STRUCTURAL, ELECTRICAL AND OPTICAL-PROPERTIES OF ZINC-OXIDE PRODUCED BY OXIDATION OF ZINC THIN-FILMS

We have investigated the effects of oxidation temperature on the physi cal properties of polycrystalline zinc oxide thin films. Zinc thin fil ms are oxidized at different temperatures in air. We have found that i ncreasing the oxidation temperature deteriorates the preferred c-axis orientation. Also, increasing the oxidation temperature enlarges the c rystal size and increases the number of needle-shaped crystals on the surface of the ZnO samples. By increasing the oxidation temperature, m ore than zinc melting point, tensile stresses start to build up in the films. Also by increasing temperature, sheet resistance of the films decreases, while photoluminescence intensity ratio (green to orange) i ncreases. Increasing the oxidation temperature reduces the transparenc y of the films, too. It is proposed that either an increase in the num ber of oxygen vacancies or a decrease in the volume of grain boundarie s, is responsible for the observed behavior of the films at higher oxi dation temperatures.