A study was made of the evolution of the structure of intrinsic and doped hydrogenated amorphous Si films exposed to a H plasma. For this purpose, in situ spectroscopic ellipsometry and secondary ion mass spectrometry measurements were combined. It was shown that H diffused faster in B-doped hydrogenated amorphous Si than in intrinsic samples, leading to a thicker sub-surface layer right from the early stages of H plasma exposure. At longer times, H plasma leads to the formation of a microcrystalline layer via chemical transport, but there was no evidence for crystallization of the a-Si:H substrate. Moreover, it was observed that, once the microcrystalline layer was formed, H diffused out of the sample.

Hydrogen Diffusion and Induced-Crystallization in Intrinsic and Doped Hydrogenated Amorphous Silicon Films. F.Kail, A.Hadjadj, P.Roca i Cabarrocas: Thin Solid Films, 2005, 487[1-2], 126-31

Figure 5

Diffusivity of H in Si

D (cm2/s) = 1.22 x 102 exp[-1.36(eV)/kT]