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    Investigation of band gap energy versus temperature for SnS2 thin films grown by RF-magnetron sputtering
    (Elsevier B.V., 2020) Işık, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Surucu, O.B.; Parlak, Mehmet; Gasanly, Nizami Mamed
    SnS2 thin films grown by magnetron sputtering technique were characterized by structurally and optically in the present work. Crystalline parameters, atomic compositions, and surface characteristics of SnS2 thin films were presented according to results of applied structural techniques. Optical studies of SnS2 thin films were accomplished by Raman spectroscopy and transmission methods. Raman spectrum exhibited two modes around 198 and 320 cm?1. Transmittance data obtained for various temperatures between 10 and 300 K were analyzed to reveal various optical characteristics like band gap energy, variation rate of gap energy with temperature, average phonon energy, gap energy at absolute zero. Band gap energy of SnS2 thin films were reported as 2.18 and 2.22 eV at 300 and 10 K, respectively. The temperature-band gap energy dependency was analyzed taking into account the Varshni and O'Donnell-Chen models. © 2020 Elsevier B.V.
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    Material and Si-based diode analyses of sputtered ZnTe thin films
    (Springer, 2020) Güllü, H. H.; Surucu, O.B.; Işık, M.; Terlemezoğlu, Makbule; Parlak, Mehmet
    Structural, optical, and electrical properties ZnTe thin films grown by magnetron sputtering technique were studied by X-ray diffraction, atomic force microscopy, Raman spectroscopy, and electrical conductivity measurements. Structural analyses showed that ZnTe thin films grown on soda–lime glass substrates have a cubic crystalline structure. This crystalline nature of the films was also discussed in terms of Raman active modes. From atomic force microscopy images, the smooth and dense surface profile was observed. The conductivity of the film at room temperature was measured as 2.45 × 10?4 (? cm)?1 and the temperature dependency of conductivity showed Arrhenius behavior. The dark conductivity profile was modeled by thermionic emission mechanism and activation energies were extracted. In addition, the conductivity values indicated an increasing behavior with illumination intensity applied between 20 and 115 mW/cm2. The heterojunction diode was generated by sputtering ZnTe film on n-Si wafer substrate and the rectification behavior was evaluated to determine the main diode parameters. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
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    Temperature dependent band gap in SnS2xSe(2-2x) (x = 0.5) thin films
    (Elsevier Ltd, 2020) Delice, S.; Işık, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Surucu, O.B.; Gasanly, Nizami Mamed; Parlak, Mehmet
    Structural and optical properties of SnS2xSe(2-2x) thin films grown by magnetron sputtering method were investigated for composition of x = 0.5 (SnSSe) in the present study. X-ray diffraction, energy dispersive X-ray spectroscopy, atomic force microscopy and scanning electron microscopy methods were used for structural characterization while temperature-dependent transmission measurements carried out at various temperatures in between 10 and 300 K were accomplished for optical investigations. X-ray diffraction pattern of studied composition presented peaks at positions which are between those of SnSe2 and SnS2. Transmittance spectra recorded at all applied temperatures were analyzed using well-known Tauc relation. Analyses revealed the direct band gap energy value of SnSSe thin films as 1.75 eV at room temperature. Change of band gap energy as a response to varying temperature were discussed in the study by utilizing Varshni relation. It was shown that variation of gap energy values was well-matched with the Varshni's empirical formula. Energy band gap at absolute zero and rate of change of band gap with temperature were found to be 1.783 eV and ?2.1 × 10?4 eV K?1, respectively. © 2020 Elsevier Ltd