Işık, Mehmet

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https://hdl.handle.net/20.500.14411/8160
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Mehmet, Işık
M.,Işık
Isik, Mehmet
Mehmet, Isik
I., Mehmet
I.,Mehmet
Işık,M.
Isik,M.
I.,Mehmet
M.,Isik
Işık, Mehmet
M., Isik
Isik, M.
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Profesör Doktor
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mehmet.isik@atilim.edu.tr
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Department of Electrical & Electronics Engineering
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Former Staff
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Scholarly Output

173

Articles

169

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JournalCount
Optical Materials17
Physica B: Condensed Matter16
Journal of Luminescence15
Materials Science in Semiconductor Processing14
Journal of Materials Science: Materials in Electronics12
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Scholarly Output Search Results

Now showing 1 - 10 of 20
  • Thumbnail Image
    Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Interband Critical Points in Tlgax< Layered Mixed Crystals (0 ≤ x ≤ 1)
    (Elsevier Science Sa, 2013) Isik, M.; Işık, Mehmet; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
    The layered semiconducting TlGaxIn1-xS2 mixed crystals (0 <= x <= 1) were studied by spectroscopic ellipsometry measurements in the 1.2-6.2 eV spectral range at room temperature. The spectral dependence of the components of the complex dielectric function, refractive index and extinction coefficient were revealed using an optical model. The interband transition energies in the studied samples were found from the analysis of the second-energy derivative spectra of the complex dielectric function. The variation of the obtained energies with composition were plotted to see the effect of the substitution of indium with gallium. Moreover, a simple diagram showing the revealed transitions in the available electronic band structure was given for TlGaS2 single crystals. (C) 2013 Elsevier B.V. All rights
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    Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Absorption Edge and Optical Constants of Tl2ga2< Crystals From Reflection and Transmission, and Ellipsometric Measurements
    (Elsevier, 2012) Isik, M.; Gasanly, N. M.
    The optical properties of Tl2Ga2S3Se layered crystalline semiconductors were investigated from transmission, reflection and ellipsometric measurements. The experimental results of the room temperature transmission and reflection measurements performed in the wavelength range of 400-1100 nm showed the presence of both indirect and direct transitions in the band structure of the crystals with 2.38 and 2.62 eV band gap energies. Spectroscopic ellipsometry measurements on Tl2Ga2S3Se crystals were carried out on the layer-plane (0 0 1) surfaces with light polarization E perpendicular to c* in the 1.20-4.70 eV spectral range at room temperature. The real and imaginary parts of the dielectric function as well as refractive and absorption indices were found as a result of analysis of ellipsometric data. The Wemple-DiDomenico single-effective-oscillator model was used to study the dispersion of the refractive index in the below band gap energy range. The structures of critical points have been characterized from the second derivative spectra of the dielectric function. The analysis revealed four interband transition structures with 3.14, 3.40, 3.86 and 4.50 eV critical point energies. (C) 2012 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Optical Parameters of Anisotropic Chain-Structured Tl2ingate4< Crystals by Spectroscopic Ellipsometry
    (Elsevier Gmbh, 2016) Isik, M.; Gasanly, N. M.
    Spectroscopic ellipsometry measurements were performed on Tl2InGaTe4 single crystals in the 1.2-6.2 eV range for orientations of electric field, parallel (E//c) and perpendicular (E perpendicular to c) to optic axis c. Spectral dependence of optical parameters; real and imaginary components of the dielectric function, refractive index and extinction coefficient were obtained from the analyses of experimental data using an ambient-substrate optical model. The analysis of the absorption data calculated using the extinction coefficient showed the existence of indirect transitions in the crystal with an energy band gap of similar to 0.72 eV for both orientations. Interband transition (critical point) energies were revealed using second-energy derivative spectra of the dielectric function. The results showed the presence of five each interband transition structures for E//c and E perpendicular to c orientations. (C) 2016 Elsevier GmbH. All rights reserved.
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    Article
    Citation - WoS: 24
    Citation - Scopus: 22
    Spectroscopic Ellipsometry Study of Above-Band Gap Optical Constants of Layered Structured Tlgase2, Tlgas2 and Tlins2 Single Crystals
    (Elsevier Science Bv, 2012) Isik, M.; Gasanly, N. M.; Turan, R.
