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Citation - WoS: 7
Citation - Scopus: 7
Trapping Centers and Their Distribution in Tl₂ga_{2< Layered Single Crystals}
(Pergamon-elsevier Science Ltd, 2009) Isik, M.; Gasanly, N. M.
Thermally stimulated current (TSC) measurements with current flowing perpendicular to the layers were carried out on Tl2Ga2Se3S layered single crystals in the temperature range of 10-260K. The experimental data were analyzed by using different methods, such as curve fitting, initial rise and isothermal decay methods. The analysis revealed that there were three trapping centers with activation energies of 12, 76 and 177 meV. It was concluded that retrapping in these centers was negligible, which was confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. The capture cross section and the concentration of the traps have been also determined. An exponential distribution of electron traps was revealed from the analysis of the TSC data obtained at different light illumination temperatures. This experimental technique provided values of 10 and 88 meV/decade for the traps distribution related to two different trapping centers. (C) 2009 Elsevier Ltd. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 4
Optical Properties of Cu₃in_{5< Single Crystals by Spectroscopic Ellipsometry}
(Elsevier Gmbh, 2018) Isik, M.; Nasser, H.; Ahmedova, F.; Guseinov, A.; Gasanly, N. M.
Cu3In5S9 single crystals were investigated by structural methods of x-ray diffraction and energy dispersive spectroscopy and optical techniques of ellipsometry and reflection carried out at room temperature. The spectral dependencies of optical constants; dielectric function, refractive index and extinction coefficient, were plotted in the range of 1.2-6.2 eV from ellipsometric data. The spectra of optical constants obtained from ellipsometry analyses and reflectance spectra presented a sharp change around 1.55 and 1.50 eV, respectively, which are associated with band gap energy of the crystal. The critical point (interband transition) energies were also found from the analyses of second-energy derivative of real and imaginary components of dielectric function. The analyses indicated the presence of four critical points at 2.73, 135, 4.04 and 4.98 eV.
Citation - WoS: 10
Citation - Scopus: 10
Determination of Mechanical Properties of Bi₁₂tio_{20< Crystals by Nanoindentation}
(Elsevier Sci Ltd, 2022) Isik, M.; Gasanly, N. M.; Rustamov, F. A.
Bi12TiO20 (BTO) single crystal was grown by Czochralski method and investigated mechanically by nano-indentation measurements. X-ray diffraction pattern of the crystal presented one intensive peak around 37.95 degrees associated with (330) plane of cubic crystalline structure. Nanoindentation experiments were performed at various loads between 5 and 100 mN. Hardness and Young's modulus of the crystal were determined by Oliver-Pharr method. The hardness-load dependency exhibited behavior of indentation size effect. True hardness value of BTO crystal was revealed as 4.4 GPa. Young's modulus decreased with increase of load and load-independent Young's modulus was found around 93 GPa at high loads. The load-dependent elastic and plastic deformation components were calculated and it was observed that the dominant component in BTO single crystal is plastic deformation at the applied loads. The present paper reports for the first time the mechanical characteristics of the BTO single crystal by carrying out nanoindentation experiments.
Citation - WoS: 2
Citation - Scopus: 2
Trap Distribution in Agin₅s_{8< 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 Engineering
Distribution 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.
Citation - WoS: 19
Citation - Scopus: 20
Optical characteristics of Bi₁₂SiO₂₀ single crystals by spectroscopic ellipsometry
(Elsevier Sci Ltd, 2020) Isik, M.; Delice, S.; Nasser, H.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.
Structural and optical characteristics of Bi12SiO20 single crystal grown by the Czochralski method were investigated by virtue of X-ray diffraction (XRD) and spectroscopic ellipsometry measurements. XRD analysis indicated that the studied crystal possesses cubic structure with lattice parameters of a = 1.0107 nm. Spectral dependencies of several optical parameters like complex dielectric constant, refractive index, extinction and absorption coefficients were determined using ellipsometry experiments performed in the energy region of 1.2-6.2 eV. The energy band gap of Bi12SiO20 crystals was found to be 3.25 eV by utilizing absorption coefficient analysis. Moreover, critical point energies were calculated as 3.54, 4.02, 4.82 and 5.58 eV from analyses of the second energy derivative spectra of the complex dielectric constant.
Citation - WoS: 1
Citation - Scopus: 1
Temperature -Dependent Optical and Electrical Characterization of Cu-Ga Thin Films and Their Diode Characteristics on N-Si
(Elsevier Gmbh, 2020) Gullu, H. H.; Isik, M.; Gasanly, N. M.; Parlak, M.
In this paper, optical and electrical properties of thermally deposited Cu-Ga-S thin films were investigated using temperature-dependent optical transmission and electrical conductivity measurements. The analysis of the transmission spectra resulted in formation of three direct optical transitions due to the possible valence band splitting in the structure. The band gap values were calculated by means of absorption coefficient and incident photon energy was found in decreasing behavior as the temperature rises. The measured current-voltage values were used to extract the conductivity values which stand in the range of 1.73-2.62 (x104 O-1 cm-1) depending on the ambient temperature. These dark conductivity values were modeled by thermionic emission mechanism. The conductivity activation energies in the structures were calculated as 6.4, 14.5 and 40.7 meV according to the effects of grain boundary potentials. In addition, the films deposited on n-Si wafer showed a diode characteristic under the applied bias voltage between indium (In) front and silver (Ag) back contacts. From current-voltage measurements across the Si-based diode, about four orders of magnitude rectification was observed and the results were analyzed to determine the main diode parameters at dark and room temperature conditions.
