Hydrogen impurities in chemical bath deposited CdS

Chemical bath deposition is a well-established process for the fabrication of thin CdS films for electro-optic devices. We investigate the various imp urities in this material with emphasis on hydrogen-related compounds. Nucle ar reaction analysis provides hydrogen depth profiles of chemically deposit ed CdS with mean concentrations up to 12 atom Fb hydrogen. Using photoelect ron spectroscopy only a part of this amount can be ascribed to bonds with o ther impurities. The distribution of hydrogen in CdS thin films exhibits a clear dependence on the concentration of precursor substances in the bath a nd the deposition time. The accumulation of hydrogen in the film during pro cessing has been determined and may be explained by a diffusion process alo ng grain boundaries of the polycrystalline CdS. We demonstrate the variatio n of hydrogen and other impurity concentrations upon vacuum annealing. As a result of our investigations, we suggest a single hydrogen species is incl uded during the deposition process in order to account for the hydrogen sur plus found. A chemical reaction capable of supplying the observed individua l hydrogen species is presented. (C) 1999 The Electrochemical Society. S001 3-4651(98)09-076-4. All rights reserved.