The effect of annealing temperature, residual O_2 partial pressure, and ambient flow rate on the growth of SiO_x nanowires

摘要

The active oxidation of a metal-coated Si substrate offers a convenient method to grow dense silica nanowire films directly on the substrate surface. In this study we investigate the effects of temperature and O_2 partial pressure in combination with different flow rates of the purging annealing gas. The flow rate is shown to have a direct effect on the onset of active oxidation and on the concentration and flux of monoxide vapor produced. Thicker nanowires are observed for increasing flow rates, while nanowire heights tend to decrease as predicted from simple velocity profile calculations. These results support the notion that the thicknesses of the nanowire films are determined by a critical monoxide vapor concentration above the substrate surface that can be readily modified by the flow rate of the purging gas.