Growth direction control of InAs nanowires on (0Â 0Â 1) Si substrate with SiO2/Si nano-trench

We report on direction control of InAs nanowire (NW) grown on (0 0 1) Si substrate with SiO2/Si nanotrench. A two-step method was used to enhance the direction control. In the first step, we aligned the In beam with the longitudinal axis of the trench utilizing shadowing effect to nucleate InAs on only one trench end. In the second step, the growth proceeded with substrate rotation. Comparing with NW growths using only one step, either the first one or the second one, two-step growth demonstrates highly directional NWs. Transmission electron microscope (TEM) and one dimensional Fourier image analyses show that InAs NW can be easily grown from the (1¯11) Si residue, which was left at trench ends by fabrication process, due to the tiny residue volume and low V/III ratio. In contrast, InAs nucleus, located at the center of the trench, developed into island and cluster because of the high V/III ratio and large lattice mismatch.