Investigation of polycrystalline CdTe thin films deposited by physical vapor deposition, close-spaced sublimation, and sputtering

CdTe thin films, deposited on different substrate structures by physical vapor deposition, sputtering, and close-spaced sublimation, have been treated with CdCl2 at several temperatures. The morphology of the films has been studied by atomic force microscopy, and the observations were correlated to results obtained from x-ray diffraction, cathodoluminescence, and minority-carrier lifetime measurements. The samples treated at 400 °C resulted in the best device-quality films, independent of deposition method and underlying substrate structure. For the first time, a nanograin structure was observed in CdTe sputtered samples.