X-RAY-DIFFRACTION STUDY OF THE EFFECT OF HYDROGEN-ATOMS ON THE SI-SI ATOMIC SHORT-RANGE ORDER IN AMORPHOUS SILICON

Evaporated a‐Si and glow discharge a‐Si–H samples are studied by X‐ray diffraction and the radial distribution functions are calculated. Special attention is given to the Fourier transform procedure in order to avoid non‐physical features in the critical interval between 4 and 6 Å. An important growth of a pair distance peak at 4.9 Å is observed for the hydrogenated material. This peak which corresponds to a 35° to 45° dihedral angle is attributed to the formation of seven membered Si rings or larger ones in the Si–H bond vicinity. The Si–Si first neighbour peak has an asymetrical shape likely due to the inhomogeneity of the material. The coordination number is found to be 3.5 instead of 4 for pure a‐Si. From this value a 33% H content is derived for the g.d. a‐Si–H sample which is deposited on a substrate hold at 25°C. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA