Structure and properties of SnS films prepared by electro-deposition in presence of EDTA

SnS thin films were deposited onto indium tin oxide (ITO) glass substrates by constant potential cathodic electro-deposition from aqueous solution containing stannous sulfate, ethylenediamine tetraacetate acid and sodium thiosulfate. The co-deposited potential was explored by cyclic voltammetry and the deposition potential (E) was roughly determined to be more negative than -0.70 V (vs. saturated calomel electrode, SCE). The analysis of the composition of the as-deposited films by X-ray fluorescence spectrometer indicated that stoichiometric SnS films could be obtained under the condition of E = -0.95 to -1.00 V. The films deposited at E = -1.00 V were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and their transmission and reflectance spectra were measured. The as-deposited films were polycrystalline SnS compound with orthorhombic crystalline structure and the ratio of Sn and S was nearly 1. The films were uniform and compact with small grains. The direct band gap of the films was estimated to be about 1.10-1.43 eV with an absorption coefficient near the fundamental absorption edge larger than 4 x 10(4) cm(-1). (C) 2008 Elsevier B.V. All rights reserved.