Effects of bath temperature on the properties of chemical bath-deposited FeS x O y films

Iron-sulphide-oxide (FeS x O y ) thin films were prepared on fluorine-tin-oxide (FTO)-coated glass substrate for 3-h-deposition times via chemical bath deposition (CBD) from an aqueous solution, containing 100 mM sodium thiosulphate (Na 2 S 2 O 3 ), 30 mM iron (II) sulphate heptahydrate (FeSO 4 ·7H 2 O) and 50 mM L(+)-tartaric acid (C 4 H 6 O 6 ) as the complexing agent. The effects of bath temperature (45–90°C) on FeS x O y film properties including optical, structural, impurities, composition and surface morphology were studied. Characterization equipment, such as scanning electron microscopy equipped with energy dispersive X-ray spectroscopy: thickness estimated from the cross-section image, surface morphology and composition; X-ray diffraction: crystallinity/amorphous; Raman spectra: impurities; UV–vis spectroscopy: transmittance and bandgap estimation; and Hot Probe method: photoresponse, has been used in analysing the properties of the deposited films. The optimum bath temperature of 75°C has resulted in better film quality in terms of compactness, uniformity and crystallinity (larger crystallite size). All the deposited films exhibited n-type photoresponse with a large bandgap of 3.36–3.57 eV, which could be associated with crystallinity (crystallite size), phase purity and high oxygen content (>50%).