understanding of behavior of such hybrid assemblies in many applications.