Effects of hydrogen on structural relaxation and defect evolution in amorphous silicon

Hydrogenation effects on the structural relaxation and defect evolution in amorphous silicon (a‐Si) prepared by ion implantation and evaporation have been investigated using Raman scattering spectroscopy and positron lifetime measurements. Bond angle deviation Δθ in nonhydrogenated a‐Si was significantly reduced due to 300 °C annealing in atomic hydrogen atmosphere. This indicates that the reduction in Δθ of hydrogenated amorphous silicon (a‐Si:H) is not only due to relaxation during the deposition process of a‐Si:H films as proposed by Jackson et al. [Philos. Mag. B 64, 611 (1991)] but also due to posthydrogenation of nonhydrogenated a‐Si. It was also found that agglomeration of vacancy‐type defects in evaporated a‐Si during 450 °C annealing is enhanced after posthydrogenation, while no remarkable enhancement can be seen in a‐Si prepared by ion implantation. © 1996 American Institute of Physics.