Physics Group
Permanent URI for this collection
Browse
Browsing Physics Group by Author "Delice, Serdar"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Article Growth and temperature-tuned band gap characteristics of LiGd(MoO4)2 single crystals for optoelectronic applications(Ceramics International, 2023-08-01) Delice, Serdar; Işık, Mehmet; Gasanly, Nizami Mamed; Darvishov, Namiq H.; Bagiev, Vidadi E.LiGd(MoO4)2 has been investigated due to its optoelectronic applications, especially for development of light-emitting diodes. In the present paper, LiGd(MoO4)2 single crystals grown by Czochralski method was studied in terms of structural and temperature dependent optical properties. X-ray diffraction analysis showed that the crystal crystallizes in a single phase tetragonal structure. Raman spectrum exhibited six distinguishable peaks around 207, 319, 397, 706, 756 and 890 cm−1. These peaks correspond to vibrational modes of free rotation, symmetrical stretching, symmetric bending, antisymmetric stretching and antisymmetric bending of (MoO4)2− tetrahedron. Infrared transmittance spectrum had six minima around 2114, 2350, 2451, 2854, 2929, 2960, 3545 and 3578 cm−1 which are due to multiphonon absorptions. Spectral change of transmittance curves at various temperature between 10 and 300 K was utilized to elucidate temperature effect on absorption characteristics. Optical band gap of the material was found using Tauc and spectral derivative methods. The band gap value was obtained as 3.09 eV at room temperature and this value increased to 3.22 eV with decreasing temperature down to 10 K. The detailed analysis on the temperature dependency of the band gap was applied by Varshni model and the band gap at 0 K and change of rate of the band gap were estimated as 3.23 eV and −1.45 × 10−3 eV/K, respectively. Room temperature photoluminescence spectrum of the crystal presented a peak around 709 nm which corresponds to red light emission. LiGd(MoO4)2 is a potential candidate for optoelectronic devices emitting red light.Article Temperature dependence of band gap of CeO2 nanoparticle photocatalysts(Physica E: Low-dimensional Systems and Nanostructures, 2023-06) Işık, Mehmet; Delice, Serdar; Gasanly, Nizami MamedCerium dioxide (CeO2) have been one of the attractive photocatalysts material in recent years. Band gap and its change with temperature takes remarkable attention in the photocatalytic applications. The present work reported structural and temperature-dependent band gap characteristics of the CeO2 nanoparticles on glass substrate. X-ray diffraction (XRD) pattern exhibited nine peaks related to face-centered cubic structure. Crystallite size and micro-strain of the nanoparticles were determined from the analyses of XRD peaks. Scanning electron microscope (SEM) image indicated that CeO2 is in the form of nanoparticle with almost cube shaped of diameters in between 20-30 nm. Transmission measurements were performed in the 350-700 nm range at various temperatures between 10-300 K. The analyses of the transmission spectra showed that direct band gap energy decreases from 3.35 to 3.29 eV when sample temperature was raised from 10 K to room temperature. The temperature dependence of band gap energy was analyzed by Varshni expression. The analysis presented absolute zero and rate of change of band gap with temperature as 3.35 eV and −4.7×10-4 eV/K, respectively.Article Temperature-Dependent Optical Properties of TiO2 Nanoparticles: A Study of Band Gap Evolution(Optical and Quantum Electronics, 2023-10) Işık, Mehmet; Delice, Serdar; Gasanly, Nizami MamedIn this study, we present the first comprehensive investigation of the temperature-dependent band gap energy of anatase TiO2 nanoparticles, utilizing transmission measurements in the range of 10-300 K. X-ray diffraction pattern exhibited nine peaks related to tetragonal crystal structure. Scanning electron microscope image showed that the nanoparticles with the dimensions of 25-50 nm were found as micrometer sized agglomerated. When the spectrum obtained as a result of the transmission measurements was analyzed, it was seen that the band gap energy decreased from 3.29(5) to 3.26(6) eV as the temperature was increased from 10 K to 300 K. Temperature-band gap dependence was analyzed using Varshni and O'Donnell-Chen optical models and optical parameters of the TiO2 nanoparticles like absolute zero band gap energy, rate of change of band gap with temperature and average phonon energy were reported.Article Temperature-dependent tuning of band gap of Fe3O4 nanoparticles for optoelectronic applications(Chemical Physics Letters, 2024-02-19) Delice, Serdar; Işık, Mehmet; Gasanly, Nizami MamedWe have investigated structural, morphological and temperature dependent absorption characteristics of Fe3O4 nanoparticles. X-ray diffraction pattern exhibited six diffraction peaks belonging to the cubic phase structure with lattice parameter of a = 8.1602 Å. Spectral variation of absorption coefficient were utilized to achieve Tauc and spectral derivative analyses providing the band gap of the Fe3O4 at varying temperature. The band gap of Fe3O4 nanoparticles was found around 2.08 eV at 300 K and around 2.14 eV at 10 K. The band gap variation with applied temperatures between 10 and 300 K were also investigated using Varshni relation.