▎ 摘　　要

An investigation has been conducted into the electron transport properties in carbon nanotube (CNT)-graphene contacts with a fully nonequilibrium Green's functions method combined with the density functional theory. Four different models are considered, where the contact geometries are varied. Their similar electron transmission characteristics are demonstrated with little dependence on the contact conditions at high energy and considerable dependence at low energy. The vacuum gap hinders the electron transport, resulting in an additional contact barrier. The electron transmission is mainly performed between the boundary carbon atoms of the CNT and the nearest graphene atoms, and the imperfection of the edge carbon atoms in a hexagonal lattice destroys the ballistic transport in graphene and the CNT at the contact. The current-voltage characteristics are presented as well. This reported work gives an insight into the electronic transport properties of the contacts and suggests that graphene is a suitable electrode material for applications in full-CNT devices.