▎ 摘　　要

To understand the effect of grain boundaries (GBs) on the electronic transport properties of graphene, we have performed first principles studies on the electronic structure and transport properties of graphene with four single GBs and two crossed GBs. Calculations indicate that the zero band gap nature of graphene is not destroyed by introducing GBs. The localized states introduced by GBs have a positive contribution to the transport ability in the vicinity of the Fermi level. The transport properties across and along the GBs show an obvious discrepancy. Compared with the pristine graphene, an at least 50% current suppression is found in the transport across the GBs, while less current degradation is present along the GBs. The transport along other directions shows that the transmission ability can be efficiently enhanced by avoiding the transport direction across the GBs. Moreover, the transport behavior of the crossed GB is akin to that of the transport across a single GB.