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Investigation of In-Gap Field Enhancement at Terahertz Frequencies for a Metasurface Enhanced Sensor
(Institute of Electrical and Electronics Engineers, 2021) Tugay, Halime; Altan, Hakan; Demirhan, Yasemin; Özyüzer, Lütfi; Sabah, Cumali
The arrangements of subwavelength inclusions in a metasurface can serve as an effective absorber for the terahertz region. When such an absorber is combined with a unique material, the absorption can induce effects that can lead to a change in the materials electrical properties. Vanadium dioxide shows a passive and reversible change from monoclinic insulator phase to metallic tetragonal rutile structure by using external stimuli such as temperature (340K), photo excitation, electric field, mechanical strain or magnetic field [1,2]. Upon absorption of the THz radiation, the high electric fields that are generated inside the gaps of the metasurface can serve as trigger points, as was shown previously using kV strength THz E-fields.
Citation - WoS: 2
Citation - Scopus: 2
Analytical Improvement on the Electromagnetic Scattering From Deformed Spherical Conducting Objects
(Institute of Electrical and Electronics Engineers, 2021) Ateş, Barış; Kuştepeli, Alp; Çetin, Zebih
In this paper, electromagnetic scattering from con-ducting deformed spheres is considered analytically by employing the perturbation method and utilizing Debye potentials. To be able to analyze a wide variety of scattering problems, azimuthal variation is indispensable and therefore the geometries of the scatterers considered in this study do not have rotational symmetry, hence they are dependent on the θ and φ angles in spherical coordinates. Analyses are carried up to the second order explicitly to obtain more accurate results and thus scattered fields are obtained with second order corrections. The coefficients used to determine the scattered field are expressed in terms of Clebsch-Gordan coefficients, which enables one to obtain the results for new geometries only by simple algebraic manipulations. Numerical results and their comparisons are also presented for various deformation functions and parameters. IEEE
Citation - WoS: 13
Noise in Hydrogenated Amorphous Silicon
(Institute of Electrical and Electronics Engineers, 2002) Johanson, Robert E.; Güneş, Mehmet; Kasap, Safa O.
Published work on conductance fluctuations in hydrogenated amorphous silicon is surveyed. There are many reports of 1/f noise. some describing unusual features Such as non-Gaussian statistics. The relative insensitivity to doping and temperature is highlighted. In addition to the 1/f noise. random-telegraph-like noise is often reported. The successes and failures of generation-recombination models for 1 f noise and current filament models for the telegraph noise are summarised.
Citation - WoS: 6
Citation - Scopus: 10
1/F Noise in Hydrogenated Amorphous Silicon-Germanium Alloys
(Institute of Electrical and Electronics Engineers, 2003) Johanson, Robert E.; Güneş, Mehmet; Kasap, Safa O.
Measurements were made of conductance noise of a-Si:H and a-Si 1-xGex:H in two different geometries: one where the current flow is transverse to the surface and the other where it is longitudinal to the surface. Because of the large change in sample resistance between the two geometries, it was not possible to measure both geometries at the same temperature. For both geometries, alloyinzg with up to 40% Ge reduces the noise magnitude by several orders of magnitude over that found in a-Si:H. The decrease is incompatible with several popular noise models. Extrapolating the temperature trends for each geometry shows that it is possible that the noise observed in the transverse samples has the same origin as the higher frequency part of the double power law spectra observed in the longitudinal samples.

Physics / Fizik

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