First-principles study of graphene adsorbed on WS2 monolayer

We perform first-principles calculations to study the energetics and electronic properties of graphene adsorbed on WS2 surface (G/WS2). We find that the graphene can be bound to WS2 monolayer with an interlayer spacing of about 3.9 angstrom with a binding energy of -21-32 meV per carbon atom dependent on graphene adsorption arrangement, suggesting a weak interaction between graphene and WS2. The nearly linear band dispersion character of graphene can be preserved in G/WS2 system, with a sizable band gap, depending on graphene stacking patterns on WS2 and the distance between graphene and WS2 monolayer. More interestingly, when the interlayer spacing is larger than 3.0 angstrom, the energy-gap opening is mainly determined by the distortion of the isolated graphene peeled from WS2 surface, independent on the WS2 substrate. Further tight-binding model analysis demonstrates that the origin of semiconducting properties can be well understood by the variation of on-site energy of graphene induced by WS2 substrate. (c) 2013 AIP Publishing LLC.