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Shi, W.; Pandey, T.; Lindsay, L.; Woods, L.M. |
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Title |
Vibrational properties and thermal transport in quaternary chalcogenides : the case of Te-based compositions |
Type |
A1 Journal article |
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Year |
2021 |
Publication |
Physical review materials |
Abbreviated Journal  |
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Volume |
5 |
Issue |
4 |
Pages |
045401 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Vibrational thermal properties of CuZn2InTe4, AgZn2InTe4, and Cu2CdSnTe4, derived from binary II-VI zinc-blendes, are reported based on first-principles calculations. While the chalcogenide atoms in these materials have the same lattice positions, the cation atom arrangements vary, resulting in different crystal symmetries and subsequent properties. The compositional differences have important effects on the vibrational thermal characteristics of the studied materials, which demonstrate that low-frequency optical phonons hybridize with acoustic phonons and lead to enhanced phonon-phonon scattering and low lattice thermal conductivities. The phonon density of states, mode Gruneisen parameters, and phonon scattering rates are also calculated, enabling deeper insight into the microscopic thermal conduction processes in these materials. Compositional variations drive differences among the three materials considered here; nonetheless, their structural similarities and generally low thermal conductivities (0.5-4 W/mK at room temperature) suggest that other similar II-VI zinc-blende derived materials will also exhibit similarly low values, as also corroborated by experimental data. This, combined with the versatility in designing a variety of motifs on the overall structure, makes quaternary chalcogenides interesting for thermal management and energy conversion applications that require low thermal conductivity. |
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000655931400005 |
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2021-04-01 |
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ISSN |
2475-9953 |
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UA library record; WoS full record; WoS citing articles |
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Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:179140 |
Serial |
7045 |
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Author |
Shafiei, M.; Fazileh, F.; Peeters, F.M.; Milošević, M.V. |
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Title |
Axion insulator states in a topological insulator proximitized to magnetic insulators : a tight-binding characterization |
Type |
A1 Journal article |
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Year |
2022 |
Publication |
Physical review materials |
Abbreviated Journal |
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Volume |
6 |
Issue |
7 |
Pages |
074205-74208 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
The recent discovery of axion states in materials such as antiferromagnetic topological insulators has boosted investigations of the magnetoelectric response in topological insulators and their promise towards realizing dissipationless topological electronics. In this paper, we develop a tight-binding methodology to explore the emergence of axion states in Bi2Se3 in proximity to magnetic insulators on the top and bottom surfaces. The topological protection of the surface states is lifted by a time-reversal-breaking perturbation due to the proximity of a magnetic insulator, and a gap is opened on the surfaces, giving rise to half-quantized Hall conductance and a zero Hall plateau-evidencing an axion insulator state. We developed a real-space tight-binding Hamiltonian for Bi2Se3 using first-principles data. Transport properties of the system were obtained within the Landauer-Buttiker formalism, and we discuss the creation of axion states through Hall conductance and a zero Hall plateau at the surfaces, as a function of proximitized magnetization and corresponding potentials at the surfaces, as well as the thickness of the topological insulator. |
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Wos |
000832387000006 |
Publication Date |
2022-07-21 |
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ISSN |
2475-9953 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.4 |
Times cited |
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Open Access |
OpenAccess |
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Notes |
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Approved |
Most recent IF: 3.4 |
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Call Number |
UA @ admin @ c:irua:189498 |
Serial |
7130 |
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Author |
de Paula Miranda, L. |
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Title |
Electronic transport in two dimensional systems with defects |
Type |
Doctoral thesis |
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Year |
2022 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
104 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Abstract |
The pursuit for the next generation of nanodevices made scientists focus the attention to two dimensional materials. Experimental works of two dimensional materials are hardly free of structural defects, which, in turn, modify drastically the physical properties of its defect-free counterpart. In this work the presence of structural defects is study in two different materials. First, the dependence of the Hall, bend and longitudinal resistances to a perpendicular magnetic field and to vacancy defects in a four-terminal phosphorene single layer Hall bar is investigated. A tight-binding model in combination with the Landauer-Büttiker formalism is used to calculate the energy spectrum, the lead-to-lead transmissions, and the Hall and bend resistances of the system. It is shown that the terminals with zigzag edge orientation are responsible for the absence of quantized plateaus in the Hall resistance and peaks in the longitudinal resistance. A negative bend resistance in the ballistic regime is found due to the presence of high- and low- energy transport modes in the armchair and zigzag terminals, respectively. The system density of states, with single vacancy defects, shows that the presence of in-gap states is proportional to the number of vacancies. Quantized plateaus in the Hall resistance are only formed in a sufficiently clean system. The effects of different kinds of vacancies in the regime where the quantized plateaus are destroyed and a diffusive regime appears in the bend resistance are investigated. Next, we explore effects due to point defect clustering on the electronic and transport properties of bilayer graphene nanoribbons, for AA and AB stacking and zigzag and armchair boundaries, by means of the tight-binding approach and scattering matrix formalism. Evidence of vacancy concentration signatures exhibiting a maximum amplitude and an universality regardless of the system size, stacking and boundary types, in the density of states around the zero-energy level are observed. Our results are explained via the coalescence analysis of the strong sizeable vacancy clustering effect in the system and the breaking of inversion symmetry at high vacancy densities, demonstrating a similar density of states for two equivalent degrees of concentration disorder, below and above the maximum value. |
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Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:191340 |
Serial |
7151 |
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Author |
Dobrota, A.S.; Vlahovic, J.; V. Skorodumova, N.; Pasti, I.A. |
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Title |
First-principles analysis of aluminium interaction with nitrogen-doped graphene nanoribbons – from adatom bonding to various |
Type |
A1 Journal article |
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Year |
