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 t echnique. The first kind of film was composed of a mixture of CdTe and CdTe O3 crystallites and was obtained from thermal annealing of amorphous oxygen ated CdTe sputtered films. The second one constituted by low oxygen doped C dTe crystallites were deposited at a substrate temperature of 500 degrees C . The films were characterized by means of X-ray diffraction, optical absor ption and Auger electron spectroscopy. The results show that the fundamenta l absorption edge of the films is shifted toward higher energy as a consequ ence of the small size of the CdTe crystallites, which constitute them. The absorption edge of the films versus CdTe crystallite radius relation is an alyzed in terms of the models by Efros and Efros and by Kayanuma. Due to th e discrepancies of the experimental data with these models, a numerical ana lysis made with a variational method was implemented. This method considers the different environment surrounding the CdTe crystallites in the two kin ds of films studied. (C) 2000 Elsevier Science Ltd. All rights reserved.