Structure, dissociation, and the vibrational signatures of hydrogen clusters in amorphous silicon

We use quantum molecular dynamics to study the structure, dissociation, and vibrational signatures of hydrogen clusters in amorphous silicon. Four structural models of hydrogenated amorphous silicon and two bulk $c$-Si:H structures are used for our study. We compare the properties of hydrogen clusters found in the structural models with other theoretical models and experimental measurements. By examining the energetics of H in these models, we gain insight into the trapping levels for H in $a$-Si:H films. In addition, we examine the geometric and vibrational properties of the hydrogen clusters as they dissociate. Our simulations are used to interpret the results of recent experiments including a low-temperature infrared study of hydrogenated amorphous silicon during light soaking.