Citation - WoS: 5
Citation - Scopus: 5
Structural and Optical Properties of Thermally Evaporated (gase)0.75-(gas)0.25 Thin Films
(Elsevier Gmbh, 2021) Isik, M.; Işık, Mehmet; Emir, C.; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
GaSe and GaS binary semiconducting compounds are layered structured and have been an attractive research interest in two-dimensional material research area. The present paper aims at growing (GaSe)0.75 - (GaS)0.25 (or simply GaSe0.75S0.25) thin film and investigating its structural and optical properties. Thin films were prepared by thermal evaporation technique using evaporation source of its single crystal grown by Bridgman method. The structural properties were revealed using x-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. XRD pattern and EDS analyses indicated that thin films annealed at 300 ?C were successfully deposited and its structural characteristics are well-consistent with its single crystal form. Surface morphology was studied by means of SEM and AFM measurements. Optical properties were investigated by transmission and Raman spectroscopy techniques. Raman spectrum exhibited three peaks around 172, 242 and 342 cm-1. Analyses of transmission spectrum revealed the direct band gap energy as 2.34 eV. The mixed compounds of GaSe0.75S0.25 were prepared for the first time in a thin film form and the results of the present paper would provide valuable information to research area in which layered compounds have been studied in detail.
Citation - WoS: 14
Citation - Scopus: 14
Low Temperature Thermoluminescence Behaviour of Y₂o_{3< Nanoparticles}
(Elsevier, 2019) Delice, S.; Isik, M.; Gasanly, N. M.
Y2O3 nanoparticles were investigated using low temperature thermoluminescence (TL) experiments. TL glow curve recorded at constant heating rate of 0.4 K/s exhibits seven peaks around 19, 62, 91, 115, 162, 196 and 215 K. Activation energies and characteristics of traps responsible for observed curves were revealed under the light of results of initial rise analyses and T-max-T-stop experimental methods. Analyses of TL curves obtained at different stopping temperatures resulted in presence of one quasi-continuously distributed trap with activation energies increasing from 18 to 24 meV and six single trapping centers at 49, 117, 315, 409, 651 and 740 meV. Activation energies of all revealed centers were reported in the present paper. Structural characterization of Y2O3 nanoparticles was accomplished using X-ray diffraction and scanning electron microscopy measurements. (C) 2019 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Characterization of T1ins1.8se0.2 as Advanced Functional Crystals
(Elsevier Sci Ltd, 2018) Qasrawi, A. F.; Atatreh, Areen A. M.; Gasanly, N. M.
In this work, selenium doped TlInS1.8Se0.2 crystals are used to fabricate multifunctional devices that can handle more than one duty at a time. After revealing the morphological, compositional, structural and optical properties of the doped crystal, it is sandwiched between Ag and carbon metals. The crystals are characterized by means of ultraviolet-visible light spectrophotometry, impedance spectroscopy and illumination dependent current-voltage characteristics techniques. While the optical spectroscopy allowed determining the energy band gap of the crystals as well as the optical conductivity in the terahertz frequency domain, the impedance spectroscopy allowed identifying the conductance and reflectance spectra in the gigahertz frequency domain. The two techniques reveal promising characteristics presented by optical switching at 2.20 eV and band pass filtering properties in mega/gigahertz frequency domains. On the other hand, the analysis of the current (I)- voltage (V) characteristics which are recorded in the dark and under photoexcitation of unfiltered tungsten light in the light power range of 25-130 mW, revealed light intensity dependent rectifying properties. Particularly, the modeling of the experimental I-V curves in accordance with the Richardson Schottky and Chueng's theoretical approaches have shown that the Schottky diode ideality factor, series resistance and barrier height decreases with increasing light power. Such behavior indicates wide tunability of the device when used as photosensors. With the features presented by small size, photosensitivity, gigahertz/terahertz spectral responses, the device can be promising element for use in visible light and microwave communications.
Citation - WoS: 10
Citation - Scopus: 10
Temperature Effects on Optical Characteristics of Cdse Thin Films
(Elsevier Sci Ltd, 2021) Gullu, H. H.; Isik, M.; Surucu, O.; Gasanly, N. M.; Parlak, M.
CdSe is one of the significant members of II-VI type semiconducting family and it has a wide range of technological applications in which optoelectronic devices take a special position. The present paper reports the structural and optical characteristics of thermally evaporated CdSe thin films. XRD pattern exhibited preferential orientation along (111) plane while atomic composition analyses resulted in the ratio of Cd/Se as closer to 1.0. Temperature-dependent band gap characteristics of CdSe thin films were investigated for the first time by carrying out transmission experiments in the 10-300 K range. The analyses showed that direct band gap energy of the compound decreases from 1.750 (at 10 K) to 1.705 eV (at 300 K). Varshni model was successfully applied to the temperature-band gap energy dependency and various optical constants were determined. Raman spectrum of CdSe thin films was also presented to understand the vibrational characteristics of the compound. The present paper would provide worthwhile data to researchers especially studying on optoelectronic device applications of CdSe thin films.

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