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

摘要

Nanostructured ZnO films were prepared by the ultrasonic spray pyrolysis method using Zn(CH_3COO)_2·2H_2O 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℃ to 610℃, 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 ℃ 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.