Si nanocrystal-containing SiOx (x < 2) produced by thermal annealing of PECVD realized thin films

This paper is focused on the description of relationship between deposition parameters (flow rates of SiH4 and N2O precursor gases) and properties of SiOx films. The silicon-rich silicon oxide thin films deposited using plasma enhanced chemical vapour deposition (PECVD) in silane-nitrous oxide-helium discharges were thermally annealed at 1273 K for 1 h. Fourier transform infrared (FTIR) spectroscopy indicated that the chemical composition was dominated by silicon suboxide containing silicon-nitride and silicon-hydrogen bonds. For the as-deposited films and for the annealed films, Raman spectra show a band approximately at 480 cm−1, related to amorphous silicon and a band at 520 cm−1, related to nanocrystallite silicon, respectively. Transmission electron microscopy analysis demonstrated that silicon nanocrystals (Si nc), having a mean radius ranging between 3 and 6 nm were present in the annealed films. Using spectroscopic ellipsometry (SE) in the 0.2–0.88 μm spectral range, the values of layer thickness, optical indices and component volume fractions were determined using the Fourouhi–Bloomer (FB) model for the as-deposited films and the Bruggeman effective medium approximation (BEMA) for the annealed ones.