Effect of one-step electrodeposition time on the physical properties of tin sulfide thin films

Abstract

A one-step potentiostatic electrochemical deposition technique was used to deposit tin sulfide (SnS) thin films onto an ITO-coated glass substrate at room temperature. The present work aims to investigate the effect of the electrodeposition time on various physical properties of SnS semiconductors. The emphasis will be placed on determining the time necessary to cover the entire surface of the substrate with a first layer of SnS and on studying the effect of the conductivity of this first layer on the further growth of the SnS layers. Different electrodeposition times were considered, and the obtained samples were examined using appropriate techniques. X-ray diffraction reveals the orthorhombic polycrystalline nature for all samples and shows that the intensity of pure SnS peaks increases with increasing deposition time. Beyond 40 min of electrodeposition, XRD analysis shows the appearance of SnS secondary phases such as SnS₂ and Sn₂S₃. Raman characterization unveils a behavior change detected from 40 min of electrodeposition and confirms the presence of peaks characteristic of the SnS, Sn₂S₃, and SnS₂ phases. SEM images reveal that the first SnS layer completely covers the substrate surface between 30- and 40-min electrodeposition. EDX Analysis has shown that to achieve SnS layer stoichiometry, it is necessary to deposit SnS on substrates with high conductivity. Optical characterization confirms that transmittance decreases with increasing deposition time reflecting an increase in SnS layer thickness. The band gaps were identified as direct ones with energies around 1.3 eV for all samples and correlated both to the thickness of the layers and/or to the crystallite size.