Formation of an oxide surface layer and its influence on the growth of epitaxial silicon nanowires

It is established that, when growing Si nanowires in a H$_2$ flow that has not been additionally purified from residues of O$_2$ and water vapor, SiO$_2$ layers are formed on the crystal surface and growth substrate. The growth of Si nanowires is inhibited because of the presence of an oxide surface layer, and the crystals are characterized by strong morphological instability. The thermodynamic conditions for the formation of an oxide surface layer and its effect on the growth of Si nanowires are determined. At synthesis temperatures of 750–1400 K, Si nanowires are thermodynamically unstable in the gas phase containing any appreciably low O$_2$ concentrations, and Si should completely transform into an oxide under favorable kinetic conditions. The thermal dissociation and hydrogen reduction of SiO$_2$ under Si-nanowire growth conditions are practically unrealizable.