Influence of hydrogen dilution on bonding configurations and optical absorption properties of a-Si/SiNx composite films

Abstract

Infrared absorption and optical transmission combined with the optical absorption model have been used to study the influence of hydrogen dilution on bonding configurations and optical absorption properties of nano-sized amorphous silicon embedded in silicon nitride thin films (a-Si /SiNx). The amount of bonded hydrogen was investigated by the N-H and Si-H infrared absorption bands. The optical band gap and sub-gap absorption coefficient were obtained by optical absorption spectra. It is shown that the film deposited at 20 sccm hydrogen flow rate, which contains the highest bonded hydrogen content, has the maximum optical band gap and the lowest density of defects. Furthermore, the optical band gap and mean size of a-Si nano-grains in SiNx matrix were obtained through simulating the optical absorption data using an optical absorption model. The simulated optical band gap was in good agreement with the experiment results. These results suggest that appropriate hydrogen dilution in the precursor is beneficial to improving the microstructure and optical properties of the a-Si /SiNx composite films.