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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: 1Citation - Scopus: 2Spectroscopic Ellipsometry Studies of Optical Properties of Tlin(s0.25se0.75< Crystal(Springer Heidelberg, 2023) Guler, I.; Isik, M.; Gasanly, N.The optical properties of TlIn(S0.25Se0.75)(2) crystals were studied by ellipsometry measurements. X-ray diffraction pattern presented well-defined peaks associated with monoclinic structure. Energy dependent graphs of various linear optical parameters of the crystal were presented in the 1.25-4.50 eV range. The band gap and Urbach energies of the compound were found as 1.96 and 0.68 eV, respectively, from the analyses of the absorption coefficient. Refractive index spectrum was analyzed considering the single-effective-oscillator model to get oscillator and dispersion energies, zero and high frequency dielectric constants, plasma frequency. Moreover, the nonlinear refractive index, first-order and third-order nonlinear susceptibilities of TlIn(S0.25Se0.75)(2) crystal were revealed in the present paper.Article Citation - WoS: 7Citation - Scopus: 7Effect of Thallium (tl) Substitution for Indium (in) on Ellipsometric Characteristics of Tlinse2 Single Crystals(Elsevier Sci Ltd, 2021) Isik, M.; Gasanly, N. M.TlMeSe2 (Me: Tl, In) semiconducting compounds exhibiting chain structure have been attractive ternary materials in various technological devices. In the TlMeSe2 structure, Tl1+ is monovalent while Me3+ is trivalent ions. The present paper reports the results of spectroscopic ellipsometry measurements performed on Tl1+(Tl0.2In0.8)3+Se2 (abbreviated as Tl1.2In0.8Se2) single crystals which were grown by substituting thallium for indium. The measurements were performed for orientations of E//c and Etc (E: electric field and c: optical axis). The analyses of ellipsometry data considering air-sample optical model presented the spectral dependencies of dielectric function, refractive index and extinction coefficient in the 1.2-5.0 eV range. Critical point energies of studied single crystal were obtained by fitting second-energy derivative spectra of dielectric function. The determined energies were compared with those of TlInSe2 to understand the effect of thalliumindium substitution in the compound. The crystal structure and atomic compositions of the constituent elements were also reported throughout the paper.Article Citation - WoS: 3Citation - Scopus: 3Characterization of Ag/Tlinse2< Structure(Wiley-blackwell, 2011) Qasrawi, A. F.; Gasanly, N. M.In this work, the current voltage characteristics of Ag/TlInSe2/Ag and In/TlInSe2/In structures, the incident light intensity and time dependencies of photocurrent as well as the response time-illumination intensity dependence of Ag/TlInSe2/Ag structures have been studied. For bias voltages larger than 1200. and 4.0 V, the current injection was found to be space charge limited and was assigned to the existing of deep and shallow hole traps being located at 210 and 16 meV for Ag and In-contacted samples, respectively. While indium-contacted samples show S-shaped I-V dependence above bias voltage of 10.0V, silver contacted samples does not show this behavior even at 200.0 V. For the Ag/TlInSe2/Ag structure, photocurrent was observed to exhibit stable values in a very short period of time. The device response time decreases with increasing illumination intensity, it exhibits a value of 0.13 s at incident light intensity of 53.6 mW cm(-2). The decrement in response time with increasing illumination intensity is associated with an increment in photocurrent at the same ratio. The ohmic behavior up to high voltages (120 V), the fast response time and the large spatial photocurrent make the Ag/TlInSe2/Ag structure promising IR detectors. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
