The coherent X-ray scattering for momentum transfer, k, between 0·025 and 15·0 Å-1 has been measured for a series of sputtered amorphous Ge films prepared at various substrate temperatures, Ts, between 0 and 350°C. Differences in the radial distribution function (RDF) of films of different Ts have been determined by an accurate differential scattering technique. The small angle scattering (SAS) of the films is less than 100 electron units for k < 1 Å-1. From a combination of SAS, RDF and scanning electron microscope studies, it is concluded that an observed increase in film density with increasing Ts occurs through a reduction in the number of voids about 7 Å or less in diameter. No variation of bond length with Ts is found. With increasing Ts, there is an increase in first and second-neighbour coordination and a reduction in bond angle distortion. The rate of change of coordination, C, with density, ρ0, is found to be d ln C/d ln ρ0 = 0·6±0·2. Using a new, general theory of the dependence of the RDF on the dihedral angle distribution, P(θ), it is shown that with increasing Ts there is an increased probability of dihedral angles corresponding to the staggered configuration. For all films, the experimental RDF between r = 4·5 and 6·2 Å agrees with a nearly random P(θ) distribution. Comparison of experimental RDF's of crystalline and amorphous Ge indicates the static distortion of the first-neighbour bond length has a standard deviation of only about 0·04 Å.
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