    Spectroscopic ellipsometry measurements on TlGaSe2, TlGaS2 and TlInS2 layered crystals were carried out on the layer-plane (0 0 1) surfaces, which are perpendicular to the optic axis c*, in the 1.2- 6.2 eV spectral range at room temperature. The real and imaginary parts of the pseudodielectric function as well as pseudorefractive index and pseudoextinction coefficient were found as a result of analysis of ellipsometric data. The structures of critical points in the above-band gap energy range have been characterized from the second derivative spectra of the pseudodielectric function. The analysis revealed four, five and three interband transition structures with critical point energies 2.75, 3.13, 3.72 and 4.45 eV (TlGaSe2), 3.03, 3.24, 3.53, 4.20 and 4.83eV (TlGaS2), and 3.50, 3.85 and 4.50 eV (TlInS2). For TlGaSe2 crystals, the determined critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure. (c) 2012 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 3
    Citation - Scopus: 4
    Optical Properties of Cu3in5< 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.
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    Article
    Citation - WoS: 9
    Citation - Scopus: 10
    Spectroscopic Ellipsometry Investigation of Optical Properties of Β-ga2s3< Single Crystals
    (Elsevier Science Bv, 2018) Isik, M.; Gasanly, N. M.; Gasanova, L.
    Ga2S3 single crystals were studied by x-ray diffraction (XRD), energy dispersive spectroscopy and spectroscopic ellipsometry measurements. XRD pattern of the sample is well-matched with reported hexagonal structure of beta-Ga2S3 . The spectra of real and imaginary parts of complex dielectric function (epsilon = epsilon(1) + epsilon(2)) and refractive index (N = n + ik) were plotted in the 1.2-6.2 eV range according to results of ellipsometric data. The e 2 -spectrum and analyses of absorption coefficient pointed out that studied sample has band gap energy of 2.48 eV which is consistent with that of beta-Ga(2)S(3)2. Critical point energies of beta-Ga2S3 were also reported in the present study.
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    Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Exploring the Linear and Nonlinear Optical Behavior of (tlins2)0.75(tlinse2)0.25: Insights From Ellipsometry Measurements
    (Elsevier, 2023) Isik, M.; Guler, I.; Gasanly, N.
    The search for layered structured new semiconductor materials with remarkable optical properties has become a driving force, especially for materials science. Tl2In2S3Se [(TlInS2)0.75(TlInSe2)0.25], a fascinating compound, holds great promise for advanced photonic and optoelectronic applications. In the present study, the linear and nonlinear optical properties of Tl2In2S3Se layered single crystals were studied by ellipsometry measurements. The variation of refractive index, extinction coefficient, absorption coefficient and skin depth with energy were investigated. Applying the derivative analysis technique to the absorption spectrum, indirect bandgap was found as 2.19 eV. The refractive index data was analyzed considering single-effective-oscillator model. The lattice dielectric constant, plasma frequency, carrier density to the effective mass ratio and zero-frequency refractive index were found. Moreover, the change in optical conductivity with energy yielded to determine the direct bandgap as 2.40 eV. The optical parameters of nonlinear refractive index, first-and third-order nonlinear susceptibilities were also reported.
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    Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Spectroscopic Ellipsometry Studies of Optical Properties of Tlin(s0.25se0.75< Crystal
    (Springer Heidelberg, 2023) Guler, I.; Isik, M.; Gasanly, N.
    The optical properties of TlIn(S0.25Se0.75)(2) crystals were studied by ellipsometry measurements. X-ray diffraction pattern presented well-defined peaks associated with monoclinic structure. Energy dependent graphs of various linear optical parameters of the crystal were presented in the 1.25-4.50 eV range. The band gap and Urbach energies of the compound were found as 1.96 and 0.68 eV, respectively, from the analyses of the absorption coefficient. Refractive index spectrum was analyzed considering the single-effective-oscillator model to get oscillator and dispersion energies, zero and high frequency dielectric constants, plasma frequency. Moreover, the nonlinear refractive index, first-order and third-order nonlinear susceptibilities of TlIn(S0.25Se0.75)(2) crystal were revealed in the present paper.
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    Article
    Citation - WoS: 12
    Citation - Scopus: 12
    Interband Transitions in Gallium Sulfide Layered Single Crystals by Ellipsometry Measurements
    (Elsevier, 2013) Isik, M.; Gasanly, N. M.; Turan, R.
    Spectroscopic ellipsometry measurements on the GaS single crystals are presented in the energy range of 1.2 - 6.2 eV at room temperature. Optical constants; pseudorefractive index, pseudoextinction coefficient, real and imaginary parts of the pseudodielectric function were determined. Analysis of the second derivative of real and imaginary parts of the pseudodielectric constant revealed five transitions with critical point energies of 3.95, 4.22, 4.51, 4.75 and 5.50 eV. These energies were assigned to interband transitions according to theoretical study of GaS band structure available in literature. (C) 2012 Elsevier B.V. All rights reserved.
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    Article
    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.