Using coherent neutron scattering and secondary ion mass spectrometry techniques, it was found that atomic D which was introduced into amorphous hydrogenated material (from a plasma) diffused fast interstitially and replaced bonded H atoms. The effective diffusion coefficient was estimated to be about 10-14cm2/s. This was much larger than that for bond-breaking diffusion, which was equal to about 10-20cm2/s at 160C.

Fast Diffusion of Interstitial Deuterium in Amorphous Silicon. B.Abeles, L.Yang, D.Leta, C.Majkrzak: Journal of Non-Crystalline Solids, 1987, 97-98, 353-6