▎ 摘　　要

The formation of heterojunction within solid-state devices enables them with eventually high performances, but provides a challenge for material synthesis and device fabrication because strict conditions such as lattice match are needed. Herein, we show a facile method to fabricate a van der Waals (vdW) heterojunction between two-dimensional (2D) bismuth oxyselenide (Bi2O2Se) and graphene, during which the graphene is directly transferred to the Bi2O2Se and served as a low-contract-resistant electrode with small work function mismatch (similar to 50meV). As an optoelectronic device, the Bi2O2Se/graphene vdW heterojunction allows for the efficient sensing toward 1200-nm incident laser. Regarding the application of field-effect transistors (FETs), the short-channel (50nm) sample can be synthesized by utilizing these two 2D materials (ie, channel: Bi2O2Se; drain/source terminal: graphene) and the n-type characteristic can be observed with the accordant field modulation. It is confirmed that we show a simple way to prepare the vdW heterojunction which is aiming to the high-performance applications among optoelectronics and FETs.