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Article Citation - WoS: 2Citation - Scopus: 1Hydrogen Implantation Effects on the Electrical and Optical Properties of Inse Thin Films(Tubitak Scientific & Technological Research Council Turkey, 2012) Qasrawi, Atef Fayez; Ilaiwi, Khaled Faysal; Polimeni, AntonioThe effects of hydrogen ion implantation on the structural, electrical and optical properties of amorphous InSe thin films have been investigated. X-ray diffraction analysis revealed no change in the structure of the films. An implantation of 7.3 x 10(18) ions/cm(2) decreased the electrical conductivity by three orders of magnitude at 300 K. Similarly, the conductivity activation energy, which was calculated in the temperature range of 300-420 K, decreased from 210 to 78 meV by H-ion implantation. The optical measurements showed that the direct allowed transitions energy band gap of amorphous InSe films has decreased from 1.50 to 0.97 eV by implantation. Furthermore, significant decreases in the dispersion and oscillator energy, static refractive index and static dielectric constants are also observed by hydrogen implantation.Article Citation - WoS: 10Citation - Scopus: 10Temperature effects on the optoelectronic properties of AgIn5S8 thin films(Elsevier Science Sa, 2011) Qasrawi, A. F.Polycrystalline AgIn5S8 thin films are obtained by the thermal evaporation of AgIn5S8 crystals onto ultrasonically cleaned glass substrates under a pressure of similar to 1.3 x 10(-3) Pa. The temperature dependence of the optical band gap and photoconductivity of these films was studied in the temperature regions of 300-450 K and 40-300 K, respectively. The heat treatment effect at annealing temperatures of 350, 450 and 550 K on the temperature dependent photoconductivity is also investigated. The absorption coefficient, which was studied in the incidence photon energy range of 1.65-2.55 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge which corresponds to a direct allowed transition energy band gap of 1.78 eV exhibited a temperature coefficient of -3.56 x 10(-4) eV/K. The 0 K energy band gap is estimated as 1.89 eV. AgIn5S8 films are observed to be photoconductive. The highest and most stable temperature invariant photocurrent was obtained at an annealing temperature of 550 K. The photoconductivity kinetics was attributed to the structural modifications caused by annealing and due to the trapping-recombination centers' exchange. (C) 2010 Elsevier B.V. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 18Heat Treatment Effects on the Structural and Electrical Properties of Thermally Deposited Agin5s8< Thin Films(Pergamon-elsevier Science Ltd, 2011) Qasrawi, A. F.; Kayed, T. S.; Ercan, FilizThe heat treatment effects on structural and electrical properties of thermally deposited AgIn5S8 thin films have been investigated. By increasing the annealing temperature of the sample from 450 to 500 K, we observed a change in the crystallization direction from (420) to (311). Further annealing of the AgIn5S8 films at 550, 600 and 650 K resulted in larger grain size in the (311) preferred direction. The room temperature electrical resistivity, Hall coefficient and Hall mobility were significantly influenced by higher annealing temperatures. Three impurity levels at 230, 150, and 78 meV were detected for samples annealed at 350 K. The electrical resistivity decreased by four orders of magnitude when the sample annealing temperature was raised from 350 to 450 K. The temperature dependent electrical resistivity and carrier concentration of the thin film samples were studied in the temperature ranges of 25-300 K and 140-300 K, respectively. A degenerate-nondegenerate semiconductor transition at approximately 180 was observed for samples annealed at 450 and 500 K. Similar type of transition was observed at 240 K for samples annealed at 600 and 650 K. (C) 2011 Elsevier Ltd. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 10Light Intensity Effects on Electrical Properties of Agin5s8< Thin Films(Elsevier Science Sa, 2011) Qasrawi, A. F.The light illumination effects on the current conduction mechanism in thermally annealed polycrystalline AgIn5S8 thin films has been investigated by means of dark and photoexcited conductivity measurements as a function of temperature. The dark electrical conductivity analysis in the temperature region of 30-300 K, reflected the domination of thermionic emission and variable range hopping of charge carriers over the grain boundaries above and below 90 K, respectively. Conductivity activation energies of similar to 155 and 78 meV (in the temperature regions of 230-300 K and 90-220 K. respectively), a density of localized states (evaluated assuming a localization length of 5A(0)) of 1.17 x 10(20) cm(-3) eV(-1), an average hopping distance of 41.51 A(0) (at 60 K) and an average hopping energy of 28.64 meV have been determined from the dark electrical measurements. When the sample was exposed to illumination at specific excitation intensity, the values of the conductivity activation energy, the average hopping energy and the average hopping range were decreased significantly. On the other hand, the density of localized states near the Fermi level increased when the light intensity was increased. Such behavior is attributed to the temporary shift in Fermi level and/or trap density reduction by electron-hole recombination. (C) 2011 Elsevier B.V. All rights reserved.
