CdHgSe thin films: preparation, characterization and optoelectronic studies

We present a modified chemical bath deposition method used to grow Cd1-xHgxSe (0 < x < 1) pseudo-binary thin films with the objective to study growth kinetics, structural, optical and electrical changes. The method is based on the reaction of CdSO4, Hg(NO3)(2) and Na2SeSO3 in an aqueous ammonical medium at a temperature of 5 degreesC. The reactant concentration, pH, deposition temperature and rate of agitation were found to influence significantly the quality and thickness of the films. The as-deposited thin films were characterized by x-ray diffraction (XRD), atomic absorption spectrophotometry, scanning electron microscopy, optical absorption and thermoelectrical techniques. The XRD study confirms the polycrystalline nature in a single cubic phase over the whole range of composition studied. The grain size is found to be similar for all compositions. An analysis of absorption spectra gave a direct type optical bandgap, the magnitude of which decreases monotonically as mercury content (x) in the film is increased while dark dc electrical conductivity at room temperature was found to increase nonlinearly from 10(-6) to 10(2) Omega(-1) cm(-1). All the films showed n-type conductivity. The main features observed are the formation of continuous solid solutions in a single cubic phase, the absence of other crystallographic phases, the lack of solubility gap, and stability.