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Article Citation - WoS: 10Citation - Scopus: 11Dispersive Optical Constants of Thermally Deposited Agin5s8< Thin Films(Elsevier Science Sa, 2008) Qasrawi, A. F.Agln(5)S(8) thin films were obtained by the thermal evaporation of Agln(5)S(8) crystals onto ultrasonically cleaned glass substrates. The films are found to exhibit polycrystalline cubic structure. The calculated lattice parameter of the unit cell (a) is 10.78 angstrom. The transmittance data of the as grown films which was recorded at 300 K in the incidence wavelength (lambda) range of 320-1000 nm are used to calculate the refractive, n(lambda). The transmittance and reflectance data are also used to calculate the absorption coefficient of the as grown Agln5S8 thin films. The fundamental absorption edge is found to be corresponding to a direct allowed transitions energy band gap. This band-to-band transition energy is found to be 1.78 eV and it is consistent with that reported for Agln(5)S(8) single crystals. (c) 2007 Elsevier B.V. All rights reserved.Article Citation - WoS: 12Citation - Scopus: 11Investigation of the Structural and Optoelectronic Properties of the Se/Ga2< Heterojunctions(Elsevier Science Sa, 2018) Qasrawi, A. F.In the current study, the structural and optical properties of the Se/Ga2S3 heterojunctions are investigated by means of X-ray diffraction and ultraviolet-visible light spectrophotometry techniques. The optical interface which was prepared by the physical vapor deposition technique, comprises a polycrystalline orthorhombic selenium layer of thickness of 500 nm coated with amorphous layer of 200 nm thick Ga2S3. The top layer is observed to cause yield stress on the Se layer leading to strained type interface. Optically, the evaporation of Ga2S3 onto selenium blue shifted the energy band gap of Se. The conduction and valence band offsets exhibited values of 1.28 and 0.20 eV, respectively. On the other hand, the optical conductivity spectra which were studied and modeled by the Drude-Lorentz approach in the terahertz frequency domain of 275-675 THz revealed enhanced optical conduction parameters. The use of Se as substrate to Ga2S3 enhanced the drift mobility and plasmon frequency of the Ga2S3. The value of the drift mobility reached 64 cm(2)/Vs at plasmon frequency of 2.04 GHz. In addition, the Se/Ga2S3 interface are observed to exhibit high biasing dependent photosensitivity to visible light irradiation. Such properties of this interface nominate it for use in optoelectronics including visible light communications. (C) 2018 Elsevier B.V. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 16Electrical Parameters of Al/Inse Rf Sensors(Iop Publishing Ltd, 2014) Qasrawi, A. F.An Al/InSe/C Schottky device is designed on the surface of amorphous InSe thin films. The device is observed to exhibit a switching property at particular biasing voltages. The 'on/off' current ratio is found to be 7.9 and 9.3 at forward and reverse biasing voltages of 2.0 and 2.25 V, respectively. The 'off' and 'on' operational modes are ascribed to the domination of the tunneling of charged particles through a barrier height of 0.83 eV with a depletion region width of 64 nm and due to the domination of the thermionic emission of charged carriers over a barrier height of 0.53 eV, respectively. In addition, the spectral analysis of the capacitance of the device which was carried in the frequency range of 10.0 k-3.0 GHz reflected dc voltage biasing-dependent high quality resonating peaks. The strongest one appeared at a frequency of 36.8 MHz for a biasing voltage of 0.70 V. Furthermore, the loss tangent of the Al/InSe/C device is found to be of the order of 10(-7) at 3.0 GHz. Consistently, the capacitance-voltage spectra of these sensors reflected pronounced tunability up to 100 MHz. The Al/InSe/C device performance, the switching properties and the quality of the resonance peaks indicate the possibility of using these sensors in RF technology.Article Citation - WoS: 7Citation - Scopus: 7Illumination Effects on the Capacitance Spectra and Signal Quality Factor of Al/Inse Microwave Sensors(Springer, 2013) Qasrawi, A. F.Amorphous indium selenide thin films have been used in the design of a microwave-sensitive Schottky barrier. The illumination effects on the capacitance spectra, on the signal quality factor, and on the capacitance (C)-voltage (V) characteristics of the Al/InSe/C device are investigated. Particular shifts in the amplitude and in the resonance peaks of the capacitance spectra which were studied in the frequency range of 10.0 kHz to 3.0 GHz are observed. While the photoexcitation of these devices increased the capacity level by similar to 1.6 times the original magnitude, the dark quality factor, which was 2.2 x 10(6) at 3.0 GHz, fell to 1.2 x 10(6) when subjected to luminance of 14.7 klux. Analysis of the C-V curves recorded at signal power ranging from wireless local area network (LAN) levels to the maximum output power of third generation (3G) mobiles reflected high tunability of capacitance upon increasing the voltage or power. The tunability of the biased capacitance was much more pronounced in the light than in the dark. The obtained characteristics of the Al/InSe/C sensors indicate their usability in radio and microwave technology.Article Citation - WoS: 10Citation - Scopus: 11Temperature 