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Article Citation - WoS: 2Citation - Scopus: 2Trap Distribution in Agin5s8< Single Crystals: Thermoluminescence Study(Pergamon-elsevier Science Ltd, 2018) Delice, S.; Işık, Mehmet; Isik, M.; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringDistribution of shallow trap levels in AgIn5S8 crystals has been investigated by thermoluminescence (TL) measurements performed below room temperature (10-300 K). One broad TL peak centered at 33 K was observed as constant heating rate of 0.2 K/s was employed for measurement. The peak shape analysis showed that the TL curve could consist of several individual overlapping TL peaks or existence of quasi-continuous distributed traps. Therefore, TL experiments were repeated for different stopping temperatures (T-stop) between 10 and 34 K with constant heating rate of 0.2 K/s to separate the overlapping TL peaks. The E-t vs T-stop indicated that crystal has quasi-continuously distributed traps having activation energies increasing from 13 to 41 meV. Heating rate effect on trapped charge carriers was also investigated by carrying out the TL. experiments with various heating rates between 0.2 and 0.6 K/s for better comprehension of characteristics of existed trap levels. Analyses indicated that the trap levels exhibited the properties of anomalous heating rate behavior which means the TL intensity and area under the TL peak increase with increasing heating rate.Article Citation - WoS: 20Citation - Scopus: 24Temperature Dependence of Band Gaps in Sputtered Snse Thin Films(Pergamon-elsevier Science Ltd, 2019) Delice, S.; Isik, M.; Gullu, H. H.; Terlemezoglu, M.; Surucu, O. Bayrakli; Parlak, M.; Gasanly, N. M.Temperature-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.Article Citation - WoS: 4Citation - Scopus: 4Transmission, Reflection and Thermoluminescence Studies on Gas0.75se0.25< Layered Single Crystals(Pergamon-elsevier Science Ltd, 2015) Delice, S.; Isik, M.; Gasanly, N. M.Optical and thermoluminescence properties on GaS0.75Se0.25 crystals were investigated in the present work. Transmission and reflection measurements were performed at room temperature in the wavelength range of 400-1000 nm. Analysis revealed the presence of indirect and direct transitions with band gap energies of 2.39 and 2.53 eV, respectively. TL spectra obtained at low temperatures (10-300 K) exhibited one peak having maximum temperature of 168 K. Observed peak was analyzed using curve fitting, initial rise and peak shape methods to calculate the activation energy of the associated trap center. All applied methods were consistent with the value of 495 meV. Attempt-to-escape-frequency and capture cross section of the trap center were determined using the results of curve fitting. Heating rate dependence studies of the glow curve in the range of 0.4-0.8 K/s resulted with decrease of TL intensity and shift of the peak maximum temperature to higher values. (C) 2015 Elsevier Ltd. All rights reserved.
