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Öğe 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 MamedSnS2 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.Öğe Optical and structural characteristics of electrodeposited Cd 1-xZnxS nanostructured thin films(Elsevier B.V., 2021) Ertürk, Kadir; Işık, M.; Terlemezoğlu, Makbule; Gasanly, Nizami MamedThe structural and optical characteristics of Cd1-xZnxS (CdZnS) thin films grown by the electrodeposition method were investigated in the present paper. The crystalline structure of the grown CdZnS thin film was determined as cubic wurtzite due to observed diffraction peaks associated with (111) and (220) planes. Atomic compositional ratios of the constituent elements were obtained using energy dispersive spectroscopy and doping concentration of the Zn was found as 5% (x ~ 0.05). Scanning electron microscopy image of the studied thin film indicated that grown film is nanostructured. Raman spectra of CdS and CdZnS thin films were measured and it was seen that observed longitudinal optical modes for CdZnS present a blue-shift. Temperature-dependent band gap energy characteristics of the thin films were studied performing transmission experiments in the 10–300 K temperature range. The analyses of the recorded transmittance spectra showed that direct band gap energy of the films decreases from 2.56 eV (10 K) to 2.51 eV (300 K) with the increase of temperature. The band gap energy vs. temperature dependency was studied applying well-known Varshni optical model and various optical parameters of the films were reported according to the results of the applied model. © 2021 Elsevier B.V.Öğe Temperature dependence of band gaps in sputtered SnSe thin films(Elsevier Ltd, 2019) Delice, S.; Işık, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Parlak, Mehmet; Gasanly, Nizami MamedTemperature-dependent transmission experiments were performed for tin selenide (SnSe) thin films deposited by rf magnetron sputtering method in between 10 and 300 K and in the wavelength region of 400–1000 nm. Transmission spectra exhibited sharp decrease near the absorption edge around 900 nm. The transmittance spectra were analyzed using Tauc relation and first derivative spectroscopy techniques to get band gap energy of the SnSe thin films. Both of the applied methods resulted in existence of two band gaps with energies around 1.34 and 1.56 eV. The origin of these band gaps was investigated and it was assigned to the splitting of valence band into two bands due to spin-orbit interaction. Alteration of these band gap values due to varying sample temperature of the thin films were also explored in the study. It was seen that the gap energy values increased almost linearly with decreasing temperature as expected according to theoretical knowledge. © 2019 Elsevier LtdÖğe 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, MehmetStructural 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 LtdÖğe Temperature-dependent material characterization of CuZnSe2 thin films(Elsevier B.V., 2020) Güllü, H. H.; Surucu, O.; Terlemezoğlu, Makbule; Işık, M.; Ercelebi, C.; Gasanly, Nizami Mamed; Parlak, MehmetIn the present work, CuZnSe2 (CZSe) thin films were co-deposited by magnetron sputtering of ZnSe and Cu targets. The structural analyses resulted in the stoichiometric elemental composition and polycrystalline nature without secondary phase contribution in the film structure. Optical and electrical properties of CZSe thin films were investigated using temperature-dependent optical transmission and electrical conductivity measurements. The band gap energy values were obtained using transmittance spectra under the light of expression relating absorption coefficient to incident photon energy. Band gap energy values were found in decreasing behavior from 2.31 to 2.27 eV with increase in temperature from 10 to 300 K. Temperature-band gap dependency was evaluated by Varshni and O'Donnell models to detail the optical parameters of the thin films. The experimental dark and photoconductivity values were investigated by thermionic emission model over the grain boundary potential. Room temperature conductivity values were obtained in between 0.91 and 4.65 (× 10?4 ??1cm?1) under various illumination intensities. Three different linear conductivity regions were observed in the temperature dependent profile. These linear regions were analyzed to extract the activation energy values. © 2020 Elsevier B.V.Öğe Temperature-dependent optical characteristics of sputtered NiO thin films(Springer Science and Business Media Deutschland GmbH, 2022) Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Işık, Mehmet; Gasanly, Nizami Mamed; Parlak, MehmetIn this work, nickel oxide thin films were deposited by radio frequency magnetron sputtering technique. X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray analysis methods were applied to reveal the structural and morphological properties of sputtered thin films. The XRD pattern of films confirmed the presence of the cubic phase of nickel oxide with the preferential orientation of (200) direction. The surface morphology of thin films was observed as almost uniform and smooth. Optical aspects of sputtered film were studied by employing the room temperature Raman and temperature-dependent transmittance spectroscopy techniques in the range of 10–300 K. Tauc relation and derivative spectroscopy techniques were applied to obtain the band gap energy of the films. In addition, the relation between the band gap energy and the temperature was investigated in detail considering the Varshni optical model. The absolute zero band gap energy, rate of change of band gap energy, and Debye temperature were obtained as 3.57 eV, ? 2.77 × 10–4 eV/K and 393 K, respectively. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.Öğe Temperature-tuned band gap properties of MoS2 thin films(Elsevier B.V., 2020) Sürücü, Özge; Işık, Mehmet; Gasanly, Nizami Mamed; Terlemezoğlu, Makbule; Parlak, MehmetMoS2 is one of the fascinating members of transition metal dichalcogenides and has attracted great attention due to its various optoelectronic device applications and its characteristic as two-dimensional material. The present paper reports the structural and temperature tuned optical properties of MoS2 thin films grown by RF magnetron sputtering technique. It was observed that the atomic composition ratio of Mo:S was nearly equal to 1:2 and the deposited thin films have hexagonal crystalline structure exhibiting Raman peaks around 376 and 410 cm?1. The band gap energies were determined as 1.66 and 1.71 eV at 300 and 10 K, respectively and temperature dependency of band gap energy was analyzed by means of Varshni and O'Donnell-Chen models. © 2020 Elsevier B.V.Öğe Vibrational modes in ( TlGaS2)x?(TlGaSe2)1?x mixed crystals by Raman measurements: compositional dependence of the mode frequencies and line?shapes(Springer, 2020) Işık, M.; Terlemezoğlu, Makbule; Gasanly, Nizami Mamed; Babayeva, R.F.TlGaS2 and TlGaSe2 ternary semiconducting compounds have been of scientific interest due to their large ultrafast optical nonlinearity characteristics. These remarkable properties make them promising semiconducting materials in photonic applications. A series of (TlGaS2)x?(TlGaSe2)1?x layered mixed crystals grown by Bridgman method were investigated from the standpoint of their Raman spectroscopy characteristics. Experimental Raman scattering study of crystals were reported in the frequency range of 80–400 cm?1 for compositions of x = 0, 0.25, 0.50, 0.75 and 1.0. The effects of crystal disorder on the line-width broadening of Raman-active modes were studied in detail. The asymmetry in the Raman line-shape was analyzed for two highest-frequency intralayer mode presenting two-mode behavior. It was shown that mixed crystal disorder effect is the major source for change of Raman line-shape with composition. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
