Fabrication of Si nanocrystals in an amorphous SiC matrix by magnetron sputtering

2010-7
Si nanocrystals embedded in a wide bandgap material have been of interest for various electronic devices, including third-generation solar cells with efficiency values exceeding theoretical limits. In this work, Si-rich amorphous SiC layers with different Si contents were fabricated by the RF magnetron sputtering deposition technique. Si nanocrystal formation was induced by a high-temperature annealing process in a series of samples with different Si contents controlled by the DC power applied to the Si target during the sputtering. Nanocrystal formation was monitored to understand the basic kinetics as a function of process parameters, such as DC power and annealing temperature. In the SiC films containing excess Si, nanocrystal formation was clearly identified by Raman spectroscopy and high-resolution Transmission Electron Microscopy (TEM). Si nanocrystals with a mean size of 2 nm were imaged by TEM in the samples annealed at 1100 degrees C. The presence of Si-Si bonds was also detected by XPS through a series of experiments, including depth profiling of the chemical bonds of O, Si and C as a function of depth from the surface. Infrared spectroscopy was employed to study the stoichiometry of the SiC matrix with or without nanocrystals.