Controlling the Growth of Single Nanowires in a Nanowire Forest for near-Infrared Photodetection

Controlling one-dimension nanowire growth at single nanowire level is vital for building up multifunctional nanowire-based devices and getting insights into nanowire growth mechanisms. In this letter, we report the first control of single nanowire growth in a nanowire forest by touching a growing tungsten oxide nanowire with a nanoprobe inside an environmental scanning electron microscope. Compared with naturally growing nanowires, the touched nanowire exhibits an accelerated radial growth rate and decelerated axial growth rate, with the ratio of axial growth rate to radial growth rate decreasing by a magnitude of up to two orders. It is flexible to alternately accelerate and decelerate the growth rate of single nanowires via nanoprobe touching and detaching. The acceleration of the radial growth rate is attributed to the touching-induced local cooling of the touched nanowires and the consequent dominant vapor source deposition on the sidewall due to the reduced effective diffusion length of adatoms and the reduced equilibrium source vapor pressure. Our results represent the first controllable nanowire growth at single nanowire level and provide insights into the diffusion kinetics of nanowire growth. The as-grown nanowires exhibit potential applications in near-infrared photodetectors.