Thickness dependent properties of chemically deposited As2S3 thin films from thioacetamide bath

A low temperature chemical deposition method has been developed to deposit semiconducting nanocrystalline arsenic trisulphide thin films on ordinary glass substrates with different thicknesses. The deposition bath consists of aqueous acidic arsenic trioxide, disodium salt of ethylenediaminetetra-acetic acid (Na2EDTA) and thioacetamide. It is found that the deposition parameters significantly influence the quality and the thickness of As2S3 films. The films were uniform and adherent to glass substrates. The deposited films were characterized by X-ray diffraction, scanning electron microscope (SEM), atomic force microscope (AFM), optical absorption, electrical resistivity and thermo-emf measurements. The effect of film thickness on crystallite grain size and optical bandgap of As2S3 film was studied. It is found that as the thickness increases, optical bandgap and electrical resistivity decreases. Such type of dependence is attributed to the quantum size effect in semiconductors. Films showed n-type conductivity with thermo-emf measurement.