Effect of length and size of heterojunction on the transport properties of carbon-nanotube devices

By applying nonequilibrium Green's functions in combination with the density-functional theory, we investigate the electronic transport properties of molecular junctions constructed by the mirror symmetrical straight carbon-nanotube heterojunctions. The results show that the length and size of heterojunction play an important role in the electronic transport properties of these systems. The negative differential resistance behavior can be observed in such devices with certain length and size of heterojunction. A mechanism is suggested for the negative differential resistance behavior. (c) 2007 American Institute of Physics.