CdS thin films on LiNbO3 (1 0 4) and silicon (1 1 1) substrates prepared through an atom substitution method

CdS thin films on LiNbO3 (1 0 4) and silicon (1 1 1) substrates were prepared through an atom substitution technique using cadmium nitrate as a reactant in an H2S atmosphere at 230 °C. X−ray diffraction, scanning electron microscopy and transmission microscopy results indicate that the CdS film grows on LiNbO3 oriented along the [0 0 1] axis in form of crystallized nanoplates, while that deposited on silicon forms randomly oriented nanoparticles. Investigation of the precursor thin film suggests that CdS forms from the O in the CdO precursor thin film being substituted by S from H2S in the surrounding environment, which is designated as an atom substitution process. This novel method involving an atom substitution reaction between the CdO precursor thin film and its environment can provide a new low cost approach to the preparation of chalcogenide or other compound thin films. A schematic illustration and corresponding mechanism describing the details of this method are proposed.