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Citation - WoS: 42
Citation - Scopus: 41
Synthesis and Characterization of Mg₂b_2<
(Pergamon-elsevier Science Ltd, 2005) Qasrawi, AF; Kayed, TS; Mergen, A; Gürü, M
Magnesium borate of the form Mg2B2O5 has been prepared and its structural and thermal properties were studied using X-ray diffraction and differential thermal analysis. An investigation of the electrical and optical properties of Mg2B2O5 system has been carried out. The electrical resistivity of the sample was measured in the temperature range of 170-400 K. The data analysis revealed an extrinsic nature of the conductivity with two impurity levels located at 0.13 and 0.71 eV in the temperature ranges of 170-230 K and 240-400 K, respectively. The optical transmission and reflection was recorded at 300 K in the incident photon energy range of 3.0-6.0 eV. The absorption coefficient data analysis revealed an indirect optical energy band gap of 4.73 eV. In addition, two impurity levels located at 3.43, and 4.49 eV were observed in the absorption spectra. (c) 2005 Elsevier Ltd. All rights reserved.
Citation - WoS: 16
Citation - Scopus: 17
Investigation of Localized Levels in Gas_0.5se_{0.5< Layered Crystals by Means of Electrical, Space-Charge Limited Current and Photoconductivity Measurements}
(Wiley-v C H verlag Gmbh, 2002) Qasrawi, AF; Gasanly, NM
To identify the localized levels in GaS0.5Se0.5 single crystals, the dark electrical conductivity, current-voltage characteristics and photoconductivity measurements were carried out in the temperature range of 250-400 K. Temperature dependence of dark electrical conductivity and the space-charge limited current studies indicate the presence of a single discrete trapping level located at 0.31 eV below the conduction band with a density of about 1.3 x 10(15) cm(-3). The conductivity data above 320 K reveal an additional donor level with activation energy of 0.40 eV indicating the extrinsic nature of conduction. The spectral distribution of photocurrent in the photon energy range of 0.65-5.9 eV reveals an indirect band gap of 2.26 eV. The photocurrent-illumination intensity dependence follows the law I-ph proportional to F-gamma, with gamma being 1.0, 0.65, and 0.5 at low, moderate and high illumination intensities, respectively. The corresponding behavior indicates the domination of monomolecular recombination, near equal densities of trapped and recombination centers and bimolecular recombination. It is observed that the photocurrent increases in the temperature range from 250 K up to T-m = 360 K and decreases for T > T-m. The temperature dependence of the photocurrent reveals two additional impurity levels with activation energies of 0.14 and 0.10 eV below and above Tm, respectively.
Citation - WoS: 13
Citation - Scopus: 13
Light Illumination Effect on the Electrical and Photovoltaic Properties of In₆s_{7< Crystals}
(Iop Publishing Ltd, 2006) Qasrawi, AF; Gasanly, NM
The electrical and photoelectrical properties of In6S7 crystals have been investigated in the temperature regions of 170-300 K and 150-300 K, respectively. The dark electrical analysis revealed the intrinsic type of conduction. The energy band gap obtained from the temperature-dependent dark current is found to be 0.75 eV. It is observed that the photocurrent increases in the temperature range of 150 K up to T-m = 230 K and decreases at T > T-m. Two photoconductivity activation energies of 0.21 and 0.10 eV were determined for the temperature ranges below and above Tm, respectively. The photocurrent (I-ph)-illumination intensity (F) dependence follows the law I-ph alpha F-gamma. The value of. decreases when the temperature is raised to T-m, then it starts increasing. The change in the value. with temperature is attributed to the exchange in role between the recombination and trapping centres in the crystal. The crystals are found to exhibit photovoltaic properties. The photovoltage is recorded as a function of illumination intensity at room temperature. The maximum open-circuit voltage and short-circuit photocurrent density, which are related to an illumination intensity equivalent to one sun, are 0.12 V and 0.38 mA cm(-2), respectively.
