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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: 30
Citation - Scopus: 30
Optoelectronic and Electrical Properties of Tlgas₂ Single Crystal
(Wiley-v C H verlag Gmbh, 2005) Qasrawi, AF; Gasanly, NM
The optoelectronic and electrical properties of TIGaS2 single crystals have been investigated by means of room temperature transmittance and reflectance spectral analysis, Hall coefficient, dark electrical resistivity and photocurrent measurements in the temperature range of 200-350 K. The optical data have revealed an indirect and direct allowed transition band gaps of 2.45 and 2.51 eV, an oscillator and dispersion energy of 5.04 and 26.45 eV, respectively, a static dielectric constant of 6.25 and static refractive index of 2.50. The dark Hall coefficient measurements have shown that the crystals exhibit a conductivity type conversion from p-type to n-type at a critical temperature of 315 K. Deep donor and acceptor energy levels of 0.37/0.36 eV and 0.66 eV has been calculated from the temperature dependence of Hall coefficient and resistivity, and photocurrent measurements, respectively. The photocurrent decreases with decreasing temperature. The analysis of the photocurrent data have revealed that, the recombination mechanism is linear and supralinear above and below 290 K, respectively. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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: 15
Citation - Scopus: 15
Refractive Index, Static Dielectric Constant, Energy Band Gap and Oscillator Parameters of Ga₂ses Single Crystals
(Wiley-v C H verlag Gmbh, 2007) Qasrawi, A. F.; Gasanly, N. M.
The optical properties of Bridgman method grown Ga2SeS crystals have been investigated by means of room-temperature transmittance and reflectance spectral analysis. The optical data have revealed direct and indirect allowed transition band gaps of 2.49 and 2.10 eV, respectively. The room-temperature refractive index, which was calculated from the reflectance and transmittance data, allowed the identification of the dispersion and oscillator energies, static dielectric constant and static refractive index as 20.93 eV and 4.01 eV, 6.21 and 2.49, respectively.
Citation - WoS: 143
Citation - Scopus: 149
A Novel Neutral State Green Polymeric Electrochromic With Superior N- and P-Doping Processes: Closer To Red-Blue (rgb) Display Realization
(Wiley-v C H verlag Gmbh, 2008) Cihaner, Atilla; Algi, Fatih
Two donor-acceptor systems, 4,7-di-2-thienyl-2,1,3-benzoselenadiazole (TSeT) and 4,7-di-2,3-dehydrothieno[3,4-b][1,4]dioxin-5yl-2,1,3-benzoselenadiazole (ESeE) are synthesized and electropolymerized to give polymers PTSeT and PESeE, respectively. One of the polymers, PTSeT, is blue-green in the neutral state and soluble, exhibiting a deep-red emission color. The other, PESeE, is the first 2,1,3-benzoselenadiazole-based neutral state green polymer with a narrow bandgap (1.04eV). Furthermore, PESeE has superior and durable n- and p-doping processes. Beyond the stability and the robustness, both of the polymer films exhibit multi-electrochromic behavior.
Citation - WoS: 4
Citation - Scopus: 4
Determination of Carrier Effective Mass, Impurity Energy Levels, and Compensation Ratio in Ga₄se_{3< Layered Crystals by Hall Effect Measurements}
(Wiley-v C H verlag Gmbh, 2008) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Gasanly, N. M.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
In this work, the dark electrical resistivity, charge carriers density and Hall mobility of Ga4Se3S single crystals have been measured and analyzed in the temperature region of 200-350 K. The data analyses have shown that this crystal exhibits an extrinsic n-type of conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of energy level as 0.31 eV. The temperature dependence of carrier density was analyzed by using the single donor-single acceptor model. The latter analysis allowed the determination of electron effective mass as 0.38m(0), hole effective mass as 0.42m(0), donor impurity energy level as 0.45 eV, acceptor-donor concentration ratio (N-a/N-d) as 0.97 and a donor-acceptor concentration difference as N-d - N-a = 1.5 x 10(11) cm(-3). The Hall mobility of Ga4Se3S is found to increase with decreasing temperature following a power law of slope of similar to(-6.3). The abnormal behavior of mobility was attributed to the domination of phonon scattering and/or crystals anisotropy. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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