Nature of long-range atomic H motion ina-Si:H

An infrared and secondary ion mass spectrometry study of H diffusion in undoped, rf-sputtered multilayered hydrogenated and deuterated amorphous silicon is reported. The results indicate that the long-range motion of atomic H is suppressed when the microvoid content exceeds a critical value associated with an initial ${\mathrm{SiH}}_2$ and ${\mathrm{SiH}}_3$ density $N_{d0}$≃7±1 at.%. The strong power-law time dependence of the diffusion constant (exponent α≃0.75±0.15) somewhat below this value of $N_{d0}$ is disucssed in relation to H migration mediated by mobile intrinsic defects, and the presence of an exponential distribution of traps for these defects and/or hydrogen.