First-principles calculations have been used to investigate the structural and electronic properties of graphitic ZnO and MoS2(g-ZnO/MoS2)nanocomposites.It is found that the binding strength of g-ZnO/MoS2 exhibits strong dependence of atomic arrangement of g-ZnO relative to MoS2.The coupling interaction of g-ZnO/MoS2 obviously reduces the semiconducting band gaps,compared to both individual sheets,which are sensitive to its stacking orders.Interestingly,the vertical external electric field(E-field)can be applied to enhance the stability of g-ZnO/MoS2 and increase charge transfers between these two component.Furthermore,the E-field with the positive direction from MoS2 to g-ZnO can tune the band gap of g-ZnO/MoS2 nanocomposites,whereas this nanocomposites produce the semiconducting to metallic behavior transitions when the E-field changes from positive to negative direction,regardless of the stacking pattern.The tunable electronic properties of g-ZnO/MoS2 nanocomposites under the E-field are attributed to the changes in electrostatic potential difference between atom layer of MoS2 and interlayer region close to g-ZnO.Present results suggest that the g-ZnO/MoS2 heterojunction provides promising applications for MoS2-based optoelectronic and nanoelectronic devices,such as fabricating field effect transistor(FET).