Polymorphic tin sulfide thin films of zinc blende and orthorhombic structures by chemical deposition

Polycrystalline thin films (100-450 nm in thickness) of SnS formed from chemical baths of Sn(II) in acetic acid/HCl solution, triethanolamine, NH3 (aq), and thioacetamide are polymorphic consisting of zinc blende (ZB) and orthorhombic (OR) structures. The ZB structure for the SnS film, reported in this work for the first time, has a lattice constant a = 0.579 nm and a direct (forbidden) bandgap of 1.7 eV, which is distinct from that of SnS(ZB), about 1 eV. The electrical conductivity of SnS(ZB) is 6 x 10(-6) (ohm cm)(-1) p-type, with activation energies for the conductivity of 0.5 eV at room temperature and 1.6 meV near 10 K. When a SnS(ZB) film is heated in air at 500 degrees C for 30 min, part of it transforms to SnO2 and to SnS (OR); after 2 h 30 min at 550 degrees C in air the film converts to transparent SnO2. Such a film has a bandgap of 3.7 eV and electrical conductivity, similar to 1 (ohm cm)(-1). Photovoltaic effect in different structures involving these films is presented. (c) 2008 The Electrochemical Society.