Effects on vibrational and electronic properties of removing hydrogen atoms in hydrogenated amorphous silicon

The effects of removing hydrogen atoms on the vibrational and the electronic properties of hydrogenated amorphous silicon (a-Si:H) have been investigated. Besides the missing vibrational modes associated with the removal of H atoms, the changes in the Si-dominated modes can be correlated to local distortions at the site of the Si whose neighboring H was removed. The dangling-bond states have an average energy at 0.2 eV above the top of the valence band, which is 0.5 eV smaller than the generally accepted value for the electronic level with g=2.0055. The range of interaction between the dangling-bond states is about equal to the second-neighbor distance (4 AìŠ). Comparison of the electronic states with and without the presence of the hydrogen atoms allows us to locate the Si-H bonding states at 5.0 and 7.5 eV below the top of the valence band. © 1988 The American Physical Society.