EFFECT OF SUBSTRATE TEMPERATURE AND POST DEPOSITED ANNEALING ON THE ELECTRICAL AND PHOTOLUMINESCENCE CHARACTERISTICS OF ZINC OXIDE FILMS DEPOSITED BY SPRAY PYROLYSIS

Zinc oxide (ZnO) films were deposited on heated glass substrates at different substrate temperatures by spray pyrolysis. The variation of sheet resistance of the films with substrate temperature and post deposited annealing in air and in vacuum, revealed the role of oxygen vacancy (V-O) in unintentional n-type conductivity of ZnO films. Photoluminescence (PL) characterization of the films revealed that there is strong reemission at 3.35 eV for the film deposited 500 degrees C and is much intense compared to defect related visible luminescence. The film deposited at substrate temperature 200 degrees C has a defect related emission centered at similar to 1.93 eV and that at 500 0C showed emission centered similar to 2.42 eV. Considering the theoretical suggestions and the variation of visible luminescence intensity and peaks with substrate temperature and post deposited annealing in air and in vacuum, it has been suggested that emission similar to 1.93 eV is caused by singly ionized oxygen vacancy (V-O(+)) and zinc vacancy (V-Zn) may be responsible for the emission at similar to 2.42 eV.