Vapor Phase Growth and Properties of Zinc Sulfide Single Crystals

Abstract

The growth of zinc sulfide single crystals by a sealed tube vapor phase method is described. In this system the parameters that are studied are the evaporation temperature, the temperature schedule during a run, the temperature gradient along the length of the tube, and, finally, the ambient pressure of H₂S in the tube. The resulting crystals are of a rodlike, distorted rodlike, or platelike habit, and the dominant habit, in any given run, is responsive to variations in the experimental parameters. An altogether different habit is observed in runs performed in a vacuum. The structure of the crystals varies from pure hexagonal to reversed cubic; most of the crystals exhibit stacking faults to various degrees. The structure is a function of the growth temperature. For crystals grown in an H₂S ambient, the mechanism proposed is an initial growth of a fine rod followed by a thickening of the rod and its possible subsequent development into a plate. The whisker growth is probably not a nucleation process and may proceed by a screw dislocation or stepped plane mechanism. The subsequent steps, as well as the growth of crystals in a vacuum are consistent with a surface nucleation mechanism.