Evidence for structural relaxation in measurements of hydrogen diffusion in rf-sputtered boron-dopeda-Si:H

H diffusion in boron-doped rf-sputter-deposited hydrogenated amorphous Si (a-Si:H) was measured by secondary ion mass spectrometry profiles of deuterium in annealed a-Si:H/a-Si:(H,D)/a-Si:H multilayers. The exponent α=0.7±0.1 of the diffusion constant D(t) =${\mathit{D}}_{00}$(ωt${)}^{\mathrm{-}\mathrm{\alpha }}$ strongly decreases after annealing for ∼50 h at 180 °C and ∼35 h at 225 °C. It then increases to ∼0.8–1, i.e., the diffusion is nearly quenched, at longer annealing periods extending up to 1100 h. This behavior is believed to result from modifications in the microvoid system related to structural relaxation of the Si network.