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Article Citation - WoS: 2Citation - Scopus: 2Properties of Tl4se3< Single Crystals and Characterization of Ag/Tl4< Schottky Barrier Diodes(Elsevier Science Bv, 2010) Qasrawi, A. F.; Gasanly, N. M.The main physical properties of Tl4Se3S single crystals were investigated for the first time. Particularly, the crystal data, Debye temperature, dark electrical resistivity and Hall effect in addition to the temperature dependent current-voltage characteristics and photosensitivity of the Ag/Tl4Se3S Schottky barrier diode were studied. The X-ray diffraction patterns have revealed that the crystal exhibited a single phase of tetragonal structure belonging to the D-4h(18) - 14mcm space group. A Debye temperature of 100 K was calculated using the results of the X-ray diffraction analysis. The dark electrical resistivity and Hall-effect measurements indicated that the samples exhibits p-type conduction with an electrical resistivity, carrier concentration and Hall mobility of 6.20 x 10(3) Omega cm, 1.16 x 10(12) cm(-3) and 873 cm(2) V-1 s(-1), respectively. The crystals were observed to have Schottky diode properties. The Ag/Tl4Se3S Schottky barrier device bias voltage was observed to depend on the crystal direction and on temperature. It was found that the calculated energy barrier height decreased and the diode ideality factor increased with temperature decreasing. The photosensitivity-light intensity dependence of this device was found to be linear reflecting the ability of using it in optoelectronics. (C) 2009 Elsevier B.V. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 9Investigation of the Electrical Parameters of Ag/P-tlgases Schottky Contacts(Elsevier, 2012) Qasrawi, A. F.; Gasanly, N. M.p-type TlGaSeS single crystal was used to fabricate a Schottky device. Silver and carbon metals were used as the Ohmic and Schottky contacts, respectively. The device which displayed wide RF band at 13.200 and narrow band at 62.517 kHz with Q value of 1.4 and of 6.3 x 10(4), respectively, is characterized by means of current (I)-voltage (V), capacitance (C)-voltage characteristics as well as capacitance-frequency (f) characteristics. The device series resistance, ideality factor and barrier height are determined from the I-Vcurve as 35.8 M Omega, 1.2 and 0.74 eV, respectively. The apparent acceptor density and the build in voltage of the device increased with increasing ac signal frequency. The high Q value, observed at 62.517 kHz. indicated a much lower rate of energy loss relative to the stored energy of the device. The energy loss (Q(-1)) is much less than 0.001% of the stored value. The device was tested and found to remain at the same mode of resonance for several hours. It never switched or ceased unless it was tuned off. (c) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 12Citation - Scopus: 12Design and Characterization of Tlinse2 Varactor Devices(Elsevier, 2011) Qasrawi, A. F.; Aljammal, Faten G.; Taleb, Nisreen M.; Gasanly, N. M.TlInSe2 single crystal has been successfully prepared by the Bridgman crystal growth technique. The crystal, which exhibits compositional atomic percentages of 25.4%, 25.2% and 49.4% for TI, In and Se, respectively, is found to be of tetragonal structure with lattice parameters of a=0.8035 and c=0.6883 nm. The crystals were used to design radio frequency sensitive varactor device. The temperature dependence of the current-voltage characteristics of the device allowed the calculation of the room temperature barrier height and ideality factor as 0.87 eV and as 3.2, respectively. Rising the device temperature increased the barrier height and decreased the ideality factor. This behavior was attributed to the current transport across the metal-semiconductor interface. The capacitance of the device is observed to increase with increasing voltage and increasing temperature as well. The temperature activation of the capacitance starts above 82 degrees C with a temperature coefficient of capacitance being 1.08 x 10 (3) K (1). Furthermore, the capacitance of the device was observed to increase with increasing frequency up to a maximum critical frequency of 4.0 kHz, after which the capacitance decreased with increasing frequency. The behavior reflected the ability of maximum amount of charge holding being at a 4.0 kHz. The analysis of the capacitance-voltage characteristics at fixed frequencies reflected a frequency dependent barrier height and acceptors density. The decrease in the barrier height and acceptors density with increasing frequency is mainly due to the inability of the free charge to follow the ac signal. (C) 2011 Elsevier B.V. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Current Transport Mechanism in Au-p-mgo-ni Schottky Device Designed for Microwave Sensing(Natl inst Optoelectronics, 2016) Qasrawi, A. F.; Khanfar, H. K.; Department of Electrical & Electronics EngineeringAu/MgO/Ni back to back Schottky tunnelling barriers are designed on the surface of an MgO thin layer and are electrically characterized. The current voltage curve analysis has shown that thermionic emission, field effect thermionic (FET) emission and space charge limited current are dominant transport mechanism in distinct biasing regions. It was shown that, while the device is reverse biased with voltages less than 0.31 V, it conducts by tunnelling (FED though an energy barrier of 0.88 eV with a depletion region width of 15.7 nm. As the voltage exceeds 0.46 V, the tunnelling energy barrier is lowered to 0.76 eV and the depletion region widens and arrives at the reach-through running mode. The device was tested in the microwave electromagnetic power range that extends from Bluetooth to WLAN radiation levels at oscillating frequencies of 0.5 and 2.9 GHz. In addition, a low power resonating signal that suits mobile data is superimposed in the device. It was observed that the Au/MgO/Au sensors exhibit a wide tunability range via voltage biasing or via frequency control. The signal quality factor is 3.53 x 10(3) at 2.9 GHz. These properties reflect applicability in microwave technology as wireless and connectorized microwave amplifiers, microwave resonators and mixers.Conference Object Citation - WoS: 2Citation - Scopus: 2Temperature-Dependent Capacitance-Voltage Biasing of the Highly Tunable Tlgate2 Crystals(Elsevier Science Bv, 2012) Qasrawi, A. F.; Gasanly, N. M.The temperature effects on the capacitance-voltage characteristics as well as the room temperature capacitance-frequency characteristics of TlGaTe2 crystals are investigated. A very wide range of linearly varying tunable capacitance from 6.0 mu F to 60 pF was recorded. The capacitance-voltage characteristics, being recorded in the temperature range of 290-380 K, revealed a linear increase in the build in voltage associated with exponential decrease in the density of non-compensated ionized carriers with increasing temperature. The high temperature (up to 380 K) biasing ability, the linear tunability and the high dielectric constant values ( similar to 10(3)) make the TlGaTe2 crystals applicable in microelectronic components. (C) 2012 Elsevier B.V. All rights reserved.