2022 |
Publication |
Materials Today Communications |
Abbreviated Journal |
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Volume |
31 |
Issue |
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Pages |
103388-10 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Enhancing aluminium interaction with graphene-based materials is of crucial importance for the development of Al-storage materials and novel functional materials via atomically precise doping. Here, DFT calculations are employed to investigate Al interactions with non-doped and N-doped graphene nanoribbons (GNRs) and address the impact of the edge sites and N-containing defects on the material's reactivity towards Al. The presence of edges does not influence the energetics of Al adsorption significantly (compared to pristine graphene sheet). On the other hand, N-doping of graphene nanoribbons is found to affect the adsorption energy of Al to an extent that strongly depends on the type of N-containing defect. The introduction of edge-NO group and doping with in -plane pyridinic N result in Al adsorption nearly twice as strong as on pristine graphene. Moreover, double n-type doping via N and Al significantly alters the electronic structure of Al,N-containing GNRs. Our results suggest that selectively doped GNRs with pyridinic N can have enhanced Al-storage capacity and could be potentially used for selective Al electrosorption and removal. On the other hand, Al,N-containing GNRs with pyridinic N could also be used in resistive sensors for mechanical deformation. Namely, strain along the longitudinal axis of these dual doped GNRs does not affect the binding of Al but tunes the bandgap and causes more than 700-fold change in the conductivity. Thus, careful defect engineering and selective doping of GNRs with N (and Al) could lead to novel multifunctional materials with exceptional properties. [GRAPHICS] |
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Wos |
000820987400002 |
Publication Date |
2022-03-15 |
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Abbreviated Series Title |
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ISSN |
2352-4928 |
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UA library record; WoS full record |
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Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:189563 |
Serial |
7163 |
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Author |
Jiang, J. |
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Title |
Ginzburg-Landau dynamical simulations on the nonreciprocal transport properties of two-dimensional superconductors |
Type |
Doctoral thesis |
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Year |
2022 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
XII, 79 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Abstract |
The nonreciprocal charge transport property which depends on the polarity of the applied current, such as the diode effect and the rectification effect, is of great importance for both theoretical research and engineering application. The nonreciprocal transport property in superconductors generally requires to break both the spatial inversion symmetry and the time-reversal symmetry, and therefore becomes one of the fundamental issues in superconductivity. Of particular interest, the superconducting diode effect, which exhibits one-way superconductivity, can potentially be applied to dissipationless diode devices, as a consequence has received extensive attention in recent years. In this Ph. D thesis, we simulate vortex dynamics with heat dissipation by numerically solving time-dependent Ginzburg-Landau equations and heat transfer equation. The nonreciprocal transport properties of the following three superconducting systems are studied. We study a superconducting film patterned with a conformal pinning array and find a giant rectification effect which is consistent with the experimental observation. In presence of the funneling effect due to the geometry of the conformal pinning array, Joule heating of the accumulating vortices creates hot spots and drives the sample to the normal state. Meanwhile, the density gradient of vortex does not match the gradient of pinning. The two mechanisms together lead to the giant rectification effect. We study the nonreciprocal charge transport property in a pinning-free superconducting nano-ring. We systematically calculate the response of the ratchet signal to various parameters in both D.C. and A.C. currents. By analyzing the vortex potential, we find that the nonreciprocal transport property is caused by the asymmetry potential barriers for vortex entry and exit. We study a superconductor/nanoscale-magnetic-dot hybrid structure. It takes advantage of the external current to control the nucleation of vortex-antivortex pairs, and can produce superconducting diode effect without applied magnetic fields. Our vortex dynamics simulation details the progress of the superconducting-normal phase transition due to motion of vortex pairs and heat dissipation. The nonreciprocal transport properties of the above three systems are all based on the broken symmetry of spatial inversion, which is caused by the anisotropic pinning array, the asymmetric geometry, and the nonuniform distribution of the magnetic field, respectively. The mechanisms we discuss in this thesis do not require special property of the materials and thus can be applied to any kinds of conventional superconductors. The present studies would provide solid theoretical basis for the future design and application of the dissipationless superconducting devices. |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:188525 |
Serial |
7168 |
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Author |
Magalhães Cunha, S. |
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Title |
Wave-packet dynamics and electronic transport properties in 2D materials |
Type |
Doctoral thesis |
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Year |
2022 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
219 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Abstract |
This piece of work is twofold. First, the time evolution of wave-packets in 2D systems is analyzed by the Split-Operator technique in three different scenarios: in multilayer phosphorene, the transient oscillations in the time-dependent average of position and momentum were observed due to the zitterbewegung effect, and the wave packet propagates non-uniformly along the space deforming itself into an elliptical shape. These results were corroborated by the Green’s function formalism except for large values of the wave-vector and long times; in 2D semiconductor quantum wires (QWs) with anisotropic effective masses and different angle orientations with respect to the anisotropic axis. We have shown that the greater this angle, the smaller is the energy levels spacing implying in an increase of the accessible electronic states. Additionally, for non-null magnetic field, the quantum Hall edge states are significantly affected by the edge orientation. In the anisotropic case damped oscillations in the average values of velocity in both x and y directions where obtained. Theses oscillations are originated by the QW geometry but also from subwavepackets with different momentum orientations, whereas for isotropic QWs the wavepacket disperses without splitting; in the third scenario the split-operator technique was used to study the Landau levels, the wave packet trajectories and velocities of electrons in graphene at low-energy regime described by a modified Dirac equation where the momentum-operator is written in a generalized form as result of applying the position-dependent translation operator formalism (PDTO). In the second part of this thesis, the electronic and tunneling properties of α − T3 lattices were studied. Electrons in these lattices behave analogous to integer-spin Dirac Fermions. The presence of a third atomic site in the unit cell leads to a flat band in the energy spectrum, providing unique electronic and tunneling properties. The presence of a super-periodic potential and the inclusion of symmetry-breaking terms results in deviations of the atomic equivalence between the atomic sites affecting the Dirac points and the band-gap. Small deviations in the equivalence between the atomic sites and the number of barriers change the transmission properties in these lattices. Additionally, new tunneling regions are possible by adjusting the symmetry between the atomic sites and affect the omnidirectional total transmission called super-Klein tunneling observed in these lattices. We compare those results to the tunneling probabilities through regions where the energy spectrum changes from linear with a middle flat band to a hyperbolic dispersion. |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:189191 |
