Electrodeposited and characterization of Ag-Sn-S semiconductor thin films

Thin film of silver tin sulfides (Ag-Sn-S) has been deposited on indium tin oxide coated glass (ITO) substrates using potentiostatic cathodic electrodeposition technique. New procedure for the growth of Ag-Sn-S film is presented. An electrolyte solution containing Silver Nitrate (AgNO3), Tin(II) Chloride (SnCl2) and Sodium Thiosulfate (Na2S2O3)in acidic solution (pH ~2) and at temperature of the bath 55 °C were used for the growth of Ag-Sn-S thin film. Prior to the deposition, a cyclic voltammetry technique was performed in binary (Ag-S, Sn-S) and ternary (Ag-Sn-S) systems. This study was carried out to examine the behavior of electroactive species at the electrode surface. Based on these results, the cathodic applied potential was fixed at −1000 mV versus Ag/AgCl to obtain a uniform and good adhesion of ternary thin film. After that, structural, morphological and optical performances of films have been investigated. The X-ray diffraction patterns of the samples demonstrate the presence of the orthorhombic phase of Ag8SnS6 at applied potential of −1000 mV versus Ag/AgCl. Based on the scanning electron microscopy (SEM), it was found that the surface morphology and grain size were strongly influenced by the presence of Sn and/or Ag in the electrolyte bath. The band gaps of binaries and ternary compound are evaluated from optical absorption measurements. Band gap of Ag8SnS6 determined from transmittance spectra is in the range 1.56 eV. Flat-band potential and free carrier concentration have been determined from Mott-Schottky plot and are estimated to be around 0.18 V and 2.21×1014 cm−3 respectively. The photoelectrochemical test of Ag8SnS6 was studied and the experimental observations are discussed in detail.