Negative differential resistance and rectifying behaviors in phenalenyl molecular device with different contact geometries

The electronic transport properties in phenalenyl molecular device are studied by using nonequilibrium Green's functions in combination with the density-functional theory. The results show that the electronic transport properties are strongly dependent on the contact geometry. The negative differential resistance behavior with large peak to valley ratio is observed when the molecule contacts the Au electrodes through two second-nearest sites or one second-nearest site and one third-nearest site, while the rectifying performance is observed only when the molecule contacts the Au electrodes through one second-nearest site and one third-nearest site. The mechanisms are proposed for these phenomena.