Serial |
7227 |
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Author |
Pandey, T.; Du, M.-H.; Parker, D.S.; Lindsay, L. |
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Title |
Origin of ultralow phonon transport and strong anharmonicity in lead-free halide perovskites |
Type |
A1 Journal article |
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Year |
2022 |
Publication |
Materials Today Physics |
Abbreviated Journal |
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Volume |
28 |
Issue |
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Pages |
100881-10 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
All-inorganic lead-free halide double perovskites offer a promising avenue toward non-toxic, stable optoelec-tronic materials, properties that are missing in their prominent lead-containing counterparts. Their large ther-mopowers and high carrier mobilities also make them promising for thermoelectric applications. Here, we present a first-principles study of the lattice vibrations and thermal transport behaviors of Cs2SnI6 and gamma-CsSnI3, two prototypical compounds in this materials class. We show that conventional static zero temperature density functional theory (DFT) calculations severely underestimate the lattice thermal conductivities (kappa l) of these compounds, indicating the importance of dynamical effects. By calculating anharmonic renormalized phonon dispersions, we show that some optic phonons significantly harden with increasing temperature (T), which reduces the scattering of heat carrying phonons and enhances calculated kappa l values when compared with standard zero temperature DFT. Furthermore, we demonstrate that coherence contributions to kappa l, arising from wave like phonon tunneling, are important in both compounds. Overall, calculated kappa l with temperature-dependent inter-atomic force constants, built from particle and coherence contributions, are in good agreement with available measured data, for both magnitude and temperature dependence. Large anharmonicity combined with low phonon group velocities yield ultralow kappa l values, with room temperature values of 0.26 W/m-K and 0.72 W/m-K predicted for Cs2SnI6 and gamma-CsSnI3, respectively. We further show that the lattice dynamics of these compounds are highly anharmonic, largely mediated by rotation of the SnI6 octahedra and localized modes originating from Cs rattling motion. These thermal characteristics combined with their previously computed excellent electronic properties make these perovskites promising candidates for optoelectronic and room temperature thermoelectric applications. |
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Wos |
000876484300002 |
Publication Date |
2022-10-10 |
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Abbreviated Series Title |
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Edition |
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ISSN |
2542-5293 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
11.5 |
Times cited |
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Open Access |
Not_Open_Access |
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Most recent IF: 11.5 |
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Call Number |
UA @ admin @ c:irua:192139 |
Serial |
7329 |
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Author |
Seyedmohammadzadeh, M.; Sevik, C.; Guelseren, O. |
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Title |
Two-dimensional heterostructures formed by graphenelike ZnO and MgO monolayers for optoelectronic applications |
Type |
A1 Journal article |
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Year |
2022 |
Publication |
Physical review materials |
Abbreviated Journal |
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Volume |
6 |
Issue |
10 |
Pages |
104004-104013 |
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A1 Journal article; Condensed Matter Theory (CMT) |
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Two-dimensional heterostructures are an emerging class of materials for novel applications because of extensive engineering potential by tailoring intriguing properties of different layers as well as the ones arising from their interface. A systematic investigation of mechanical, electronic, and optical properties of possible heterostructures formed by bilayer structures graphenelike ZnO and MgO monolayers is presented. Different functionality of each layer makes these heterostructures very appealing for device applications. ZnO layer is convenient for electron transport in these structures, while MgO layer improves electron collection. At the outset, all of the four possible stacking configurations across the heterostructure are mechanically stable. In addition, stability analysis using phonon dispersion reveals that the AB stacking formed by placing the Mg atom on top of the O atom of the ZnO layer is also dynamically stable at zero temperature. Henceforth, we have investigated the optical properties of these stable heterostructures by applying many-body perturbation theory within the framework of GW approximation and solving the Bethe-Salpeter equation. It is demonstrated that strong excitonic effects reduce the optical band gap to the visible light spectrum range. These results show that this new two-dimensional form of ZnO/MgO heterostructures open an avenue for novel optoelectronic device applications. |
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000877514900005 |
Publication Date |
2022-10-24 |
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ISSN |
2475-9953 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.4 |
Times cited |
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Open Access |
OpenAccess |
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Approved |
Most recent IF: 3.4 |
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Call Number |
UA @ admin @ c:irua:192167 |
Serial |
7346 |
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Author |
Kocabas, T.; Cakir, D.; Gulseren, O.; Ay, F.; Perkgoz, N.K.; Sevik, C. |
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Title |
A distinct correlation between the vibrational and thermal transport properties of group VA monolayer crystals |
Type |
A1 Journal article |
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Year |
2018 |
Publication |
Nanoscale |
Abbreviated Journal |
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Volume |
10 |
Issue |
16 |
Pages |
7803-7812 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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Abstract |
