Evaporation Mechanism of CdS Single Crystals. I. Surface Concentration and Temperature Dependence of the Evaporation Rate

Abstract

The vacuum-evaporation rate of CdS single-crystal c face has been measured in the temperature range 600°—860°C. The activation enthalpy and entropy have been derived from the data. The mechanism of the surface dissociation reaction which limits the vaporization, was studied by evaporating CdS in vapor beams of cadmium and sulfur. The rate of impingement of cadmium and sulfur on the CdS surface was varied over more than two orders of magnitude. For high sulfur flux, the RCdS≃RS2—½ dependence was established. The evaporation rate of CdS remained virtually independent of the cadmium impingement rate over the studied range. A detailed evaporation mechanism is presented.