Influence of precursor concentration and annealing treatment on the structural and optical properties of sol gel ZnO thin films.

In this work, ZnO thin films were fabricated using the sol-gel spin coating process and their structural and optical characteristics were investigated for various precursor concentrations and annealing temperatures. Nanocrystalline ZnO thin films were successfully deposited on glass and silicon substrates using Zinc acetate dihydrate as the precursor material. X-ray diffraction (XRD) results show that the obtained ZnO films have a (002) preferential orientation, which depends strongly on precursor concentration and substrate nature. The Scherer formula reveals that the crystallites have a nanometric character and their average size varies between 10 and 40 nm. Scanning electron microscopy (SEM) exam showed granular surface with a relatively dense structure. Using spectrophotometry, the measured transmittance of the ZnO thin film ranged from 75 to 95% in the visible light region. The variation of the direct band gap energy with the concentration of precursor and the annealing temperature is not very significant. The prepared ZnO thin films show an average band gap energy value evaluated at 3.31 ev

In Situ Low-Temperature Chemical Bath Deposition of CdS Thin Films without Thickness Limitation: Structural and Optical Properties

In this work, thin CdS films have been deposited using the chemical bath deposition technique (CBD). Different synthesis parameters, such as number of runs, deposition time, and postannealing temperature, are studied and optimized in order to avoid the supersaturation phenomenon and to achieve a low-temperature growth. CdS thin films, of cubic structure, oriented along the (111) direction with homogenous and smooth surface, have been deposited by using the CBD growth process without any annealing treatment. Based on a set of experimental observations, we show that the solution saturation phenomenon can be avoided if the deposition is performed in several runs at a short deposition time. Throughout the CBD technique, it is then possible not only to overcome any film thickness limitation but also to grow the CdS films in a single technological step at a low temperature and without any postdeposition annealing treatment. CdS films with excellent structural quality and a controllable thickness are obtained when the deposition bath temperature is fixed at 65°C. In addition, deposited films exhibit an optical transmittance ranging from 70 to 95% depending on the synthesis parameters, with band gap energy around 2.42 eV. The process developed in this work might be useful for depositing CdS films on flexible substrates