The growth of silica and silica-clad nanowires using a solid-state reaction mechanism on Ti, Ni andSiO2 layers

Abstract

A large area compatible and solid-state process for growing silica nanowires is reportedusing nickel, titanium and silicon dioxide layers on silicon. The silica nanowires alsocontain silicon, as indicated by Raman spectroscopy. The phonon confinementmodel is employed to measure the diameter of the Si rich tail for our samples.The measured Raman peak shift and full width at half-maximum variation withthe nanowire diameter qualitatively match with data available in the literature.We have investigated the effect of the seedbed structure on the nanowires, andthe effect of using different gas conditions in the growth stages. From this, wehave obtained the growth mechanism, and deduced the role of each individualsubstrate seedbed layer in the growth of the nanowires. We report a combined growthmechanism, where the growth is initiated by a solid–liquid–solid process, which is thenfollowed by a vapour–liquid–solid process. We also report on the formation of twodistinct structures of nanowires (type I and type II). The growth of these canbe controlled by the use of titanium in the seedbed. We also observe that thediameter of the nanowires exhibits an inverse relation with the catalyst thickness.