The investigation of thermal transport properties of novel two-dimensional materials is crucially important in order to assess their potential to be used in future technological applications, such as thermoelectric power generation. In this respect, the lattice thermal transport properties of the monolayer structures of group VA elements (P, As, Sb, Bi, PAs, PSb, PBi, AsSb, AsBi, SbBi, P3As1, P3Sb1, P1As3, and As3Sb1) with a black phosphorus like puckered structure were systematically investigated by first-principles calculations and an iterative solution of the phonon Boltzmann transport equation. Phosphorene was found to have the highest lattice thermal conductivity, , due to its low average atomic mass and strong interatomic bonding character. As a matter of course, anisotropic was obtained for all the considered materials, owing to anisotropy in frequency values and phonon group velocities calculated for these structures. However, the determined linear correlation between the anisotropy in the values of P, As, and Sb is significant. The results corresponding to the studied compound structures clearly point out that thermal (electronic) conductivity of pristine monolayers might be suppressed (improved) by alloying them with the same group elements. For instance, the room temperature of PBi along the armchair direction was predicted to be as low as 1.5 W m(-1) K-1, whereas that of P was predicted to be 21 W m(-1) K-1. In spite of the apparent differences in structural and vibrational properties, we peculiarly revealed an intriguing correlation between the values of all the considered materials as = c(1) + c(2)/m(2), in particular along the zigzag direction. Furthermore, our calculations on compound structures clearly showed that the thermoelectric potential of these materials can be improved by suppressing their thermal properties. The presence of ultra-low values and high electrical conductivity (especially along the armchair direction) makes this class of monolayers promising candidates for thermoelectric applications. |
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000431030000054 |
Publication Date |
2018-03-22 |
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2040-3364; 2040-3372 |
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UA library record; WoS full record; WoS citing articles |
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no |
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Call Number |
UA @ admin @ c:irua:193785 |
Serial |
7388 |
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Author |
Yorulmaz, U.; Demiroglu, I.; Cakir, D.; Gulseren, O.; Sevik, C. |
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Title |
A systematicalab-initioreview of promising 2D MXene monolayers towards Li-ion battery applications |
Type |
A1 Journal article |
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Year |
2020 |
Publication |
JPhys Energy |
Abbreviated Journal |
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Volume |
2 |
Issue |
3 |
Pages |
032006 |
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A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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Abstract |
Two-dimensional materials have been attracting increasing interests because of their outstanding properties for Lithium-ion battery applications. In particular, a material family called MXenes (Mn+1Cn, where n = 1, 2, 3) have been recently attracted immense interest in this respect due to their incomparable fast-charging properties and high capacity promises. In this article, we review the state-of-the-art computational progress on Li-ion battery applications of MXene materials in accordance with our systematical DFT calculations. Structural, mechanical, dynamical, and electrical properties of 20 distinct MXene (M: Sc, Ti, V, Cr, Nb, Mo, Hf, Ta, W, and Zr) have been discussed. The battery performances of these MXene monolayers are further investigated by Li-ion binding energies, open circuit voltage values, and Li migration energy barriers. The experimental and theoretical progress up to date demonstrates particularly the potential of non-terminated or pristine MXene materials in Li ion-storage applications. Stability analyses show most of the pristine MXenes should be achievable, however susceptible to the development progress on the experimental growth procedures. Among pristine MXenes, Ti2C, V2C, Sc2C, and Zr2C compounds excel with their high charge/discharge rate prospect due to their extremely low Li diffusion energy barriers. Considering also their higher predicted gravimetric capacities, Sc, Ti, V, and Zr containing MXenes are more promising for their utilization in energy storage applications. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000569868600001 |
Publication Date |
2020-07-16 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2515-7655 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
6.9 |
Times cited |
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Open Access |
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Notes |
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Approved |
Most recent IF: 6.9; 2020 IF: NA |
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Call Number |
UA @ admin @ c:irua:193748 |
Serial |
7399 |
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| Permanent link to this record |
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Author |
Tiwari, S.; Van de Put, M.L.; Sorée, B.; Vandenberghe, W.G. |
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Title |
Ab initio modeling of few-layer dilute magnetic semiconductors |
Type |
P1 Proceeding |
| |
Year |
2021 |
Publication |
International Conference on Simulation of Semiconductor Processes and Devices : [proceedings]
T2 – International Conference on Simulation of Semiconductor Processes and, Devices (SISPAD), SEP 27-29, 2021, Dallas, TX |
Abbreviated Journal |
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Volume |
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Issue |
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Pages |
141-145 |
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Keywords |
P1 Proceeding; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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Abstract |
We present a computational model to model the magnetic structure of two-dimensional (2D) dilute-magnetic-semiconductors (DMS) both the monolayers and multilayers using first-principles density functional theory (DFT), as well as their magnetic phase transition as a function of temperature using Monte-Carlo simulations. Using our method, we model the magnetic structure of bulk, bilayer, and monolayer MoS2 substitutionally doped with Fe atoms. We find that the out-of-plane interaction in bilayer MoS2 is weakly ferromagnetic, whereas in bulk MoS2 it is strongly anti-ferromagnetic. Finally, we show that the magnetic order is more robust in bilayer Fe-doped MoS2 compared to the monolayer and results in a room-temperature FM at an atomic substitution of 14-16%. |
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Thesis |
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Place of Publication |
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Editor |
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Wos |
000766985400034 |
Publication Date |
2021-11-08 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
978-1-6654-0685-7 |
ISBN |
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Additional Links |
UA library record; WoS full record |
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Impact Factor |
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Times cited |
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Open Access |
Not_Open_Access |
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Notes |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:187291 |
Serial |
7401 |
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| Permanent link to this record |
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Author |
Reyntjens, P.D.; Tiwari, S.; Van de Put, M.L.; Sorée, B.; Vandenberghe, W.G. |
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Title |
Ab-initio study of magnetically intercalated Tungsten diselenide |
Type |
P1 Proceeding |
| |
Year |
2020 |
Publication |
International Conference on Simulation of Semiconductor Processes and Devices : [proceedings]
T2 – International Conference on Simulation of Semiconductor Processes and, Devices (SISPAD), SEP 23-OCT 06, 2020 |
Abbreviated Journal |
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Volume |
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Issue |
