CONVERSION OF CHEMICALLY DEPOSITED ZNS FILMS TO PHOTOCONDUCTING ZNO FILMS

The formation of photoconducting ZnO films from chemically deposited ZnS films by air annealing is reported. The ZnS to ZnO conversion was confirmed by x-ray diffraction (XRD) and optical studies of the films. As-deposited films exhibited very little dark conductivity and no photoconductivity. Air annealing of the films at about 400-degrees-C for at least 15 min converted them to ZnO films with higher dark conductivity and photoconductivity. Repeated deposition improved the dark conductivity of the as-deposited films and dark conductivity and photoconductivity of the annealed films. The value of the photo- to dark conductivity ratio depends on the annealing time and temperature. These characteristics of ZnO films may be exploited for their potential application in low-cost solar cells and photodetectors.