Crystallization of amorphous selenium films. II. Photo and impurity effects

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Abstract
Superposition of illumination with white light on thermal treatments of amorphous films, formed by deposition of high-purity Se on mica, had the following effects on crystallization: (i) interface cylindrites thickened much more rapidly but their radial growth rates were not detectably changed; (ii) the number density of interface cylindrites was sharply increased—this result may signify that the transition of single to cylindritic crystals, and not necessarily primary nucleation, is photoenhanced; (iii) surface cylindrites grew at much higher radial rates and developed a concentric ``hill-and-valley'' surface topology. The radial growth rates of interface cylindrites were reduced markedly by small amounts of certain impurities (e.g., Te or As) in the films and they are photoenchaned but not to the rates in the highest-purity films without illumination. In general, our results suggest that the primary effect of photoillumination on the crystal growth rates was to reduce the restraining action of impurities and mechanisms for this are considered.