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Pages |
97-100 |
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Keywords |
P1 Proceeding; Condensed Matter Theory (CMT) |
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Abstract |
We theoretically investigate the effect of intercalation of third row transition metals (Co, Cr, Fe, Mn, Ti and V) in the layers of WSe2. Using density functional theory (DFT), we investigate the structural stability. We also compute the DFT energies of various magnetic spin configurations. Using these energies, we construct a Heisenberg Hamiltonian and perform a Monte Carlo study on each WSe2 + intercalant system to estimate the Curie or Neel temperature. We find ferromagnetic ground states for Ti and Cr intercalation, with Curie temperatures of 31K and 225K, respectively. In Fe-intercalated WSe2, we predict that antiferromagnetic ordering is present up to 564K. For V intercalation, we find that the system exhibits a double phase transition. |
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Corporate Author |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000636981000025 |
Publication Date |
2020-11-02 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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| |
ISSN |
978-4-86348-763-5 |
ISBN |
|
Additional Links |
UA library record; WoS full record |
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Impact Factor |
|
Times cited |
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Open Access |
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Notes |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:178345 |
Serial |
7402 |
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| Permanent link to this record |
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Author |
Siriwardane, E.M.D.; Demiroglu, I.; Sevik, C.; Cakir, D. |
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Title |
Achieving Fast Kinetics and Enhanced Li Storage Capacity for Ti3C2O2 by Intercalation of Quinone Molecules |
Type |
A1 Journal article |
| |
Year |
2019 |
Publication |
ACS applied energy materials |
Abbreviated Journal |
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Volume |
2 |
Issue |
2 |
Pages |
1251-1258 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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Abstract |
Using first-principles calculations, we demonstrated that high lithium storage capacity and fast kinetics are achieved for Ti3C2O2 by preintercalating organic molecules. As a proof-of-concept, two different quinone molecules, namely 1,4-benzoquinone (C6H4O2) and tetrafluoro-1,4-benzoquinone (C6F4O2) were selected as the molecular linkers to demonstrate the feasibility of this interlayer engineering strategy for energy storage. As compared to Ti3C2O2 bilayer without linker molecules, our pillared structures facilitate a much faster ion transport, promising a higher charge/discharge rate for Li. For example, while the diffusion barrier of a single Li ion within pristine Ti3C2O2 bilayer is at least 1.0 eV, it becomes 0.3 eV in pillared structures, which is comparable and even lower than that of commercial materials. At high Li concentrations, the calculated diffusion barriers are as low as 0.4 eV. Out-of-plane migration of Li ions is hindered due to large barrier energy with a value of around 1-1.35 eV. Concerning storage capacity, we can only intercalate one monolayer of Li within pristine Ti3C2O2 bilayer. In contrast, pillared structures offer significantly higher storage capacity. Our calculations showed that at least two layers of Li can be intercalated between Ti3C2O2 layers without forming bulk Li and losing the pillared structure upon Li loading/unloading. A small change in the in-plane lattice parameters (<0.5%) and volume (<1.0%) and ab initio molecular dynamics simulations prove the stability of the pillared structures against Li intercalation and thermal effects. Intercalated molecules avoid the large contraction/expansion of the whole structure, which is one of the key problems in electrochemical energy storage. Pillared structures allow us to realize electrodes with high capacity and fast kinetics. Our results open new research paths for improving the performance of not only MXenes but also other layered materials for supercapacitor and battery applications. |
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Place of Publication |
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Wos |
000459948900037 |
Publication Date |
2019-01-04 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2574-0962 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193759 |
Serial |
7414 |
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| Permanent link to this record |
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Author |
Ozbal, G.; Senger, R.T.; Sevik, C.; Sevincli, H. |
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Title |
Ballistic thermoelectric properties of monolayer semiconducting transition metal dichalcogenides and oxides |
Type |
A1 Journal article |
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Year |
2019 |
Publication |
Physical review B |
Abbreviated Journal |
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| |
Volume |
100 |
Issue |
8 |
Pages |
085415 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Combining first-principles calculations with Landauer-Mittiker formalism, ballistic thermoelectric transport properties of semiconducting two-dimensional transition metal dichalcogenides (TMDs) and oxides (TMOs) (namely MX2 with M = Cr, Mo, W, Ti, Zr, Hf; X = O, S, Se, Te) are investigated in their 2H and 1T phases. Having computed structural, as well as ballistic electronic and phononic transport properties for all structures, we report the thermoelectric properties of the semiconducting ones. We find that 2H phases of four of the studied structures have very promising thermoelectric properties, unlike their 1T phases. The maximum room temperature p-type thermoelectric figure of merit (ZT) of 1.57 is obtained for 2H-HfSe2, which can be as high as 3.30 at T = 800 K. Additionally, 2H-ZrSe2, 2H-ZrTe2, and 2H-HfS2 have considerable ZT values (both nand p-type), that are above 1 at room temperature. The 1T phases of Zr and Hf-based oxides possess relatively high power factors, however their high lattice thermal conductance values limit their ZT values to below 1 at room temperature. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000480389100007 |
Publication Date |
2019-08-12 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9969; 2469-9950 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193773 |
Serial |
7549 |
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| Permanent link to this record |
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Author |
Tiwari, S.; Van de Put, M.L.; Sorée, B.; Vandenberghe, W.G. |
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Title |
Carrier transport in a two-dimensional topological insulator nanoribbon in the presence of vacancy defects |
Type |
P1 Proceeding |
| |
Year |
2018 |
Publication |
International Conference on Simulation of Semiconductor Processes and Devices : [proceedings]
T2 – International Conference on Simulation of Semiconductor Processes and, Devices (SISPAD), SEP 24-26, 2018, Austin, TX |
Abbreviated Journal |
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Volume |
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Issue |
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Pages |
92-96 |
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Keywords |
P1 Proceeding; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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Abstract |
We model transport through two-dimensional topological insulator (TI) nanoribbons. To model the quantum transport, we employ the non-equilibrium Green's function approach. With the presented approach, we study the effect of lattice imperfections on the carrier transport. We observe that the topologically protected edge states of TIs are robust against a high percentage (2%) of vacancy defects. We also investigate tunneling of the edge states in two decoupled TI nanoribbons. |
