Browsing by Subject "Ferroelectricity"
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Item Open Access Ferroelectric based microgyroscope for inertial measurement unit: Modeling and simulation(IEEE, 2012) Ozer, Z.; Mamedov, Amirullah M.; Özbay, EkmelThis paper present the design and modeling of the micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT and Ba xSr 1-xTiO 3) based by using finite element model (FEM) simulation. © 2012 IEEE.Item Open Access Ferroelectric based tuneable SRR based metamaterial for microwave applications(IEEE, 2007) Özbay, Ekmel; Aydın, Koray; Bütün, Serkan; Kolodziejak, K.; Pawlak, D.We discuss the possibility of achieving tunable split ring resonators at microwave frequencies. One method is to use varying capacitance values to tune the magnetic resonance frequency. As another method ferroelectric thin films can be employed to obtain active response from the split ring resonators. We report the experimental measurements that are performed for single split ring resonators at microwave frequencies.Item Open Access Linear and non-linear optical properties of AgBO3(B=Nb, Ta): First principle study(IEEE, 2013) Şimşek, Şevket; Mamedov, Amirullah M.; Özbay, EkmelThe linear and nonlinear optical properties of ferroelectrics AgBO 3 (B=Ta, Nb) are studied by density functional theory (DFT) in the local density approximation (LDA) expressions based on first principle calculations without the scissor approximation. Specially, we present calculations of the frequency-dependent complex dielectric function ε(ω), and the second harmonic generation response coefficient χ(2)(-2ω,ω,ω) over a large frequency range in rhombohedral phase for the first time. The electronic linear electrooptic susceptibility χ(2)(-ω,ω,0) is also evaluated below the band gap. These results are based on a series of the LDA calculation using DFT. © 2013 IEEE.Item Open Access Low-temperature phase transitions in TlGaS2 layer crystals(Pergamon Press, 1993) Aydınlı, Atilla; Ellialtioǧlu, R.; Allakhverdiev, K. R.; Ellialtioǧlu, S.; Gasanly, N. M.Polarized Raman scattering spectra of TlGaS2 layer crystals have been studied for the first time as a function of temperature between 8.5 and 295 K. No evidence for a soft mode behaviour has been found. The anomalies observed in the temperature dependence of low- and high-frequency phonon modes at ∼ 250 and ∼ 180 K, respectively, are explained as due to the phase transitions. It is supposed that the phase transitions are caused by the deformation of structural complexes GaS4, rather than by slippage of Tl atom channels in [110] and [110] directions, which is mainly responsible for the appearance of the low-temperature ferroelectric phase transitions in other representatives of TlBX2 layer compounds. © 1993.Item Open Access Modeling and simulation of the ferroelectric based micro gyroscope: FEM analysis(Taylor and Francis, 2013-09-23) Ozer, Z.; Mamedov, Amirullah M.; Özbay, EkmelThis paper presents the design and modeling of micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT) based by using finite element model (FEM) simulation. The conceptual framework establishes five steps to perform the critical analysis: design a novel structure, define the failure mechanisms under the given conditions, analyze different vibrations, analyze the operation principle, and detect resonance modes. In addition, MEMS failure modes were analyzed under different scenarios and the obtained results discussed. Copyright © Taylor & Francis Group, LLC.Item Open Access One and two dimensional LiNbO3 photonic crystals(IEEE, 2013) Şimşek, Şevket; Mamedov, Amirullah M.; Özbay, EkmelIn this report, we present an investigation of the optical properties and band structure calculations for the photonic crystal structures (PCs) based on one-dimensional (1D) and two-dimensional (2D) ferroelectric LiNbO3 crystal. Here we use 1D and 2D periodic crystal structure of dielectric rods and layers in air background. We have theoretically calculated photonic band structure and optical properties of 1D and 2D LiNbO3 PCs. Beside, we have calculated affect PBG properties of different parameters such as filling fraction and the shape. In order to get photonic gap map, we have calculated the gaps as a function of radius of the rods. We have also investigated the nature of guided modes in line defect waveguide. In our simulation, we employed the finite-difference time domain (FDTD) technique which implies the solution of Maxwell equations with centered finite-difference expressions for the space and time derivatives. © 2013 IEEE.Item Open Access SbSI based photonic crystal superlattices: band structure and optics(IOP, 2015) Şimsek, Ş.; Koç, H.; Palaz, S.; Oltulu, O.; Mamedov, Amirullah M.; Özbay, EkmelIn this work, we present an investigation of the optical properties and band structure calculations for the photonic crystal structures (PCs) based on one-dimensional (1D)-photonic crystal. Here we use 1D SbSI based layers in air background. We have theoretically calculated the photonic band structure and optical properties of SbSI based PC superlattices. In our simulation, we employed the finite-difference time domain (FDTD) technique and the plane wave expansion method (PWE), which implies the solution of Maxwell equations with centered finite-difference expressions for the space and time derivatives.Item Open Access Structural, elastic, and electronic properties of topological insulators: Sb2Te3 and Bi2Te3(IEEE, 2013) Koc H.; Mamedov, Amirullah M.; Özbay, EkmelWe have performed a first principles study of structural, elastic, and electronic properties of rhombohedral Sb2Te3 and Bi 2Te3 compounds using the density functional theory within the local density approximation. The lattice parameters of considered compounds have been calculated. The second-order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, and Debye temperature have also been estimated in the present work. The calculated electronic band structure shows that Sb2Te3 and Bi2Te 3 compounds have a direct forbidden band gap. Our structural estimation and some other results are in agreement with the available experimental and theoretical data. © 2013 IEEE.