POSITRON TRAPPING AT DIVACANCIES IN THIN POLYCRYSTALLINE CDTE-FILMS DEPOSITED ON GLASS

We have performed positron annihilation experiments on CdTe films grow n by vacuum evaporation at 220-degrees-C on both plain glass and indiu m-tin-oxide-coated glass substrates. By checking the linearity of the valence annihilation parameter S versus the core annihilation paramete r W we introduce a method to analyze the data which directly shows tha t the same vacancy defect can be present in all the films. By comparin g the core annihilation parameter at the defect to that at the V(Cd) v acancy we can identify this defect as the divacancy V(Cd)-V(Te). Its c oncentration in the films decreases from about 10(18) to less than 10( 16) cm-3 after annealing in air at 400-degrees-C for about 30 min. Chl orine doping seems to stabilize the divacancies.