Structural, optical and photoelectric properties of hydrogenated polymorphous silicon

We have studied structural, electrical, photoelectric and optical properties of two series of polymorphous silicon thin films deposited by PECVD with variation of silane and hydrogen gas mixture pressure and substrate temperature. The change of gas pressure did not affect substantially films´ Raman spectra, but resulted in changes of photoconductivity values and spectral dependencies of absorption coefficient measured by constant photocurrent method. Observed changes in films´ optical and photoelectric parameters are associated with the presence of Si nanocrystals in the film structure as revealed by TEM. Substrate temperature did not affect substantially polymorphous silicon films structure and properties in annealed state, but increasing of the substrate temperature led to a formation of the material with enhanced stability against photoinduced degradation. Electron paramagnetic resonance spectra of polymorphous silicon samples showed signal with g=1,998. Possible nature of the signal is discussed.