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: 18Fabrication of Al/Mgo and C/Mgo Tunneling Barriers for Tunable Negative Resistance and Negative Capacitance Applications(Elsevier Science Bv, 2013) Qasrawi, A. F.In this work, the design and characterization of magnesium oxide based tunneling diodes which are produced on Al and InSe films as rectifying substrates are investigated. It was found that when Al thin films are used, the device exhibit tunneling diode behavior of sharp valley at 0.15 V and peak to valley current ratio (PVCR) of 11.4. In addition, the capacitance spectra of the Al/MgO/C device show a resonance peak of negative capacitance (NC) values at 44.7 MHz. The capacitance and resistance-voltage characteristics handled at an ac signal frequency of 100 MHz reflected a build in voltage (V-bi) of 1.29 V and a negative resistance (NR) effect above 2.05 V. This device quality factor (Q)-voltage response is similar to 10(4). When the Al substrate is replaced by InSe thin film, the tunneling diode valley appeared at 1.1 V. In addition, the PVCR, NR range, NC resonance peak, Q and lib; are found to be 135, 0.94-2.24 and 39.0 MHz, similar to 10(5) and 1.34 V, respectively. Due to the wide differential negative resistance and capacitance voltage ranges and due to the response of the C/MgO/InSe/C device at 1.0 GHz, these devices appear to be suitable for applications as frequency mixers, amplifiers, and monostable-bistable circuit elements (MOBILE). (c) 2013 Elsevier B.V. All rights reserved.Article Citation - Scopus: 11Cd-Doping Effects on the Properties of Polycrystalline α-In2Se3 Thin Films(2002) Qasrawi, A.F.Article Citation - WoS: 18Citation - Scopus: 19Temperature Dependence of the Direct Allowed Transitions Band Gap and Optical Constants of Polycrystalline Α-in2se3< Thin Films(Elsevier Science Sa, 2006) Qasrawi, A. F.Polycrystalline alpha-In2Se3 thin films were obtained by the thermal evaporation of alpha-In2Se3 crystals onto glass substrates kept at temperature of 200 degrees C. The temperature dependence of the optical band gap in the temperature region of 300-480 K and the room temperature refractive index, it (lambda), of these films have been investigated. The absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge corresponds to a direct allowed transitions energy gap that exhibits a temperature coefficient of -8.51 x 10(-4) (eV/K). The room temperature n(lambda) which was calculated from the transmittance data allowed the identification of the oscillator strength and energy, static dielectric constant and static refractive index as 20.7 and 2.15 eV, 10.70 and 3.26, respectively. (c) 2006 Elsevier B.V. All rights reserved.Article Citation - WoS: 11Citation - Scopus: 13Fabrication and Characterization of To/Gase Au) Schottky Diodes(Iop Publishing Ltd, 2006) Qasrawi, AF; Department of Electrical & Electronics EngineeringThe optical properties of amorphous GaSe thin films deposited onto tin oxide (TO) coated glass substrates are presented for the purpose of using this material for the fabrication of metal-semiconductor devices. Specifically, the room temperature direct allowed and forbidden transition energy band gaps of glass/TO and glass/TO/GaSe films are estimated and found to exhibit values of 3.95 and 1.95 eV, respectively. The temperature dependence of the energy band gap of the glass/TO/GaSe is also studied in the temperature range of 295 - 450 K by means of optical transmittance and reflectance spectra. This study allowed the identification of the rate of change of the band gap with temperature as -5.0 x 10(-4) eV K-1 and the 0 K energy band gap as 2.1 eV. The above reported optical parameters of the glass/TO/GaSe structure seem to be suitable for semiconductor device production such as solar cell converters, metal - insulator - semiconductor (MIS), metal-oxide-semiconductor (MOS), MOSFET, etc devices. As an application, we have used the glass/TO/GaSe substrate for fabricating Schottky diodes using Ag and Au point contacts. The diodes are characterized by measuring the current (I) - voltage (V) characteristics at room temperature. The I - V curves exhibit rectifying properties. The I-V data analysis in the Schottky region (below 1.0 V) revealed barrier heights of 0.60 and 0.73 eV for Ag and Au point contacts, respectively.Article Citation - WoS: 11Citation - Scopus: 11Dispersive Optical Constants and Temperature-Dependent Band Gap of Cadmium-Doped Indium Selenide Thin Films(Iop Publishing Ltd, 2005) Qasrawi, AF; Department of Electrical & Electronics EngineeringPolycrystalline cadmium-doped indium selenide thin films were obtained by the thermal co-evaporation of alpha-In2Se3 crystals and Cd onto glass substrates kept at a temperature of 200 degrees C. The temperature dependence of the optical band gap in the temperature region of 300-450 K and the room temperature refractive index, n(lambda), of these films have been investigated. The absorption edge shifts to lower energy as temperature increases. The fundamental absorption edge corresponds to a direct energy gap that exhibits a temperature coefficient of -6.14 x 10(-4) eV K-1. The room temperature n(lambda) which was calculated from the transmittance data allowed the identification of the oscillator strength and energy, static and lattice dielectric constants and static refractive index as 20.06 and 3.07 eV, 7.43 and 10.52 and 2.74, respectively.
