Influence of deposition pressure of elemental Sn on structural, optical, electrical and schottky diode properties of SnS thin films grown by two-stage method

Abstract

In the present study, SnS thin films were grown by two-stage method including sputtering deposition of elemental Sn films at various deposition pressures (6, 9, 12 ,15 and 18 mTorr) followed by sulfurization process carried out by Rapid Thermal Processing method at 350 degrees C for 1 min. The fabricated SnS thin films were characterized by several techniques. The energy dispersive X-ray spectroscopy measurements showed that deviation from stoichiometry in chemical composition of SnS samples deposited at above 9 mTorr was observed. X-ray diffraction and Raman spectroscopy measurements confirmed formation of orthorhombic SnS phase and SnS2 secondary phase. Furthermore, both characterization method also revealed that the preferential orientation of orthorhombic SnS phase altered from (111) to (040) by increasing the deposition pressure at above 9 mTorr. Scanning electron microscope images displayed formation of polycrystalline surface morphology. While lower deposition pressure (6 mTorr) gave rise to form small grains, the high deposition pressure (above 12 mTorr) caused some agglomerations. Optical bandgap of the films varied between 1.02 eV and 1.08 eV by varying the deposition pressure. SnS samples prepared at 9 and 12 mTorr deposition pressures presented lower resistivity and higher carrier concentration values. Due to more promising results of SnS samples fabricated utilizing 9 and 12 mTorr deposition pressures regarding structural and electrical properties, Schottky diode properties of both samples were investigated. The current-voltage characteristic of Mo/SnS/Al diode structure showed that SnS samples prepared at 12 mTorr has more ideal diode characteristic, comparatively.