A Study of Bonding Configurations in Hydrogenated Amorphous Silicon

Si—H, Si—（H₂）—Si and Si—H—Si bonding configurations in a—Si:H were studied by ab initio （STO—3G） calculation and the results were compared with those of Johnson and Adler by using SCF—X_a—SW method. It is shown that hydrogenation compensates dangling bonds as well as strained bonds in a—Si and thus removes the undesirable electronic states in band gap. The strained defect in a—Si can plausibly be saturated by three center bonding of either hydrogen molecule or hydrogen atom with two silicon atoms in stretched state.