Electronic transport properties of a metal-semiconductor carbon nanotube heterojunction

We use a four-orbital-per-atom tight-binding model in order to investigate the transport properties of a metal-semiconductor carbon nanotube heterostructure. The metallic (armchair) and semiconducting (zigzag) parts of the system are attached via a pentagon and a heptagon defects. It is shown that the "left-right" asymmetry of the system readily results in an asymmetric current-voltage (I-V) characteristic, which is of interest in, e.g., nano-diode applications. Although introducing external dopants is one way to enhance the intrinsic asymmetric transport characteristic of the system, we show, by examining the effects of severe bendings, that mechanical deformation may be used to enhance the asymmetric transport and to manipulate the I-V characteristic in a controllable manner, so as to achieve a particularly desired transport characteristic.