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Corporate Author |
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Publisher |
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Place of Publication |
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Wos |
000516619300024 |
Publication Date |
2018-12-08 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
978-1-5386-6790-3; 1946-1577; 978-1-5386-6791-0 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:181281 |
Serial |
7579 |
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Author |
De Beule, C. |
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Title |
Confined quantum systems in topological insulator heterostructures |
Type |
Doctoral thesis |
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Year |
2017 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
141 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Place of Publication |
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Wos |
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Publication Date |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
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ISBN |
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Additional Links |
UA library record |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:147217 |
Serial |
7725 |
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| Permanent link to this record |
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Author |
Ozden, A.; Ay, F.; Sevik, C.; Perkgoz, N.K. |
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Title |
CVD growth of monolayer MoS2: Role of growth zone configuration and precursors ratio |
Type |
A1 Journal article |
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Year |
2017 |
Publication |
Japanese journal of applied physics |
Abbreviated Journal |
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Volume |
56 |
Issue |
6s:[1] |
Pages |
06gg05 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Single-layer, large-scale two-dimensional material growth is still a challenge for their wide-range usage. Therefore, we carried out a comprehensive study of monolayer MoS2 growth by CVD investigating the influence of growth zone configuration and precursors ratio. We first compared the two commonly used approaches regarding the relative substrate and precursor positions, namely, horizontal and face-down configurations where facedown approach is found to be more favorable to obtain larger flakes under identical growth conditions. Secondly, we used different types of substrate holders to investigate the influence of the Mo and S vapor confinement on the resulting diffusion environment. We suggest that local changes of the S to Mo vapor ratio in the growth zone is a key factor for the change of shape, size and uniformity of the resulting MoS2 formations, which is also confirmed by performing depositions under different precursor ratios. Therefore, to obtain continuous monolayer films, the S to Mo vapor ratio is needed to be kept within a certain range throughout the substrate. As a conclusion, we obtained monolayer triangles with a side length of 90 mu m and circles with a diameter of 500 mu m and continuous films with an area of 85 0 mu m x 1 cm when the S-to-Mo vapor ratio is optimized. (C) 2017 The Japan Society of Applied Physics |
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Place of Publication |
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Wos |
000401059800003 |
Publication Date |
2017-05-08 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0021-4922; 1347-4065 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193783 |
Serial |
7747 |
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Author |
Yorulmaz, B.; Ozden, A.; Sar, H.; Ay, F.; Sevik, C.; Perkgoz, N.K. |
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Title |
CVD growth of monolayer WS2 through controlled seed formation and vapor density |
Type |
A1 Journal article |
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Year |
2019 |
Publication |
Materials science in semiconductor processing |
Abbreviated Journal |
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Volume |
93 |
Issue |
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Pages |
158-163 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Large area, single layer WS2 has a high potential for use in optoelectrical devices with its high photo-luminescence intensity and low response time. In this work, we demonstrate a systematic study of controlled tungsten disulfide (WS2) monolayer growth using chemical vapor deposition (CVD) technique. With a detailed investigation of process parameters such as H-2 gas inclusion into the main carrier gas, growth temperature and duration, we have gained insight into two-dimensional (2D) WS2 synthesis through controlling the seed formations and the radical vapor density associated with WO3. We confirm that H-2 gas, when included to the carrier gas, is directly involved in WO3 reduction due to its reductive reagent nature, which provides a more effective sulfurization and monolayer formation process. Additionally, by changing the CVD growth configuration, hence, increasing the tungsten related vapor density and confining the reactant radicals, we succeed in realizing larger WS(2 )monolayers, which is still a technological challenge in order to utilize these structures for practical applications. Further optimization of the growth procedure is demonstrated by tuning the growth duration to prevent the excess seed formations and additional layers which will possibly limit the device performance of the monolayer flakes or films when applied. |
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Place of Publication |
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Wos |
000457727300018 |
Publication Date |
2019-01-09 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1369-8001 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193782 |
Serial |
7748 |
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| Permanent link to this record |
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Author |
Polanco, C.A.; Pandey, T.; Berlijn, T.; Lindsay, L. |
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Title |
Defect-limited thermal conductivity in MoS₂ |
Type |
A1 Journal article |
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Year |
2020 |
Publication |
Physical review materials |
Abbreviated Journal |
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Volume |
4 |
Issue |
1 |
Pages |
014004-14009 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
The wide measured range of thermal conductivities (k) for monolayer MoS2 and the corresponding incongruent calculated values in the literature all suggest that extrinsic defect thermal resistance is significant and varied in synthesized samples of this material. Here we present defect-mediated thermal transport calculations of MoS2 using interatomic forces derived from density functional theory combined with Green's function methods to describe phonon-point-defect interactions and a Peierls-Boltzmann formalism for transport. Conductivity calculations for bulk and monolayer MoS2 using different density functional formalisms are compared. Nonperturbative first-principles methods are used to describe defect-mediated spectral functions, scattering rates, and phonon k, particularly from sulfur vacancies (VS), and in the context of the plethora of measured and calculated literature values. We find that k of monolayer MoS2 is sensitive to phonon-VS scattering in the range of experimentally observed densities, and that first-principles k calculations using these densities can explain the range of measured values found in the literature. Furthermore, measured k values for bulk MoS2 are more consistent because VS defects are not as prevalent. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000619240000001 |
