Quantum confinement effects in CdTe nanostructured films prepared by the RF sputtering technique

Two kinds of CdTe nanostructured films were prepared by the RF sputtering technique. The first kind of film was composed of a mixture of CdTe and CdTeO3crystallites and was obtained from thermal annealing of amorphous oxygenated CdTe sputtered films. The second one constituted by low oxygen doped CdTe crystallites were deposited at a substrate temperature of 500 °C. The films were characterized by means of X-ray diffraction, optical absorption and Auger electron spectroscopy. The results show that the fundamental absorption edge of the films is shifted toward higher energy as a consequence of the small size of the CdTe crystallites, which constitute them. The absorption edge of the films versus CdTe crystallite radius relation is analyzed in terms of the models by Efros and Efros and by Kayanuma. Due to the discrepancies of the experimental data with these models, a numerical analysis made with a variational method was implemented. This method considers the different environment surrounding the CdTe crystallites in the two kinds of films studied.