PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7645

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Author: search.filters.author.Kandemir, AliPublisher: search.filters.publisher.IOP Publishing Ltd.

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Now showing 1 - 3 of 3
  • 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: 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.
  • Article
    Citation - WoS: 130
    Citation - Scopus: 135
    Thermal Transport Properties of Mos2 and Mose2 Monolayers
    (IOP Publishing Ltd., 2016) Kandemir, Ali; Yapıcıoğlu, Haluk; Kınacı, Alper; Çalın, Tahir; Sevik, Cem; 01. Izmir Institute of Technology
    The isolation of single- to few-layer transition metal dichalcogenides opens new directions in the application of two-dimensional materials to nanoelectronics. The characterization of thermal transport in these new low-dimensional materials is needed for their efficient implementation, either for general overheating issues or specific applications in thermoelectric devices. In this study, the lattice thermal conductivities of single-layer MoS2 and MoSe2 are evaluated using classical molecular dynamics methods. The interactions between atoms are defined by Stillinger-Weber-type empirical potentials that are developed to represent the structural, mechanical, and vibrational properties of the given materials. In the parameterization of the potentials, a stochastic optimization algorithm, namely particle swarm optimization, is utilized. The final parameter sets produce quite consistent results with density functional theory in terms of lattice parameters, bond distances, elastic constants, and vibrational properties of both single-layer MoS2 and MoSe2. The predicted thermal properties of both materials are in very good agreement with earlier first-principles calculations. The discrepancies between the calculations and experimental measurements are most probably caused by the pristine nature of the structures in our simulations.