CUBIC TO HEXAGONAL PHASE-TRANSITION IN CDTE POLYCRYSTALLINE THIN-FILMS BY OXYGEN INCORPORATION

Polycrystalline oxygenated cadmium telluride thin films, with oxygen c ontents ranging from 0 to 15 at%, were grown by the reactive radio fre quency sputtering technique. The structure of samples was studied usin g X-ray diffraction. The energy band gaps of the samples were obtained from optical absorption measurements. It was found that the cubic cry stalline 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 th e interplanar distances was observed, yielding to a reduction of the b and gap of the material. Samples containing hexagonal CdTe nanocrystal s show larger energy band gaps, as compared with those having the cubi c CdTe phase. Copyright (C) 1996 Published by Elsevier Science Ltd.