Cubic to hexagonal phase transition in CdTe polycrystalline thin films by oxygen incorporation

Polycrystalline oxygenated cadmium telluride thin films, with oxygen contents ranging from 0 to 15 at%, were grown by the reactive radio frequency sputtering technique. The structure of samples was studied using X-ray diffraction. The energy band gaps of the samples were obtained from optical absorption measurements. It was found that the cubic crystalline structure of as-deposited samples changes to the crystalline hexagonal CdTe phase and then to an amorphous CdTe:O structure as the oxygen content was increased from 0 to 15 at %. Evidence of this phase transition was obtained from X-ray diffraction and optical absorption measurements. For the films with low oxygen content an increase in the interplanar distances was observed, yielding to a reduction of the band gap of the material. Samples containing hexagonal CdTe nanocrystals show larger energy band gaps, as compared with those having the cubic CdTe phase. Copyright (C) 1996 Published by Elsevier Science Ltd.