Positron annihilation studies of Si, a-Si, and a-Si:H using Doppler broadening techniques

Multiple S-parameter determinations performed for crystalline silicon (c-Si), hydrogenated amorphous silicon (a-Si, H), and evaporated amorphous silicon (a-Si) reveal a difference in the observed Doppler broadened positron annihilation γ-energy spectra. Compared to the S-parameter obtained for c-Si, a systematic increase in the S-parameter was noted for a-Si:H and a-Si, with a-Si exhibiting the largest value. A positive correlation between the number of unpaired electron spins (Nsub(S)) and the corresponding S-parameter implies an association between electronic defect states and lattice defect states