Citation - WoS: 18
Citation - Scopus: 18
Growth, Electrical and Structural Characterization of Β-Gase Thin Films
(Springer, 2003) Parlak, M; Qasrawi, AF; Erçelebi, Ç
GaSe thin films were deposited onto the glass substrates kept at 200degrees and 300degreesC by the thermal evaporation of GaSe crystals under the pressure of 10(-5) Torr. X-ray analysis of the films revealed that films grown at 200. C are amorphous in nature while the films grown at 300degreesC are polycrystalline beta-GaSe. The temperature dependent electrical conductivity measurements in the region of 320-100 K for the films grown at 300degreesC showed that the transport mechanisms are the thermionic emission of charged carriers and the variable range hopping above and below 180 K, respectively. Space charge limited current (SCLC) studies have also been performed on these films through the current-voltage measurements at different temperatures and a dominant hole trap at 0.233 eV from the top of the valance band with a trap density of similar to1.6 x 10(11) cm(-3) is identified. (C) 2003 Kluwer Academic Publishers.
Citation - WoS: 26
Citation - Scopus: 26
Etectron-Phonon Short-Range Interactions Mobility and P- To N-Type Conversion in Tlgas₂ Crystal
(Wiley-v C H verlag Gmbh, 2006) Qasrawi, AF; Gasanly, NM
The conductivity type conversion from p- to n-type at a critical temperature of 315 K in TlGaS2 crystals is observed through the Hall effect measurements in the temperature range of 200-350 K. The analysis of the temperature-dependent electrical resistivity, Hall coefficient and carrier concentration data reveals the extrinsic type of conduction with donor impurity levels that behave as acceptor levels when are empty. The data analysis allowed the calculation of hole and electron effective masses of 0.36m(0) and 0.23m(0), respectively. In addition, the temperature-dependent Hall mobility is found to decrease with temperature following a logarithmic slope of similar to 1.6. The Hall mobility in the n-region is limited by the electron-phonon short-range interactions scattering with an electron-phonon coupling constant of 0.21. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Citation - WoS: 26
Citation - Scopus: 26
Photoelectronic, optical and electrical properties of TlInS₂ single crystals
(Wiley-v C H verlag Gmbh, 2003) Qasrawi, AF; Gasanly, NM
To specify the donor energy levels in TlInS2 single crystals, the dark electrical resistivity, photoconductivity and Hall measurements were carried out in the temperature range of 100-400 K, 110-350 K and 170-400 K, respectively. The Hall measurements revealed that the crystals exhibit an anomalous behavior of Hall voltage by changing sign (from p-type to n-type conductivity) at 315 K. By means of the temperature dependence of dark electrical resistivity, Hall coefficient and photocurrent measurements the donor energy levels located at 360, 280, 152 and 112 meV were detected. The photocurrent-illumination intensity dependence follows the law I-Ph proportional to F-gamma with gamma being 1.0 (linear), 0.5 (sublinear), 1.0 (linear) and 1.3 (supralinear) at low, moderate, high and very high illumination intensities indicating the monomolecular in the bulk, bimolecular and strong recombination at the surface, respectively. The photocurrent is observed to increase with increasing temperature up to a maximum temperature (T-m) 245 K. T is observed to shift to higher temperature as F increases, and disappears in the region where I-Ph-F dependence is supralinear. The phenomenon is attributed to the exchange in the behavior of the sensitizing and recombination centers. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.
