Vanadium oxide assisted synthesis of networked silicon oxide nanowires and their growth dependence

Networked silicon oxide nanowires have been synthesized by VO2 -assisted chemical vapor deposition at 1000 C on silicon substrate without supplying any gaseous or liquid Si source. Systematic study on the nanowire growth has indicated that morphology and composition of the final products are sensitive to the catalyst components, reaction atmosphere and temperature. Compared to Au and VO2 as catalysts individually, co-catalysts of Au and VO2 play a critical role in the formation of networked SiO2 nanowires. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations indi- cate that the silicon oxide nanowires have smooth surfaces with uniform diameters of 30-100 nm, and their lengths reach several hundred micrometers. X-ray photoelectron spectroscopy (XPS) results reveal the atomic ratio of silicon to oxygen is about 1:2. Growth dependence of the networked nanowires on hydrogen and temperature is also discussed. Vapor-liquid-solid (VLS) process is proposed for the growth mechanism of the networked nanowires. It is also found that the growth mechanism of SiO2 nanowires by increasing the temperature up to 1200 C changes to vapor-solid (VS) processes since wire-like structures can be formed without any catalyst or H 2 gas introduced into the system.