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Article Citation - WoS: 28Citation - Scopus: 27Photoelectronic and Electrical Properties of Cuin5s8< Single Crystals(Wiley-v C H verlag Gmbh, 2003) Qasrawi, AF; Gasanly, NMTo 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.Article Citation - WoS: 4Citation - Scopus: 4Electrical, Optical and Photoconductive Properties of Poly(dibenzo-18(Wiley-v C H verlag Gmbh, 2004) Qasrawi, AF; Cihaner, A; Önal, AMTo investigate the energy levels, absorption bands, band gap, dominant transport mechanisms, recombination mechanisms and the free carrier life time behavior of poly-dibenzo-18-crown-6, poly-DB18C6, films, the dark electrical conductivity in the temperature range of 200-550 K, the absorbance and photocurrent spectra, the photocurrent -illumination intensity and time dependence at 300 K were studied. The dark electrical conductivity measurements revealed the existence of three energy levels located at 0.93, 0.32 and 0.76 eV below the tails of the conduction band. The main transport mechanism in the dark was found to be due to the thermal excitation of charge carriers and the variable range hopping above and below 260 K, respectively. The photocurrent and absorbance spectra reflect a band gap of 3.9 eV. The photocurrent -illumination intensity dependence reflects the sublinear, linear and supralinear characters indicating the decrease, remaining constant and increase in the free electron life time that in turn show the bimolecular, strong and very strong recombination characters at the surface under the application of low, moderate and high illumination intensity, respectively. A response time of 25.6 s was calculated from the decay Of I-ph-time dependence. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Article Citation - WoS: 11Cd-Doping Effects on the Properties of Polycrystalline Α-in2se3< Thin Films(Wiley-v C H verlag Gmbh, 2002) Qasrawi, AFThe X-ray diffraction has revealed that the polycrystalline hexagonal structured alpha-In2Se3 thin films grown at substrate temperature of 200degreesC with the unit cell parameters a=4.03degreesA and c=19.23degreesA becomes polycrystalline hexagonal structured InSe with a unit cell parameters of a=4.00degreesA and c=16.63degreesA by Cd-doping. The analysis of the conductivity temperature dependence in the range 300-40 K revealed that the thermionic emission of charged carriers and the variable range hopping are the predominant conduction mechanism above and below 100 K, respectively. Hall measurements revealed that the mobility is limited by the scattering of charged carriers through the grain boundaries above 200 K and 120 K for the undoped and Cd-doped samples, respectively. The photocurrent (I-ph) increases with increasing illumination intensity (T) and decreasing temperature up to a maximum temperature of similar to100 K, below which I-ph is temperature invariant. It is found to have the monomolecular and bimolccular recombination characters at low and high illumination intensities, respectively. The Cd-doping increases the density of trapping states that changes the position of the dark Fermi level leading to the deviation from linearity in the dependence of I-ph on F at low illumination intensities.Article Citation - WoS: 21Citation - Scopus: 22Investigation of Carrier Scattering Mechanisms in Tiins2 Single Crystals by Hall Effect Measurements(Wiley-v C H verlag Gmbh, 2004) Qasrawi, AF; Gasanly, NMTlInS2 single crystals are studied through the conductivity and Hall effect measurements in the temperature regions of 100-400 and 170-400 K, respectively. An anomalous behavior of Hall voltage, which changes sign below 315 K, is interpreted through the existence of deep donor impurity levels that behave as acceptor levels when are empty. The hole and electron mobility are limited by the hole- and electron-phonon short range interactions scattering above and below 315 K, respectively. An energy level of 35 meV and a set of donor energy levels located at 360, 280, 220 and 170/152 meV are determined from the temperature dependencies of the carrier concentration and conductivity. A hole, electron, hole-electron pair effective masses of 0.24 in,, 0.14 m(o) and 0.09 m(o) and hole- and electron-phonon coupling constants of 0.50 and 0.64, respectively, are obtained from the Hall effect measurements. The theoretical fit of the Hall coefficient reveals a hole to electron mobility ratio of 0.8. (C) 2004 WILEY-VCH Verlag Gmbh & Co. KGaA, Weinheim.
