Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

Browse

Filters

20212

Settings

Author: search.filters.author.Akgenç, BernaScopus Q: search.filters.scopusQuartile.Q2

Search Results

Now showing 1 - 2 of 2
  • Article
    Citation - WoS: 21
    Citation - Scopus: 21
    Prediction of Monoclinic Single-Layer Janus Ga2tex (x = S and Se): Strong In-Plane Anisotropy
    (American Physical Society, 2021) Yağmurcukardeş, Mehmet; Moğulkoç, Yeşim; Akgenç, Berna; Moğulkoç Aybey; Peeters, François M.
    By using density functional theory (DFT) based first-principles calculations, electronic, vibrational, piezo-electric, and optical properties of monoclinic Janus single-layer Ga2TeX (X = S or Se) are investigated. The dynamical, mechanical, and thermal stability of the proposed Janus single layers are verified by means of phonon bands, stiffness tensor, and quantum molecular dynamics simulations. The calculated vibrational spectrum reveals the either pure or coupled optical phonon branches arising from Ga-Te and Ga-X atoms. In addition to the in-plane anisotropy, single-layer Janus Ga2TeX exhibits additional out-of-plane asymmetry, which leads to important consequences for its electronic and optical properties. Electronic band dispersions indicate the direct band-gap semiconducting nature of the constructed Janus structures with energy band gaps falling into visible spectrum. Moreover, while orientation-dependent linear-elastic properties of Janus single layers indicate their strong anisotropy, the calculated in-plane stiffness values reveal the ultrasoft nature of the structures. In addition, predicted piezoelectric coefficients show that while there is a strong in-plane anisotropy between piezoelectric constants along armchair (AC) and zigzag (ZZ) directions, there exists a tiny polarization along the out-of-plane direction as a result of the formation of Janus structure. The optical response to electromagnetic radiation has been also analyzed through density functional theory by considering the independent-particle approximation. Finally, the optical spectra of Janus Ga2TeX structures is investigated and it showed a shift from the ultraviolet region to the visible region. The fact that the spectrum is between these regions will allow it to be used in solar energy and many nanoelectronics applications. The predicted monoclinic single-layer Janus Ga2TeX are relevant for promising applications in optoelectronics, optical dichroism, and anisotropic nanoelasticity.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 6
    Tuning the Structural, Electronic and Dynamical Properties of Janus M4x3y3 (m = Pd, Ni and Co; X,y = S, Se and Te) Monolayers: a Dft Study
    (Royal Society of Chemistry, 2021) Eren, İsmail; Akgenç, Berna
    Based on density functional theory, the structural, electronic and vibrational properties of two-dimensional transition metal chalcogenides M2X3 and their Janus type M4X3Y3, where M = Pd, Co and Ni and X = Se, S and Te, are investigated. Motivated by the successful synthesis of a 2D Pd2Se3 monolayer and the proof of the dynamical stability of Ni2Se3 and Co2Se3 monolayers, in terms of the phonon band dispersions, we have systemically studied the fundamental physical properties of Janus transition metal chalcogenides, such as their structural, phonon and thermodynamic stability and their electronic and mechanical properties. Our results show that Janus structures of M4X3Y3 are energetically favorable and dynamically stable. The ab initio molecular dynamic simulations (AIMD) results clearly prove that they kept their thermal stability at room temperature. We have demonstrated their structural, electronic and vibrational properties and Raman spectra. The electronic band dispersions show that monolayer Co2Se3 shows half-metal properties with a moderate band gap (1.01 eV), Pd2Se3 has a 1.42 eV direct band gap, while Ni2Se3 has a 1.38 eV indirect band gap. Pd4Se3S3, Pd4Se3Te3 and Pd4S3Te3 are indirect band gap semiconductors with band gaps of 1.22 eV, 1.05 eV and 0.61 eV, respectively. Ni4Se3S3, Ni4Se3Te3 and Ni4S3Te3 are indirect band gap semiconductors with band gaps of 1.61 eV, 0.77 eV and 0.49 eV, respectively. While pristine Co2Se3 is shown to have half-metallicity (HM), the HM behaviour of the Janus Co4Se3Te3 and Co4S3Te3 monolayers disappear and Co4Se3S3 remains a HM with a moderate band gap of 0.85 eV. In addition, the Raman spectra of these Janus materials are shown to exhibit totally distinctive features as compared to those of the pristine materials. This work reveals the important material properties of Janus type M4X3Y3 monolayers, where M = Pd, Co and Ni and X = Se, S and Te, which could have wide applications in new functional devices.