Electronic-structure studies of hydrogenated amorphous silicon films

We have made in situ photoemission measurements of a-Si prepared by dc sputtering in a mixture of H₂ and argon, and by reacting atomic hydrogen with sputtered films of a-Si. Differences in the hydrogen --- silicon bonding orbitals and the shift of the valence-band edge are discussed. Annealing experiments are presented which show the changes in electronic structure associated with the different silicon --- hydrogen complexes which evolve from the sample as the temperature is raised and the a-Si is dehydrogenated. The dominant changes in the electronic structure are attributed to single Si --- H bonds.