Physics / Fizik

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

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Author: search.filters.author.İyikanat, FadılPublisher: search.filters.publisher.IOP Publishing Ltd.

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 110
    Citation - Scopus: 109
    Structural, Electronic and Phononic Properties of Ptse2: From Monolayer To Bulk
    (IOP Publishing Ltd., 2018) Kandemir, Ali; Akbalı, Barış; Şahin, Hasan; Badalov, S. V.; Özcan, Mehmet; İyikanat, Fadıl; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    The layer dependent structural, electronic and vibrational properties of the 1T phase of two dimensional (2D) platinum diselenide are investigated by means of state-of-the-art first-principles calculations. The main findings of the study are: (i) monolayer platinum diselenide has a dynamically stable 2D octahedral structure with 1.66 eV indirect band gap, (ii) the semiconducting nature of 1T-PtSe2 monolayers remains unaffected even at high biaxial strains, (iii) top-to-top (AA) arrangement is found to be energetically the most favorable stacking of 1T-PtSe2 layers, (iv) the lattice constant (layer-layer distance) increases (decreases) with increasing number of layers, (v) while monolayer and bilayer 1T-PtSe2 are indirect semiconductors, bulk and few-layered 1T-PtSe2 are metals, (vi) Raman intensity and peak positions of the A1g and Eg modes are found to be highly dependent on the layer thickness of the material, hence; the number of layers of the material can be determined via Raman measurements.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    Hydrogenation-driven phase transition in single-layer TiSe2
    (IOP Publishing Ltd., 2017) İyikanat, Fadıl; Kandemir, Ali; Şahin, Hasan; Senger, Ramazan Tuğrul; Şahin, Hasan; Senger, Ramazan Tuğrul; 04.04. Department of Photonics; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    First-principles calculations based on density-functional theory are used to investigate the effects of hydrogenation on the structural, vibrational, thermal and electronic properties of the charge density wave (CDW) phase of single-layer TiSe2. It is found that hydrogenation of single-layer TiSe2 is possible through adsorption of a H atom on each Se site. Our total energy and phonon calculations reveal that a structural phase transition occurs from the CDW phase to the T d phase upon full hydrogenation. Fully hydrogenated TiSe2 presents a direct gap semiconducting behavior with a band gap of 119 meV. Full hydrogenation also leads to a significant decrease in the heat capacity of single-layer TiSe2.
  • 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; Selamet, Yusuf; Senger, Ramazan Tuğrul; Selamet, Yusuf; Senger, Ramazan Tuğrul; Şahin, Hasan; 04.04. Department of Photonics; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    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: 8
    Citation - Scopus: 10
    Stability, Electronic and Phononic Properties of Ss and 1t Structures of Sitex (x = 1, 2) and Their Vertical Heterostructures
    (IOP Publishing Ltd., 2017) Kandemir, Ali; İyikanat, Fadıl; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    By performing first-principles calculations, we predict a novel, stable single layer phase of silicon ditelluride, 1T-SiTe2, and its possible vertical heterostructures with single layer β-SiTe. Structural optimization and phonon calculations reveal that 1T-SiTe2 structure has a dynamically stable ground state. Further analysis of the vibrational spectrum at the - point shows that single layer 1T-SiTe2 has characteristic phonon modes at 80, 149, 191 and 294 cm-1. Electronic-band structure demonstrates that 1T-SiTe2 phase exhibits a nonmagnetic metallic ground state with a negligible intrinsic spinorbit splitting. Moreover, it is shown that similar structural parameters of 1T-SiTe2 and existing β-SiTe phases allows construction of 1T-β heterostructures with a negligible lattice mismatch. In this regard, it is found that two energetically favorable stacking orders, namely AA and ATB, have distinctive shear and layer breathing phonon modes. It is important to note that the combination of semiconducting β-SiTe and metallic 1T-SiTe2 building blocks forms ultra-thin Schottky barriers that can be used in nanoscale optoelectronic device technologies.