Surface hydride composition of plasma deposited hydrogenated amorphous silicon: in situ infrared study of ion flux and temperature dependence

The surface silicon hydride composition of plasma deposited hydrogenated amorphous silicon (a-Si:H) films has been investigated through surface sensitive in situ attenuated total reflection infrared spectroscopy. The fraction of SiHx (x=1,2,3) on the surface is reported for films deposited at substrate temperatures in the range 40–370 °C and a series decomposition reaction set in which higher hydrides decompose into lower hydrides (SiH3 → SiH2 → SiH) for increasing substrate temperature is proposed. Surface dangling bonds promote the decomposition reactions on a-Si:H as concluded from experiments in which the incident ion flux during deposition is enhanced. A comparison is made with results reported for hydrogenated crystalline silicon surfaces and the hydrogen coverage of the a-Si:H surface is discussed.