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    Effect of $SnCl_2$ heat treatment on SnS thin films deposited by RF sputtering
    (2023) Çiriş, Ali
    In this study, the effect of $SnCl_2$ treatment on SnS thin films was investigated. SnS thin films were grown by RF sputtering and $SnCl_2$ treatment was applied by wet chemical processing. While the samples grouped as $SnCl_2$ heat treated and annealed were subjected to annealing in air atm, the as-deposited sample was not applied any annealing process. The as-deposited sample grew in the orthorhombic SnS phase. Annealing of the SnS sample in air environment led to the formation of orthorhombic SnS as well as non-dominant $SnCl_2$ and $SnCl_2$ phases. It was found that applying $SnCl_2$ heat treatment to SnS deteriorated the crystallization and especially the $SnO_2$ oxide phase became more dominant. Raman spectra confirmed the presence of SnS and SnS2 phases in the samples, but no evidence of $SnO_2$ phase was found. SEM images showed bladelike, dense grain formation in the as-deposited and annealed samples. However, $SnCl_2$ heat treatment completely changed the surface morphology of the sample, causing it to transform into a structure consisting of several domains split by deep fractures. EDS revealed a distinct Sn-rich composition of the as-deposited and annealed samples (Sn/S~1.2). On the other hand, $SnCl_2$ heat treatment caused a massive loss of sulphur in the atomic distribution of the SnS and it was seen that the Sn/S ratio increased to around 7.5. The band gaps of the as-deposited and annelaed samples were calculated as 1.43 eV and 1.45, respectively. However, $SnCl_2$ heat treatment led to an increase to 1.56 eV of the band gap. Analysis results show that $SnCl_2$ treatment by the wet processing causes a significant change on the characteristics of SnS thin film. In this context, it can be said that $SnCl_2$ heat treatment can be further improved with optimization processes.
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    Fabrication of SnS thin film by rapid thermal processing: effect of annealing temperature in sulfurization process
    (2022) Çiriş, Ali; Olğar, Mehmet Ali
    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 ?.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.