Citation - WoS: 28
Citation - Scopus: 27
Photoelectronic and Electrical Properties of Cuin₅s_{8< Single Crystals}
(Wiley-v C H verlag Gmbh, 2003) Qasrawi, AF; Gasanly, NM
To identify the impurity levels in CuIn5S8 single crystals, the dark electrical conductivity and photoconductivity measurements were carried out in the temperature range of 50-460 K. The data reflect the intrinsic and extrinsic nature of the crystals above and below 300 K, respectively. Energy band gaps of 1.35 and 1.31 eV at 0 K and 300 K, were defined from the dark conductivity measurements and the photocurrent spectra, respectively. The dark and photoconductivity data in the extrinsic temperature region reflect the existence of two independent donor energy levels located at 130 and 16 meV. The photocurrent-illumination intensity dependence (F) follows the law I(ph)alphaF(gamma), with gamma being 1.0, 0.5 and 1.0 at low, moderate and high intensities indicating the domination of monomolecular, bimolecular and strong recombination at the surface, respectively. In the intrinsic region and in the temperature region where the shallow donor energy level 16 meV is dominant, the free electron life time, tau(n), is found to be constant with increasing F. In the temperature region 140 K < T < 210 K, the free electron life time increases with increasing illumination intensity showing the supralinear character. Below 140 K, tau(n) decrease with decreasing illumination intensity. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Citation - WoS: 26
Citation - Scopus: 26
Fabrication and Some Physical Properties of Agin₅s_{8< Thin Films}
(Elsevier Science Sa, 2004) Qasrawi, AF; Kayed, TS; Ercan, I
AgIn5S8 thin films are deposited on glass substrates, kept at 300 K, by thermal evaporation of AgIn5S8 single crystals under the pressure of 10-5 Torr. The X-ray fluorescence analysis revealed that the films have a weight percentage of similar to11.5% Ag, 61.17% In, and 27.33% S which corresponds to 1:5:8 stoichiometric composition. X-ray analysis of the films reveals the polycrystalline nature of the films. The lattice parameter (a) of the films was calculated to be 10.784(5) Angstrom. The dark n-type electrical conductivity of the films was measured in the temperature range of 30-350 K. The conductivity data analysis shows that the thermionic emission of the charge carriers having activation energies of 147 and 224 meV in the temperature ranges of 130-230 and 240-350 K, respectively, are the dominant transport mechanism in the films. The variable range hopping transport mechanism is dominant below 130 K. The room temperature photocurrent-photon energy dependency predicts a band gap of 1.91 eV of the films. The illumination intensity-photocurrent dependency measured in the intensity range of 13-235 W cm(-2) reveals monomolecular recombination (linear) in the films and bimolecular recombination (sublinear) at the film surface corresponding to low and high applied illumination intensities, respectively. The time-dependant photocurrent measured at fixed illumination intensity reveals a response time of 0.85, 2.66 and 10.0 s in the time periods of 0-0.5, 0.5-1.0, and 1.0-10.0 s, respectively. (C) 2004 Elsevier B.V. All rights reserved.
Citation - WoS: 27
Citation - Scopus: 30
Crystal Data, Electrical Resistivity, and Hall Mobility of N-Type Agin₅s_{8< Single Crystals}
(Wiley-v C H verlag Gmbh, 2001) Qasrawi, AF; Gasanly, NM
The X-ray diffraction has revealed that AgIn5S8 is a single phase crystal of cubic spinel structure. The value of the unit cell parameter for this crystal is 1.08286 nm. The electrical resistivity and Hall effect of n-type AgIn5S8 crystals are measured in the temperature range of 50-400 K. A carrier effective mass of 0.20 m(0), an acceptor to donor concentration ratio of 0.8 and an acoustic phonons deformation potential of 20 eV are identified from the Hall effect measurement. The Hall mobility data art: analyzed assuming the carrier scattering by acoustic and polar optical phonons, and ionized impurities.
Citation - WoS: 45
Citation - Scopus: 48
Refractive Index, Band Gap and Oscillator Parameters of Amorphous Gase Thin Films
(Wiley-v C H verlag Gmbh, 2005) Qasrawi, AF; Department of Electrical & Electronics Engineering
GaSe thin films are obtained by evaporating GaSe crystals onto ultrasonically cleaned glass substrates kept at room temperature under a pressure of similar to 10(-5) Torr. The X-ray analysis revealed that these films are of amorphous nature. The reflectance and transmittance of the films are measured in the incident photon energy range of 1.1-3.0 eV. The absorption coefficient spectral analysis revealed the existence of long and wide band tails of the localized states in the low absorption region. The band tails width is calculated to be 0.42 eV. The analysis of the absorption coefficient in the high absorption region revealed an indirect forbidden band gap of 1.93 eV. The transmittance analysis in the incidence photon wavelength range of 500-1100 nm allowed the determination of refractive index as function of wave length. The refractive index-wavelength variation leads to the determination of dispersion and oscillator energies as 31.23 and 3.90 eV, respectively. The static refractive index and static dielectric constant were also calculated as a result of the later data and found to be 9.0 and 3.0, respectively.

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