The influence of deposition parameters on the structure of nanocrystalline silicon

The structure, hydrogen content and bonding configurations of nanocrystalline silicon films produced by PECVD using hydrogen-diluted silane have been investigated by Raman and IR-spectroscopies. The film structure has been studied in relation to deposition parameters, such as gas dilution ratio, amount of water vapor in the initial gas, substrate temperature (Ts) and the substrate material. An analysis of Raman spectra has revealed in the films nanocrystallites embedded in amorphous matrix. The crystallite size (L) is in the range 3.6–5.7 nm. The volume fraction of crystallises (Xc) varies between 15% and 81%, depending on preparation conditions. Both L and Xc are primarily influenced by the presence of water vapor in the initial gas and the substrate material, while the effect of Ts is less pronounced. IR data show the presence of bound hydrogen with a total concentration varying between 3 and 13 at.%.