Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 7Citation - Scopus: 7Stable 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, HasanEmploying 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: 14Citation - Scopus: 14Quantum-Transport Characteristics of a P–n Junction on Single-Layer Tis3(John Wiley and Sons Inc., 2016) İyikanat, Fadıl; Senger, Ramazan Tuğrul; Peeters, François M.; Şahin, HasanBy using density functional theory and non-equilibrium Green′s function-based methods, we investigated the electronic and transport properties of a TiS3 monolayer p–n junction. We constructed a lateral p–n junction on a TiS3 monolayer using Li and F adatoms. An applied bias voltage caused significant variability in the electronic and transport properties of the TiS3 p–n junction. In addition, the spin-dependent current–voltage characteristics of the constructed TiS3 p–n junction were analyzed. Important device characteristics were found, such as negative differential resistance and rectifying diode behaviors for spin-polarized currents in the TiS3 p–n junction. These prominent conduction properties of the TiS3 p–n junction offer remarkable opportunities for the design of nanoelectronic devices based on a recently synthesized single-layered material.Article Citation - WoS: 105Citation - Scopus: 105Pentagonal 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 TuğrulIn 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.Article Citation - WoS: 69Citation - Scopus: 72Spintronic Properties of Zigzag-Edged Triangular Graphene Flakes(American Institute of Physics, 2010) Şahin, Hasan; Senger, Ramazan Tuğrul; Çıracı, SalimWe investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to antiferromagnetic state under bias voltage can, however, terminate the spin polarizing effects for specific flakes. Geometry and size dependent transport properties of graphene flakes may be crucial for spintronic nanodevice applications. © 2010 American Institute of Physics.Article Citation - WoS: 7Citation - Scopus: 6Hartree-Fock Approximation of Bipolaron State in Quantum Dots and Wires(Springer Verlag, 2010) Senger, Ramazan Tuğrul; Kozal, B.; Chatterjee, A.; Erçelebi, AtillaThe bipolaronic ground state of two electrons in a spherical quantum dot or a quantum wire with parabolic boundaries is studied in the strong electron-phonon coupling regime. We introduce a variational wave function that can conveniently conform to represent alternative ground state configurations of the two electrons, namely, the bipolaronic bound state, the state of two individual polarons, and two nearby interacting polarons confined by the external potential. In the bipolaron state the electrons are found to be separated by a finite distance about a polaron size. We present the formation and stability criteria of bipolaronic phase in confined media. It is shown that the quantum dot confinement extends the domain of stability of the bipolaronic bound state of two electrons as compared to the bulk geometry, whereas the quantum wire geometry aggravates the formation of stable bipolarons. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.