Preparation of ZnO membrane by chemical bath deposition method via regulated acidity

Abstract

In this study, the chemical bath deposition (CBD) method was used to deposit a ZnO membrane on an indium tin oxide glass substrate. The deposition reaction working temperature was 90°C and the temperature retaining deposition time was 60 min; NH₄OH was used to control the pH value in the range 10~11, and after deposition, the specimen was thermally annealed in air. Annealing temperatures in the range of 100~500°C were adopted to investigate the thin-film growth behavior and the effect of processing temperature on the ZnO membrane performance during the annealing process. The process parameters related to the preparation of the ZnO membrane by CBD were the pH value, retaining temperature deposition time, working temperature for the deposition reaction, annealing thermal processing, and so on. Scanning electron microscopy (SEM) was used to observe and analyze the surface morphology and microstructure of the membrane cross section, and UV-Vis spectrometry was used to measure the optical transmission of the ZnO membrane in air at different annealing temperatures. We investigated the effects of different pH values on the growth of the ZnO membrane by CBD. The experimental results show that at a pH of 10.7, we can obtain a transparent and electrically conductive ZnO thin film with a thickness of 240 nm, which has very good optical transmission and high electrical mobility at an annealing temperature of 200°C.

Keywords: Chemical bath deposition, ZnO membrane, pH value