TEM, AFM, and Cathodoluminescence Characterization of CdTe Thin Films

The morphology, microstructure, and luminescent properties of polycrystalline CdTe films were investigated. The films were deposited by close-spaced sublimation at relatively low temperatures. The evolution of the film morphology and microstructure was studied as a function of deposition temperature and post-deposition heat treatment. Films deposited at low temperature exhibited fine, equiaxed grains. Dramatic grain growth was observed as a consequence of heat treatment. The film microstructure is heavily faulted and strongly dependent on the deposition and post-deposition treatment temperatures. The extended defects are mostly lamellar twins and stacking faults with similar densities. These defects often form a closely spaced arrangement, which leads to the formation of a local hexagonal phase. The presence of this hexagonal phase is expected to have significant effects on the electrical properties of the cubic CdTe films.