Effects of Solution pH on Chemical Bath Deposited Iron-Sulfide-Oxide with Tartaric Acid Presence

A chemical bath deposition (CBD) contained sodium thiosulfate (Na2S2O3), iron (II) sulfate heptahydrate (FeSO4.7H2O), and L(+)-tartaric acid (C4H6O6) as the complexing agent has been used to deposit the iron-sulfide-oxide (FeSxOy) films. The effects of different solution pH (5.0-9.0) on film properties were investigated. The thicknesses of the film analysed from the cross-sectional images of Scanning Electron Microscopy (SEM) showed the thickness of the film is increasing with increasing pH. The X-Ray Diffraction (XRD) pattern and the hot probe method revealed that all the deposited films are crystalline, and possess n-type semiconductor behaviour due to high oxygen content (around 72-82%). Larger crystallite sizes with extra peaks of goethite and hematite were present for the films with pH > 7.0, while, better film uniformity and grains distribution, as well as clear absorption edge in transmittance measurement, were obtained for the film with pH 5.0.