Influence of cooling rate on optical properties and electrical properties of nanorod ZnO films

ZnO films are prepared on Ag-coated glass substrates by wet chemical method at low temperature using Zn(NO3).6H2O and dimethylamine borane complex (DMAB). The structural, electrical and optical properties of ZnO films are investigated by X-ray diffraction, scanning electron microscope, four-point probe method and photoluminescence, respectively. The ZnO film deposited at 90 oC is the most compact films with a c-axis preferred orientation. The cooling rate affects the optical and electrical properties of ZnO films dramatically. The ZnO films cooled at -15 oC exhibit the lowest electrical resistivity of 0.525 Ω cm and the strongest photoluminescence in visible light. The increase of the conductivity and the enhancement of the photoluminescence are attributed to the increase of oxygen vacancies in the films.