New features of the nano-scale structure of amorphous hydrogenated material, which had been produced by the implantation-induced amorphization of crystalline Si, were studied by using the small-angle X-ray scattering technique. The Si ion energies ranged up to 17MeV, and generated a thick (8) amorphous layer on a crystalline wafer. As-implanted and thermally annealed (up to 540C) amorphous hydrogenated samples were studied. No nano-voids were detected within a sensitivity of 0.1vol%, but the atomic-scale structure produced a measurable diffuse scattering signal that decreased with increasing annealing temperature. The measurements showed that the known density deficit of 1.8% in amorphous Si, relative to crystalline Si, could not be due to voids, and that the amorphous material was homogeneous at the nm scale.

D.L.Williamson, S.Roorda, M.Chicoine, R.Tabti, P.A.Stolk, S.Acco, F.W.Saris: Applied Physics Letters, 1995, 67[2], 226-8