Publication Date |
2020-01-16 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2475-9953 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.4 |
Times cited |
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Open Access |
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Notes |
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Approved |
Most recent IF: 3.4; 2020 IF: NA |
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Call Number |
UA @ admin @ c:irua:190510 |
Serial |
7757 |
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| Permanent link to this record |
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Author |
Doevenspeck, J.; Zografos, O.; Gurunarayanan, S.; Lauwereins, R.; Raghavan, P.; Sorée, B. |
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Title |
Design and simulation of plasmonic interference-based majority gate |
Type |
A1 Journal article |
| |
Year |
2017 |
Publication |
AIP advances |
Abbreviated Journal |
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Volume |
7 |
Issue |
6 |
Pages |
065116 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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Abstract |
Major obstacles in current CMOS technology, such as the interconnect bottleneck and thermal heat management, can be overcome by employing subwavelength-scaled light in plasmonic waveguides and devices. In this work, a plasmonic structure that implements the majority (MAJ) gate function is designed and thoroughly studied through simulations. The structure consists of three merging waveguides, serving as the MAJ gate inputs. The information of the logic signals is encoded in the phase of transmitted surface plasmon polaritons (SPP). SPPs are excited at all three inputs and the phase of the output SPP is determined by theMAJof the input phases. The operating dimensions are identified and the functionality is verified for all input combinations. This is the first reported simulation of a plasmonic MAJ gate and thus contributes to the field of optical computing at the nanoscale. (C) 2017 Author(s). |
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Place of Publication |
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Language |
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Wos |
000404621200036 |
Publication Date |
2017-06-23 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2158-3226 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:152632 |
Serial |
7764 |
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| Permanent link to this record |
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Author |
Kocabas, T.; Ozden, A.; Demiroglu, I.; Cakir, D.; Sevik, C. |
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| |
Title |
Determination of Dynamically Stable Electrenes toward Ultrafast Charging Battery Applications |
Type |
A1 Journal article |
| |
Year |
2018 |
Publication |
The journal of physical chemistry letters |
Abbreviated Journal |
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| |
Volume |
9 |
Issue |
15 |
Pages |
4267-4274 |
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| |
Keywords |
A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT) |
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| |
Abstract |
Electrenes, an atomically thin form of layered electrides, are very recent members of the 2D materials family. In this work, we employed first principle calculations to determine stable, exfoliatable, and application-promising 2D electrene materials among possible M2X compounds, where M is a group II-A metal and X is a nonmetal element (C, N, P, As, and Sb). The promise of stable electrene compounds for battery applications is assessed via their exfoliation energy, adsorption properties, and migration energy barriers toward relevant Li, Na, K, and Ca atoms. Our calculations revealed five new stable electrene candidates in addition to previously known Ca2N and Sr2N. Among these seven dynamically stable electrenes, Ba2As, Ba2P, Ba2Sb, Ca2N, Sr2N, and Sr2P are found to be very promising for either K or Na ion batteries due to their extremely low migration energy barriers (5-16 meV), which roughly demonstrates 105 times higher mobility than graphene and two to four times higher mobility than other promising 2D materials such as MXene (Mo2C). |
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Wos |
000440956500020 |
Publication Date |
2018-07-11 |
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Abbreviated Series Title |
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Series Issue |
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Edition |
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ISSN |
1948-7185 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Open Access |
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Notes |
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no |
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Call Number |
UA @ admin @ c:irua:193765 |
Serial |
7779 |
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| Permanent link to this record |
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Author |
Lou, W.-K. |
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| |
Title |
The electrical properties of low low dimensional topological insulators |
Type |
Doctoral thesis |
| |
Year |
2012 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
186 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Additional Links |
UA library record |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:158894 |
Serial |
7858 |
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| Permanent link to this record |
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Author |
Siriwardane, E.M.D.; Karki, P.; Sevik, C.; Cakir, D. |
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Title |
Electronic and mechanical properties of stiff rhenium carbide monolayers: A first-principles investigation |
Type |
A1 Journal article |
| |
Year |
2018 |
Publication |
Applied surface science |
Abbreviated Journal |
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| |
Volume |
458 |
Issue |
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Pages |
762-768 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
In this study, we predicted two new stable metallic Re-C based monolayer structures with a rectangular (r-ReC2) and a hexagonal (h-Re2C) crystal symmetry using first-principle calculations based on density functional theory. Our results obtained from mechanical and phonon calculations and high-temperature molecular dynamic simulations clearly proved the stability of these two-dimensional (2D) crystals. Interestingly, Re-C monolayers in common transition metal carbide structures (i.e. MXenes) were found to be unstable, contrary to expectations. We found that the stable structures, i.e. r-ReC2 and h-Re2C, display superior mechanical properties over the well-known 2D materials. The Young's modulus for r-ReC2 and h-Re2C are extremely high and were calculated as 351 (1310) and 617 (804) N/m (GPa), respectively. Both materials have larger Young's modulus values than the most of the well-known 2D materials. We showed that the combination of the short strong directional p-d bonds, the high coordination number of atoms in the unit-cell and high valence electron density result in strong mechanical properties. Due to its crystal structure, the r-ReC2 monolayer has anisotropic mechanical properties and the crystallographic direction parallel to the C-2 dimers is stiffer compared to perpendicular direction due to strong covalent bonding within C-2 dimers. h-Re2C was derived from the corresponding bulk structure for which we determined the critical thickness for the dynamically stable bulk-derived monolayer structures. In addition, we also investigated the electronic of these two stable structures. Both exhibit metallic behavior and Re-5d orbitals dominate the states around the Fermi level. Due to their ultra high mechanical stability and stiffness, these novel Re-C monolayers can be exploited in various engineering applications. |
