Nanostructured ZnO films with various morphologies prepared by ultrasonic spray pyrolysis and its growing process

Nanostructured ZnO films were prepared by the ultrasonic spray pyrolysis method using Zn(CH3COO)(2)center dot 2H(2)O as a precursor. The effects of substrate temperature (T-s) on the morphology and properties were systematically studied. As the T-s increased from 430 degrees C to 610 degrees C, the morphology of the film transforms from closed packed nanosheets to dense nanocrystalline film and then to hexagonal nanorod array. The dense film formed at a temperature of 550 degrees C has the lowest electric resistivity and highest carrier concentration. The optical transmittance for all prepared samples was higher than 90%. The photoluminescence (PL) properties varied with the T-s due to the internal defect difference. The growth mechanism of ZnO film involves island growth and diffusion, which was evident by observing the samples prepared at various times. (C) 2013 Elsevier B.V. All rights reserved.