▎ 摘　　要

In this study, structural and electronic properties of two-dimensional hybrid ZnO/graphene (ZnO/G) and ZnO/ graphene/graphene (ZnO/G/G) nanocomposites are investigated based on first-principles calculations. The calculation indicates that interlayers of the two nanocomposites exist typical van der Waals (vdW) weak interactions. The intrinsic electronic properties of ZnO and graphene monolayer are well-conserved, and the deposition on ZnO substrate opens a band gap of graphene at the Dirac point. When electric fields are applied, the ZnO/G nanocomposites exhibits semiconducting to metallic transition. The transition between Schottky and Ohmic contacts can be effectively implemented, accompanied by the conversion of p-type and n-type Schottky. Meanwhile, the projected density of states and work function of ZnO/G are deeply investigated to discuss the effects of orbital and charge transfer. Compared to ZnO/G, ZnO/G/G would overcome the lower Schottky barrier height (SBH) to form Ohmic contacts, indicating a higher sensitivity to electric field modulation. The formation of low-resistance Ohmic contact has important application for high-performance semiconductor devices.