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

Nanocrystalline silicon (nc-Si) films were prepared by a plasma-enhanced chemical vapor deposition method at a deposition temperature below 220 8C with different dynamic pressures (Pg), hydrogen flow rates ([H2]), and RF powers, using SiH4/H2/SiF4 mixtures. We examined the photoluminescence (PL) spectra and the structural properties. We observed two stronger and weaker PL spectra with a peak energies around EPL = 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 SiOrelated bonds. The nc-Si films with rather large PL intensity was obtained for high [H2] and/or low pressure values, However, effects of [H2] are likely to be different from those of Pg. The average grain size (d) and the crystalline volume fraction (r) at first rapidly increase, and then slowly increase, with increasing Pg. Other parameters exhibited opposite behaviors from those of d or r. These results were discussed in connection with the changes in the PL properties with varying the deposition conditions.