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 ´Å 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 ´Å, 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