![]() L'indice de réfraction complexe a été calculé en utilisant une méthode développée par les auteurs. ![]() ![]() Le matériel est considéré comme amorphe si les dimensions des cristallites, déterminées par diffraction des rayons X, sont inférieures à 20 Å.Pour les deux types de film, polycristallin et amorphe, on a mesuré les coefficients de réflexion et de transmission à incidence normale, pour l'intervalle de longueur d'onde 2600 Å < λ < 9000 Å. Les films polycristallins sont obtenus en utilisant des substrats chauffés, alors que les films amorphes sont déposés sur des substrats refroidis. Résuméĭes films de CdS, polycristallins et amorphes, ont été déposés sous vide sur des substrats de saphir fondu. The optical data are consistent with a model of an amorphous material which assumes that, at low photon energies, transitions take place from localized to extended states (or vice-versa) while at higher energies they also occur between extended states. In the amorphous material the absorption edge is shifted to lower energies and is no longer a direct transition as in the crystalline case, but is a nondirect transition. The amorphous material does not show this decrease at high energies because the grain size is much smaller. In this region, the crystalline films exhibit surface roughness due to the crystallite grains and hence cause the measured reflectivity and calculated index of refraction to be smaller than the bulk values. The polycrystalline results agree well with previous values except in the ultraviolet portion of the spectrum. The complex index of refraction has been calculated using a smooth curve thickness variation method developed by the authors. ![]() The material is considered to be amorphous if the crystallite size is smaller than 20 Å as determined by X-ray diffraction.Normal incidence reflection and transmission have been measured by the sample-in, sample-out technique over a range of wavelengths (2600 Å < λ < 9000 Å) for both polycrystalline and amorphous materials. The polycrystalline samples are obtained using heated substrates and the amorphous samples are grown on cooled substrates. Polycrystalline and amorphous films of CdS have been vacuum deposited onto fused sapphire substrates. ![]()
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