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Electronic Structure and Redox Behavior of Tin Sulfide Films Potentiostatically Formed on Tin

The tin sulfide film, formed by potentiostatic anodic polarization of tin in aqueous electrolyte containing sulfide ions, was investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X–ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). According to XPS and Mott- Schottky (MS) tests, the surface film exhibits semiconducting properties and bilayer structure with the inner of Sn(II) sulfide layer of p–type conductivity and the outer layer of Sn(IV) sulfide layer of n–type conductivity. The film's electronic structure was discussed on the basis of band structure models, potential distribution at the interface and the availability of free charge carriers on the electrode|solution interface. The electronic structure of the passive film on tin influences its susceptibility to the oxidative as well as to the reductive solid–state decomposition. The semiconducting parameters of the sulfide film: the flatband potential, EFB, the donor concentration, ND and the optical bandgap, Eg were determined.

tin sulfide ; electrochemical impedance spectroscopy ; X-ray photoelectron spectroscopy ; semiconducting properties ; Mott-Schottky analysis ; anodic and cathodic solid-state decomposition

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