Fabrication of SnS thin film by rapid thermal processing: effect of annealing temperature in sulfurization process

Abstract

In this study, the effect of sulfurization temperature on properties of SnS thin films was investigated. The SnS thin films were fabricated by two-stage method includes deposition of SnS films by magnetron sputtering using a single SnS target, followed by annealing/sulfurization treatment in Rapid Thermal Processing (RTP) system at 225, 300 and 375 °C temperatures. Several characterization techniques such as XRD, Raman spectroscopy, EDX, optical transmission and Van der Pauw were used for analyses of the films. The EDX analyses showed that all the samples had almost stoichiometric (S/Sn~1) chemical composition. However, the amount of sulfur in the samples increased slightly as the sulfurization temperature increased. XRD pattern of the films exhibited constitution of orthorhombic SnS structure regardless of annealing temperature. The SnS2 secondary phase was observed in addition to orthorhombic SnS phase in the sample annealed at highest reaction temperature (375°C). Raman spectroscopy measurements of the films verified constitution of orthorhombic SnS structure. The band gap of the films exhibited distinction from 1.42 to 1.81 eV regarding to annealing temperature. The electrical characterization of the most promising SnS thin film sulfurized at 300°C had resistivity and charge carrier concentration values 1.07x104 Ω.cm and 1.70x1014 cm-3, respectively. Based on the all characterizations, it can be deduced that SnS thin film sulfurized at 300°C exhibited more outstanding structural and optical properties for potential solar cell applications.