▎ 摘　　要

The contact resistance (R-c) between graphene and metal electrodes is of crucial importance for achieving potentially high performances for graphene devices. However, previous analytical models based on Landauer's approach have failed to include the Fermi velocity difference between the graphene under the metal and the pure graphene channel. Hereby we report a theoretical model to estimate the Rc using density-functional theory and non-equilibrium Green's function methods. Our model not only presents a clear physical picture of the metal-graphene contacts, but also generates R-c values which are in good agreement with the experimental results: 210 Omega mu m for double-sided Pd contacts compared with 403 Omega mu m for single-sided Pd contact.