Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Department: search.filters.department.İzmir Institute of Technology. Materials Science and EngineeringPublisher: search.filters.publisher.American Institute of Physics

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Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 9
    Structural, Electronic, and Magnetic Properties of Point Defects in Polyaniline (c3n) and Graphene Monolayers: a Comparative Study
    (American Institute of Physics, 2020) Sevim, Koray; Sevinçli, Haldun; Sevinçli, Haldun; Sevim, Koray; 03.09. Department of Materials Science and Engineering; 04.05. Department of Pyhsics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    The newly synthesized two-dimensional polyaniline (C3N) is structurally similar to graphene and has interesting electronic, magnetic, optical, and thermal properties. Motivated by the fact that point defects in graphene give rise to interesting features, like magnetization in an all carbon material, we perform density functional theory calculations to investigate vacancy and Stone-Wales type point defects in monolayer C3N. We compare and contrast the structural, electronic, and magnetic properties of these defects with those in graphene. While monovacancies and Stone-Wales defects of C3N result in reconstructions similar to those in graphene, divacancies display dissimilar geometrical features. Different from graphene, all vacancies in C3N have metallic character because of altered stoichiometry; those that have low-coordinated atoms have finite magnetic moments. We further investigate the robustness of the reconstructed structures and the changes in the magnetic moments by applying tensile and compressive biaxial strain. We find that, with the advantage of finite bandgap, point defects in C3N are qualified as good candidates for future spintronics applications.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    The Effect of Adsorbates on the Electrical Stability of Graphene Studied by Transient Photocurrent Spectroscopy
    (American Institute of Physics, 2018) Kalkan, Sırrı Batuhan; Aydın, H.; Çelebi, Cem; Çelebi, Cem; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Adsorbate induced variations in the electrical conductivity of graphene layers with two different types of charge carriers are investigated by using the Transient Photocurrent Spectroscopy (TPS) measurement technique. In-vacuum TPS measurements taken for a duration of 5 ks revealed that the adsorption/desorption of atmospheric adsorbates leads to more than a 110% increment and a 45% decrement in the conductivity of epitaxial graphene (n-type) and chemical vapor deposition graphene (p-type) layers on semi-insulating silicon carbide (SiC) substrates, respectively. The graphene layers on SiC are encapsulated and passivated with a thin SiO2 film grown by the Pulsed Electron Deposition method. The measurements conducted for short periods and a few cycles showed that the encapsulation process completely suppresses the time dependent conductivity instability of graphene independent of its charge carrier type. The obtained results are used to construct an experimental model for identifying adsorbate related conductivity variations in graphene and also in other 2D materials with an inherently high surface-to-volume ratio.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Surface Roughness Estimation of Mbe Grown Cdte/Gaas(211)b by Ex-Situ Spectroscopic Ellipsometry
    (American Institute of Physics, 2016) Karakaya, Merve; Bilgilisoy, Elif; Arı, Ozan; Selamet, Yusuf; Bilgilisoy, Elif; Selamet, Yusuf; Karakaya, Merve; 01. Izmir Institute of Technology; 04.05. Department of Pyhsics; 04. Faculty of Science
    Spectroscopic ellipsometry (SE) ranging from 1.24 eV to 5.05 eV is used to obtain the film thickness and optical properties of high index (211) CdTe films. A three-layer optical model (oxide/CdTe/GaAs) was chosen for the ex-situ ellipsometric data analysis. Surface roughness cannot be determined by the optical model if oxide is included. We show that roughness can be accurately estimated, without any optical model, by utilizing the correlation between SE data (namely the imaginary part of the dielectric function, <ϵ2 > or phase angle, ψ) and atomic force microscopy (AFM) roughness. <ϵ2 > and ψ values at 3.31 eV, which corresponds to E1 critical transition energy of CdTe band structure, are chosen for the correlation since E1 gives higher resolution than the other critical transition energies. On the other hand, due to the anisotropic characteristic of (211) oriented CdTe surfaces, SE data (<ϵ2 > and ψ) shows varieties for different azimuthal angle measurements. For this reason, in order to estimate the surface roughness by considering these correlations, it is shown that SE measurements need to be taken at the same surface azimuthal angle. Estimating surface roughness in this manner is an accurate way to eliminate cumbersome surface roughness measurement by AFM.