Density improvement of silicon nanocrystals embedded in silicon carbide matrix deposited by hot-wire CVD

The thin films of silicon nanocrystals (Si-NC) embedded in silicon carbide (SiC) matrix (Si-NC:SiC) were developed by using hot-wire chemical vapor deposition (HWCVD) from silane (SiH4) and methane (CH4) mixture gases diluted by hydrogen (H2). This method avoids the co-precipitation of Si-NCs and SiC-NCs from a high-temperature annealing process. According to the classical theory of nucleation, this paper experimentally investigates the possibilities to increase the density of Si-NCs by optimizing two processing parameters (ratio of SiH4 to CH4 and working gas pressure). Using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR), we characterized the grain size, crystal volume fraction, topography and bond configurations of as-deposited films. The experimental results demonstrate that increasing the working gas pressure can lead to higher density of Si-NCs, while increasing the ratio of SiH4 to CH4 can only increase the grain size, which is consistent with the mechanism of nucleation and growth of Si-NCs. This method can be used to improve the density of Si-NCs embedded in SiC matrix deposited by CVD without high-temperature annealing process.