Structural and photo-luminescence properties of nanocrystalline silicon films deposited at low temperature by plasma-enhanced chemical vapor deposition

Abstract

Nanocrystalline silicon (nc-Si) films were prepared by a plasma-enhanced chemical vapor deposition method at a deposition temperature below 220 °C with different dynamic pressures ( P g), hydrogen flow rates ([H 2]), and RF powers, using SiH 4/H 2/SiF 4 mixtures. We examined the photo-luminescence (PL) spectra and the structural properties. We observed two stronger and weaker PL spectra with a peak energies around E PL = 1.8 and 2.2–2.3 eV, respectively, suggesting that the first band was related to nanostructure in the films, and another band was associated with SiO-related bonds. The nc-Si films with rather large PL intensity was obtained for high [H 2] and/or low pressure values, However, effects of [H 2] are likely to be different from those of P g. The average grain size ( δ) and the crystalline volume fraction ( ρ) at first rapidly increase, and then slowly increase, with increasing P g. Other parameters exhibited opposite behaviors from those of δ or ρ. These results were discussed in connection with the changes in the PL properties with varying the deposition conditions.