On demand shape-selective integration of individual vertical germanium nanowires on a Si(111) substrate via laser-localized heating.

Semiconductornanowire(NW)synthesismethodsby blanket furnace heating produce structures of uniform size and shape. This study overcomes this constraint by applying laser- localized synthesis on catalytic nanodots defined by electron beam lithography in order to accomplish site- and shape-selective direct integration of vertically oriented germanium nanowires (GeNWs) on a single Si(111) substrate. Since the laser-induced local temperature field drives the growth process, each NW could be synthesized with distinctly different geometric features. The NW shape was dialed on demand, ranging from cylindrical to hexagonal/irregular hexagonal pyramid. Finite difference time domain analysis supported the tunability of the light absorption and scattering spectra via controlling the GeNW shape.