▎ 摘　　要

Graphene-metal (MGr) hybrid contacts have been broadly used to improve the contact properties of twodimensional (2D) electric devices. Since grain boundaries of graphene are inevitable, it is quite necessary to investigate how the grain boundaries affect the contact properties of graphene-metal interfaces. Herein, based on first-principles calculations, we comprehensively studied the contact properties of graphene with grain boundaries deposited on different transition metals substrates including Ni, Pd and Cu(1 1 1) slabs. Our calculations show that the grain boundaries always narrow and lower the tunneling barrier of the contacts, which will significantly increase the tunneling possibility of the carriers at the contacts. These results suggest a very convenient method to improve the performance of the graphene-based devices.