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Article Citation - WoS: 5Citation - Scopus: 5Growth and Temperature Tuned Band Gap Characteristics of Nabi(moo4)2< Single Crystal(Iop Publishing Ltd, 2023) Isik, M.; Guler, I; Gasanly, N. M.Structural and optical properties of double sodium-bismuth molybdate NaBi(MoO4)(2) semiconductor compound was investigated by x-ray diffraction, Raman and transmission experiments. From the x-ray diffraction experiments, the crystal that has tetragonal structure was obtained. Vibrational modes of the crystal were found from the Raman experiments. Transmission experiments were performed in the temperature range of 10-300 K. Derivative spectroscopy analysis and absorption spectrum analysis were performed to get information about the change in band gap energy of the crystal with temperature. It was observed that the band gap energies of the crystal at different temperatures obtained from these techniques are well consisted with each other. By the help of absorption spectrum which was obtained from transmission measurements performed at varying temperatures, absolute zero value of the band gap and average phonon energy as 3.03 +/- 0.02 eV and Eph = 24 +/- 0.2 meV, respectively. Moreover, based on absorption spectrum analysis the Urbach energy of the crystal was obtained as 0.10 eV.Article Citation - WoS: 16Citation - Scopus: 15Effect of Temperature on Band Gap of Pbwo4 Single Crystals Grown by Czochralski Method(Iop Publishing Ltd, 2022) Isik, M.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.The structural and optical properties of PbWO4 single crystals grown by Czochralski method and investigated by x-ray diffraction (XRD) and transmission experiments. XRD pattern presented well-defined and intensive peaks related with tetragonal scheelite structure. Transmission experiments were accomplished for the first time at various temperatures between 10 and 300 K on PbWO4 single crystals to reveal variation of band gap with temperature. Derivative spectroscopy method presented the experimentally observed band gap energy as increasing from 3.20 to 3.35 eV when the temperature was decreased to 10 K from room temperature. The revealed energy was associated with transition taking place between delocalized and trap levels. Temperature-band gap energy plot was analyzed by Varshni and Bose-Einstein models. The fitting processes under the light of these models revealed optical characteristics of absolute zero experimentally observed band gap, variation rate of gap energy with temperature and Debye temperature of PbWO4 single crystal.Article Citation - WoS: 5Citation - Scopus: 6Influence of Temperature on Optical Properties of Electron-Beam Znse Thin Film(Iop Publishing Ltd, 2020) Gullu, H. H.; Isik, M.; Gasanly, N. M.; Parlak, M.Structural and optical properties of ZnSe thin films grown by electron-beam evaporation technique were reported in the present paper. X-ray diffraction pattern exhibited a single peak around 27 degrees which is well-suited with cubic phase of the films. Energy dispersive X-ray spectroscopy analyses resulted in atomic composition ratio of Zn/Se nearly 1.0 which corresponds to the chemical formula of ZnSe. Transmission experiments were performed at various temperatures in between 10 and 300 K. The analyses of the transmission data showed that direct band gap energy of the ZnSe thin films increases from 2.72 to 2.83 eV as temperature was reduced to 10 K from room temperature. The Varshni and O'Donnell-Chen models giving the temperature-band gap energy relation were used to get various optical parameters of the evaporated thin films. Analyses resulted in absolute zero temperature band gap energy as 2.83 eV, temperature coefficient as -5.8 x 10(-4) eV K-1 and average phonon energy as 16 meV. Urbach tail state energies were also calculated using absorption coefficient in the low photon energy region as increasing from 173 meV (300 K) to 181 meV (10 K) with decreasing ambient temperature.
