Influence of the atmosphere on the growth by CVD of silicon based nanostructures

Silica nanowires (phi = 70-80 nm) and core crystalline silicon carbide/amorphous silica coaxial nanocables (phi = 30-50 nm) have been grown on Ni (5 nm) covered silicon substrates by thermal CVD at 950 degrees C. Heating the sample in different atmospheres and the addition of methane lead to the growth of the nanostructures. The as-grown product was characterized by Scanning Electron (SEM) and Transmission Electron (TEM) Microscopies, Infrared (IR) and Glow Discharge Optical Emission (GDOES) Spectroscopies. High contents of Ni, O and Si have been detected in the surface layer for argon and nitrogen treatments and in both cases silica based nanostructures grew. However, no nanostructures were obtained in hydrogen environment probably due to the detected Ni migration inward the substrate making the nanostructures nucleation more difficult. In this work we have studied and proven that previous processes on the substrate surface affect significantly the nanostructures growth.