Etch pits and dislocations in cadmium sulphide crystals

A technique is described for producing dislocation etch pits on (0001), (0001) and {1010} growth faces of cadmium sulphide crystals. Methods are also described whereby the dislocations are decorated by precipitation of either gallium or copper. The strongest proof that the etch pits are formed where dislocation lines cut the free surfaces is provided by (1) the characteristic etch pattern formed after indentation; (2) the densities of etch pits in intersecting low-angle grain boundaries; and (3) the coincidence of etch pits and decorated lines. Various other observations support the main evidence. In conclusion, it is shown that the dislocation content can play an important part in determining some of the electrical properties of the crystals. In particular, copper is rendered ineffective as an acceptor by precipitation, and dislocations introduced in cadmium sulphide/chlorine crystals by plastic bending lead to the formation of acceptors.