Rectification of sulphur deficiency defect in CdS based films by introducing a novel modification in the SILAR cyclic process

Abstract

In the present study, a novel modification is introduced in the dipping process of the SILAR (successive ionic layer adsorption and reaction) technique which is one of the important chemical solution techniques, generally used for the deposition of cadmium sulphide films. This study clearly establishes that this improved SILAR (ISILAR) technique enables one to rectify the sulphur deficiency, generally present in CdS films and there by obtain a near stoichiometric undoped and doped CdS thin films. In the present work, Fe doped CdS thin films are also deposited on glass substrates using this ISILAR technique. In this ISILAR technique, during the automated dipping process, a fresh anionic solution bath replaces the used one when the supply of S2− ions from this anionic solution declines to an optimized threshold value. As a result of this modification, the stoichiometric deviation drastically reduces from 12.9% to 3.3% for CdS films and from 20.2% to 0.6% for CdS:Fe films. The underlying mechanism for this observed improvement in the stoichiometry is elaborated in this article. The CdS films deposited using this ISILAR technique exhibit better transmittance values compared to several reported values. The XRD studies reveal that the deposited films have good crystalline quality. The magnetic studies show that at higher Fe doping (15 at.%) level, a ferromagnetic nature is observed in the lower applied magnetic field region. The optical band gap decreases gradually with the increase in the Fe doping level and this result is found to be supported by photoluminescence results.