▎ 摘　　要

The first principles calculations based on self-consistent charge density functional tight-binding have performed to investigate the electronic properties and rectification behavior of the graphene step shape junctions with the different widths for both unsaturated and Hydrogen saturated. We have relaxed the junctions and calculated the I-V curve, transmission spectrum, density of states and rectification ratio. We found that by increasing the width of the one side of the junction, rectification occurred obviously and the rectification ratio increases from one for the 1-1 junction to about 2.92 for the 1-6 junction. Moreover, we observed that by saturating the junctions with Hydrogen atoms, the current decreases, and also the rectification ratio decreases to 0.72 for the saturated 1-6 junction.