Guiding vapor-liquid-solid nanowire growth using SiO2.

Vapor-liquid-solid (VLS) grown nanowires (NWs) typically grow in [Formula: see text] directions. In this work, using guiding structures, we effectively grow Si NWs with diameters between 20 and 100 nm in both [001] and <110> directions by guiding the Si NW growth using SiO(2) surfaces. Using one structure, we demonstrate NW growth in the substrate plane, against the buried oxide layer of a standard, (001) silicon-on-insulator wafer. Using the other structure, we demonstrate NW growth perpendicular to a (001) substrate. We show that the VLS growth mechanism is the same as unconstrained NW growth, with the NWs still growing by the addition of {111} planes. We show that when the guiding surface is removed, the NW grows in its natural growth direction because the growth mechanism has not changed. We speculate that NW growth can be guided with a range of materials, the most suitable being those that are amorphous and those which are nearly immiscible both with the catalyst and with the NW material.