Physics / Fizik

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

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2015 - 20174

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Author: search.filters.author.Kang, J.

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Stable Ultra-Thin Cdte Crystal: a Robust Direct Gap Semiconductor
    (IOP Publishing Ltd., 2017) İyikanat, Fadıl; Akbalı, Barış; Kang, J.; Senger, Ramazan Tuğrul; Selamet, Yusuf; Şahin, Hasan
    Employing density functional theory based calculations, we investigate structural, vibrational and strain-dependent electronic properties of an ultra-thin CdTe crystal structure that can be derived from its bulk counterpart. It is found that this ultra-thin crystal has an 8-atom primitive unit cell with considerable surface reconstructions. Dynamic stability of the structure is predicted based on its calculated vibrational spectrum. Electronic band structure calculations reveal that both electrons and holes in single layer CdTe possess anisotropic in-plane masses and mobilities. Moreover, we show that the ultra-thin CdTe has some interesting electromechanical features, such as strain-dependent anisotropic variation of the band gap value, and its rapid increase under perpendicular compression. The direct band gap semiconducting nature of the ultra-thin CdTe crystal remains unchanged under all types of applied strain. With a robust and moderate direct band gap, single-layer CdTe is a promising material for nanoscale strain dependent device applications.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 18
    Computing Optical Properties of Ultra-Thin Crystals
    (John Wiley and Sons Inc., 2016) Şahin, Hasan; Torun, Engin; Bacaksız, Cihan; Horzum, Şeyda; Kang, J.; Senger, Ramazan Tuğrul; Peeters, François M.
    An overview is given of recent advances in experimental and theoretical understanding of optical properties of ultra-thin crystal structures (graphene, phosphorene, silicene, MoS2 , MoSe2 , WS2 , WSe2 , h-AlN, h-BN, fluorographene, and graphane). Ultra-thin crystals are atomically thick-layered crystals that have unique properties which differ from their 3D counterpart. Because of the difficulties in the synthesis of few-atom-thick crystal structures, which are thought to be the main building blocks of future nanotechnology, reliable theoretical predictions of their electronic, vibrational, and optical properties are of great importance. Recent studies revealed the reliable predictive power of existing theoretical approaches based on density functional theory.
  • Article
    Citation - WoS: 22
    Citation - Scopus: 22
    Electronic and Magnetic Properties of 1t-Tise2 Nanoribbons
    (IOP Publishing Ltd., 2015) Özaydın, H. Duygu; Şahin, Hasan; Kang, J.; Peeters, François M.; Şenger, Ramazan Tuğrul
    Motivated by the recent synthesis of single layer TiSe2,we used state-of-the-art density functional theory calculations, to investigate the structural and electronic properties of zigzag and armchairedged nanoribbons (NRs) of this material. Our analysis reveals that, differing from ribbons of other ultra-thin materials such as graphene, TiSe2 NRs have some distinctive properties. The electronic band gap of the NRs decreases exponentially with the width and vanishes for ribbons wider than 20 Å. For ultranarrow zigzag-edged NRs we find odd-even oscillations in the band gap width, although their band structures show similar features. Moreover, our detailed magnetic-ground-state analysis reveals that zigzag and arm chair edged ribbons have non-magnetic ground states. Passivating the dangling bonds with hydrogen at the edges of the structures influences the band dispersion. Our results shed light on the characteristic properties of T phase NRs of similar crystal structures.
  • Article
    Citation - WoS: 105
    Citation - Scopus: 105
    Pentagonal Monolayer Crystals of Carbon, Boron Nitride, and Silver Azide
    (American Institute of Physics, 2015) Yağmurcukardeş, Mehmet; Şahin, Hasan; Kang, J.; Torun, E.; Peeters, François M.; Senger, Ramazan Tuğrul
    In this study, we present a theoretical investigation of structural, electronic, and mechanical properties of pentagonal monolayers of carbon (p-graphene), boron nitride (p-B2N4 and p-B4N2), and silver azide (p-AgN3) by performing state-of-the-art first principles calculations. Our total energy calculations suggest feasible formation of monolayer crystal structures composed entirely of pentagons. In addition, electronic band dispersion calculations indicate that while p-graphene and p-AgN3 are semiconductors with indirect bandgaps, p-BN structures display metallic behavior. We also investigate the mechanical properties (in-plane stiffness and the Poisson's ratio) of four different pentagonal structures under uniaxial strain. p-graphene is found to have the highest stiffness value and the corresponding Poisson's ratio is found to be negative. Similarly, p-B2N4 and p-B4N2 have negative Poisson's ratio values. On the other hand, the p-AgN3 has a large and positive Poisson's ratio. In dynamical stability tests based on calculated phonon spectra of these pentagonal monolayers, we find that only p-graphene and p-B2N4 are stable, but p-AgN3 and p-B4N2 are vulnerable against vibrational excitations.