Işık, Mehmet

Işık, Mehmet

Profile URL

https://hdl.handle.net/20.500.14411/8160

Name Variants

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.

Job Title

Profesör Doktor

Email Address

mehmet.isik@atilim.edu.tr

Main Affiliation

Department of Electrical & Electronics Engineering

Status

Former Staff

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Sustainable Development Goals

2

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0

Research Products

11

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14

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1

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10

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7

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11

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4

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12

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3

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This researcher does not have a Scopus ID.

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Scholarly Output

173

Articles

169

Views / Downloads

447/809

Supervised MSc Theses

3

Supervised PhD Theses

0

WoS Citation Count

1818

Scopus Citation Count

1870

WoS h-index

20

Scopus h-index

20

Patents

0

Projects

0

WoS Citations per Publication

10.51

Scopus Citations per Publication

10.81

Open Access Source

11

Supervised Theses

3

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Journal	Count
Optical Materials	17
Physica B: Condensed Matter	16
Journal of Luminescence	15
Materials Science in Semiconductor Processing	14
Journal of Materials Science: Materials in Electronics	12

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Scholarly Output Search Results

Now showing 1 - 10 of 24

Citation - WoS: 23
Citation - Scopus: 25
Investigation of Optical Properties of Bi₁₂geo_{20< Sillenite Crystals by Spectroscopic Ellipsometry and Raman Spectroscopy}
(Elsevier Sci Ltd, 2020) Isik, M.; Delice, S.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.
Bi12GeO20 (BGO) compound is one of the fascinating members of sillenites group due to its outstanding photorefractive and photocatalytic characteristics. The present paper aims at investigating optical properties of BGO crystals by means of spectroscopic ellipsometry and Raman spectroscopy measurements. Bi12GeO20 single crystals grown by Czochralski method were structurally characterized by X-ray diffraction (XRD) experiments and the analyses showed that studied crystals have cubic crystalline structure. Raman spectrum exhibited 15 peaks associated with A, E and F modes. Spectroscopic ellipsometry measurement data achieved in the energy region between 1.2 and 6.2 eV were used in the air/sample optical model to get knowledge about complex pseudodielectric constant, pseudorefractive index, pseudoextinction and absorption coefficients of the crystals. Spectral change of real and imaginary part of complex pseudodielectric constant were discussed in detail. Band gap energy of Bi12GeO20 single crystals was calculated to be 3.18 eV using absorption coefficient dependency on photon energy. Critical point energies at which photons are strongly absorbed were determined by utilizing the second energy derivative spectra of components of complex pseudodielectric function. Fitting of both spectra resulted in the presence of four interband transitions with energies of 3.49, 4.11, 4.67 and 5.51 eV.
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.
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: 9
Citation - Scopus: 11
Spectroscopic Ellipsometry Investigation of Optical Properties of Β-ga₂s_{3< 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.
Citation - WoS: 2
Citation - Scopus: 2
Optical Characterization of Nabi(moo₄)_{2< Crystal by Spectroscopic Ellipsometry}
(Springer Heidelberg, 2024) Guler, I.; Isik, M.; Gasanly, N. M.
The compound NaBi(MoO4)(2) has garnered significant interest in optoelectronic fields. This study employs spectroscopic ellipsometry to thoroughly examine the linear and nonlinear optical characteristics of NaBi(MoO4)(2) crystals, offering detailed insights into their optical behavior. Our investigation presents a precise method for discerning the crystal's spectral features, revealing the spectral variations of key optical parameters such as refractive index, extinction coefficient, dielectric function, and absorption coefficient within the 1.2-5.0 eV range. Through analysis, we determined optical attributes including bandgap energy, critical point energy, and single oscillator parameters. Additionally, we explored the nonlinear optical properties of NaBi(MoO4)(2), unveiling potential applications such as optoelectronic devices, frequency conversion, and optical sensors. This study enhances comprehension of optical properties of NaBi(MoO4)(2), underscoring its significance in future optical and electronic advancements.
Citation - WoS: 1
Citation - Scopus: 2
Spectroscopic Ellipsometry Studies of Optical Properties of Tlin(s_0.25se_{0.75< 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.
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.
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.
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: 10
Citation - Scopus: 10
Ellipsometry Study of Optical Parameters of Agin₅s_{8< Crystals}
(Elsevier, 2015) Isik, Mehmet; Gasanly, Nizami
Agln(5)S(8) crystals grown by Bridgman method were characterized for optical properties by ellipsometry measurements. Spectral dependence of optical parameters; real and imaginary parts of the pseudodielectric function, pseudorefractive index, pseudoextinction coefficient, reflectivity and absorption coefficient were obtained from ellipsometiy experiments carried out in the 1.2-6.2 eV range. Direct band gap energy of 1.84 eV was found from the analysis of absorption coefficient vs. photon energy. The oscillator energy, dispersion energy and zero-frequency refractive index, high-frequency dielectric constant values were found from the analysis of the experimental data using Wemple-DiDomenico and Spitzer-Fan models. Crystal structure and atomic composition ratio of the constituent elements in the AgIn5S8 crystal were revealed from structural characterization techniques of X-ray diffraction and energy dispersive spectroscopy. (C) 2015 Elsevier B.V. All rights reserved

Işık, Mehmet

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Sustainable Development Goals

2

ZERO HUNGER

0

Research Products

11

SUSTAINABLE CITIES AND COMMUNITIES

0

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14

LIFE BELOW WATER

1

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6

CLEAN WATER AND SANITATION

0

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1

NO POVERTY

0

Research Products

5

GENDER EQUALITY

0

Research Products

9

INDUSTRY, INNOVATION AND INFRASTRUCTURE

0

Research Products

16

PEACE, JUSTICE AND STRONG INSTITUTIONS

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17

PARTNERSHIPS FOR THE GOALS

0

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15

LIFE ON LAND

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10

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AFFORDABLE AND CLEAN ENERGY

11

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8

DECENT WORK AND ECONOMIC GROWTH

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QUALITY EDUCATION

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12

RESPONSIBLE CONSUMPTION AND PRODUCTION

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GOOD HEALTH AND WELL-BEING

1

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CLIMATE ACTION