GeO_x and SiO_x nanowires grown via the active oxidation of Ge and Si substrates

In this study, we show that the volatile monoxide species generated during the active oxidation of Ge and Si substrates can be utilized in the presence of Au catalytic nanoparticles to nucleate and grow GeO_x and SiO _x nanowires. A simple thermodynamic model is developed to ascertain the critical O₂ partial pressure as a function of temperature required for the active oxidation of Ge and Si substrates and is experimentally verified. The ideal conditions for uniform nanowire growth across the substrate are shown to be primarily dependent on the O₂ partial pressure, the annealing temperature and thicknesses of the surface oxide, and deposited Au. The role of a metastable surface oxide separating the active oxidation and NW nucleation processes is also discussed.