Morphology of Thermally Evaporated Zinc Cleavage Surfaces

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Abstract
The process of thermal evaporation has been studied on (0001) cleaved zinc surfaces. The effects on the evaporated surface structures due to zinc vapor understauration, impurities, and crystal dislocations were investigated. For undersaturation ratios between 0.29 and 0.006, evaporation proceeded primarily from localized surface regions resulting in shallow conical evaporation pits. The number density of these evaporation pits was in good agreement with the dislocation density determined by chemical etching. It was concluded that the step sources responsible for the evaporation pits were dislocations terminating at the surfaces. The theory of evaporation from dislocation sites predicts a critical undersaturation similar to that observed experimentally. The interferometrically measured evaporation‐pit slopes increased with vapor undersaturation in agreement with the theory of Cabrera and Levine near the critical undersaturation. The data extended further into the region of higher undersaturations. The effects of surface impurities were studied by admiting oxygen into the evaporation cell. For a constant vapor undersaturation, the evaporation pit slopes increased at the higher oxygen pressures. This increase could be explained qualitatively as a result of adsorbed impurities.

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