Effects of Annealing on Chemical Composition, Crystallinity, Optical Transmission and Electrical Conductivity of ZnO Thin Films Prepared on Glass Substrates by Chemical Bath Deposition

Abstract

The effects of annealing on the chemical composition and other properties of ZnO thin films prepared on glass substrates by chemical bath deposition are described. The atomic ratio [Zn]:[O] of the unannealed film measured by electron probe X-ray microanalysis (EPMA) is 45:55, lower than the ideal ratio 50:50. It gradually increases toward the ideal ratio with increasing annealing temperature up to 500°C. The change in the atomic ratio [Zn]:[O] is interpreted to be due to the content of remaining Zn(OH) 2 , whose existence in films is determined by the analysis of the O1S peak in X-ray photoelectron spectroscopy (XPS) spectra, that decreases with increasing annealing temperature. The increase in electrical conductivity is observed on annealed films. This is also interpreted to be due to the decrease in the content of remaining Zn(OH) 2 . Notable changes in crystallinity and optical transmission by annealing are not observed.