Growth of silica nanowires in vacuum

Silica nanowires were grown on a Pt-coated Si substrate in flowing Ar, dynamic vacuum, and sealed vacuum tubes. The amount of oxygen in the reaction chamber or tubes directly influenced the composition and morphology of the nanowires. The formation of nanowires assisted by Pt can be explained by the VLS mechanism and active oxidation of silicon. In flowing Ar and dynamic vacuum, the dimensions of the nanowires increased with the partial pressure of oxygen. For nanowires grown in sealed tubes, the nanowires became much shorter which can be ascribed to the limited amount of residual oxygen in the tube. Therefore, the growth of silica nanowires is determined by a critical concentration of oxygen, below which the growth of nanowires is suspended.