WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 32Citation - Scopus: 33Variation of Structural and Optical Properties of Tio2 Films Prepared by Dc Magnetron Sputtering Method With Annealing Temperature(Elsevier Ltd., 2020) Gürakar, Sibel; Ot, Hakan; Horzum, Şeyda; Serin, TülayTiO2 thin films are deposited by direct current magnetron sputtering method on the silicon and quartz substrates. The effect of annealing temperature on the film properties are analysed by using X-ray diffraction (XRD), Raman scattering, atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical spectroscopy measurements. Raman and XRD results reveal that the crystal structure of the TiO2 film is strongly affected by the annealing temperature. The crystal structure of the coated film is changed from amorphous to anatase structure after annealing at 500 degrees C. Anatase and rutile phases of TiO2 start to coexist after annealing at 800 degrees C. Rutile phases of TiO2 become dominant for film annealed at 900 degrees C. SEM and AFM images uncover that the morphology, grain size and surface roughness of TiO2 films vary with the annealing temperature. The optical band gap decreases from 3.35 to 2.90 eV as the phase transforms from amorphous to rutile.Article Citation - WoS: 50Citation - Scopus: 52Monitoring the Characteristic Properties of Ga-Doped Zno by Raman Spectroscopy and Atomic Scale Calculations(Elsevier, 2019) Horzum, Şeyda; İyikanat, Fadıl; Senger, Ramazan Tuğrul; Çelebi, Cem; Sbeta, Mohamed; Yıldız, Abdullah; Serin, TülayWe experimentally and theoretically study how the structural and vibrational properties of zinc oxide (ZnO) are modified upon Gallium (Ga) doping. The characteristics of Ga-doped ZnO thin films which are synthesized by sol-gel spin coating method on glass substrates are monitored by using X-ray diffraction (XRD) and Raman scattering measurements. For atomic-level understanding of the experimental findings state-of-the-art density functional theory (DFT) based calculations are also performed. DFT calculations reveal that both the substitution and adsorption of Ga atoms in ZnO are energetically possible and substitutional doping in ZnO is the most favourable scenario. XRD measurements show that all the films are in wurtzite structure and the crystallite size of the films decreases with increasing Ga doping. In addition, Raman analysis show that strong vibrational modes at about 100 and 441 cm(-1) are associated with E-2(low) and E-2(high) phonon branches of ZnO, respectively. While the frequency of the E-2(low) mode downshifts with increasing Ga concentration, the E-2(high) phonon mode is not affected by the Ga doping. Furthermore, E-Ga phonon branch, stemming from the substituted Ga atoms, emerges at low frequencies. It is also seen that the Raman intensity of the E-G(a) peak linearly increases with increasing Ga concentration. Experimental results on the vibrational properties are in good agreement with the ab initio phonon calculations. (C) 2018 Elsevier B.V. All rights reserved.