Layers of hydrogenated amorphous material were prepared by ion implantation to various H concentrations. The implanted samples were characterized, by means of low-angle X-ray scattering, secondary-ion mass spectrometry, and infra-red spectroscopy, before and after annealing at temperatures of up to 550C. The evolution of the H concentration profiles and bonding configurations, together with the atomic and nanoscale structures of the films, indicated that the solubility limit of H in amorphous hydrogenated material was between 3 and 4at%. This limit was associated with the defect-related trap concentration. If H was introduced into the matrix at a concentration which was well above its solubility, the alloy was intrinsically unstable with respect to the formation of H complexes. Upon annealing at temperatures above 300C, the excess (above the solubility limit) H left the matrix and probably formed H2 molecules which accumulated in nanoscale H complexes.

S.Acco, D.L.Williamson, P.A.Stolk, F.W.Saris, M.J.Van den Boogaard, W.C.Sinke, W.E.Van der Weg, S.Roorda, P.C.Zalm: Physical Review B, 1996, 53[8], 4415-27