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Place of Publication |
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Wos |
000441400000088 |
Publication Date |
2018-07-11 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0169-4332 |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193776 |
Serial |
7875 |
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| Permanent link to this record |
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Author |
Khazaei, M.; Wang, V.; Sevik, C.; Ranjbar, A.; Arai, M.; Yunoki, S. |
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Title |
Electronic structures of iMAX phases and their two-dimensional derivatives: A family of piezoelectric materials |
Type |
A1 Journal article |
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Year |
2018 |
Publication |
Physical review materials |
Abbreviated Journal |
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| |
Volume |
2 |
Issue |
7 |
Pages |
074002 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Recently, a group of MAX phases, (Mo2/3Y1/3)(2)AlC, (Mo2/3Sc1/3)(2)AlC, (W2/3Sc1/3)(2)AlC,(W2/3Y1/3)(2)AlC, and (V-2/3 Zr-1/3)(2)AlC, with in-plane ordered double transition metals, named iMAX phases, have been synthesized. Experimentally, some of these MAX phases can be chemically exfoliated into two-dimensional (2D) single- or multilayered transition metal carbides, so-called MXenes. Accordingly, the 2D nanostructures derived from iMAX phases are named iMXenes. Here we investigate the structural stabilities and electronic structures of the experimentally discovered iMAX phases and their possible iMXene derivatives. We show that the iMAX phases and their pristine, F, or OH-terminated iMXenes are metallic. However, upon 0 termination, (Mo2/3Y1/3)(2)C, (Mo2/3Sc1/3)(2)C, (W2/3Y1/3)(2)C, and (W2/3Sc1/3)(2)C iMXenes turn into semiconductors. Owing to the absence of centrosymmetry, the semiconducting iMXenes may find applications in piezoelectricity. Our calculations reveal that the semiconducting iMXenes possess giant piezoelectric coefficients as large as 45 x 10(-)(10) C/m. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000438354500001 |
Publication Date |
2018-07-12 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2475-9953 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193791 |
Serial |
7876 |
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| Permanent link to this record |
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Author |
Mirzakhani, M.; Zarenia, M.; Vasilopoulos, P.; Peeters, F.M. |
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Title |
Electrostatically confined trilayer graphene quantum dots |
Type |
A1 Journal article |
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Year |
2017 |
Publication |
Physical review B |
Abbreviated Journal |
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Volume |
95 |
Issue |
15 |
Pages |
155434 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
Electrically gating of trilayer graphene (TLG) opens a band gap offering the possibility to electrically engineer TLG quantum dots. We study the energy levels of such quantum dots and investigate their dependence on a perpendicular magnetic field B and different types of stacking of the graphene layers. The dots are modeled as circular and confined by a truncated parabolic potential which can be realized by nanostructured gates or position-dependent doping. The energy spectra exhibit the intervalley symmetry E-K(e) (m) = -E (h)(K') (m) for the electron (e) and hole (h) states, where m is the angular momentum quantum number and K and K' label the two valleys. The electron and hole spectra for B = 0 are twofold degenerate due to the intervalley symmetry E-K (m) = E-K' [-(m + 1)]. For both ABC [alpha = 1.5 (1.2) for large (small) R] and ABA (alpha = 1) stackings, the lowest-energy levels show approximately a R-alpha dependence on the dot radius R in contrast with the 1/R-3 one for ABC-stacked dots with infinite-mass boundary. As functions of the field B, the oscillator strengths for dipole-allowed transitions differ drastically for the two types of stackings. |
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Corporate Author |
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Wos |
000399797200003 |
Publication Date |
2017-04-22 |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9969; 2469-9950 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
6 |
Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:152652 |
Serial |
7878 |
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Author |
Vargas Paredes, A.A. |
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Title |
Emergent phenomena in superconductors in presence of intraband and cross-band pairing |
Type |
Doctoral thesis |
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Year |
2020 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
142 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Abstract |
In this thesis we investigate the emergence of new phenomena in multigap superconductors and multicomponent Ginzburg-Landau theories in the presence of intraband and cross-band pairing. The first part contains a review of emergent phenomena in superconductors with only intraband pairing, in particular the mechanism behind gap resonances which are accompanied by Higgs and Leggett modes. Then we study the gap resonances induced by two-dimensional quantum confinement and describe its spatial profile using the Bogoliubov-de Gennes equations. In the second part we describe the conditions where the cross-band pair formation is feasible. Using the formalism of Green functions we obtain the equations governing the interplay between intraband and cross-band pairing. Also, we derived the Ginzburg-Landau equations considering both intraband and cross-band pairing. Finally, we describe the crossover between the intraband-dominated and crossband-dominated regimes. These two are delimited by a tendency towards a gapless state. When a magnetic field is applied close to the gapless state, we found new arrangements of vortices like square lattices, stripes, labyrinths or of vortex clusters. The experimental signatures and consequences of crosspairing are discussed for MgB2 and Ba0.6K0.4Fe2As2. |
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Wos |
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Additional Links |
UA library record |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:165865 |
Serial |
7899 |
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| Permanent link to this record |
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Author |
Stosic, D. |
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Title |
High-performance Ginzburg-Landau simulations of superconductivity |
Type |
Doctoral thesis |
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Year |
2018 |
Publication |
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Abbreviated Journal |
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Volume |
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Issue |
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Pages |
166 p. |
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Keywords |
Doctoral thesis; Condensed Matter Theory (CMT) |
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Abstract |
Superconductivity is one of the most important discoveries of the last century. With many applications in physics, engineering, and technology, superconductors are crucial to our way of living. Several material and engineering issues however prevent their widespread usage in everyday life. Comprehensive studies are being directed at these materials and their properties to come up with new technologies that will address these challenges and enhance their superconductive capabilities. In this context, numerical modeling plays an important role in the search of new solutions to existing material and engineering issues. The time-dependent Ginzburg-Landau (TDGL) theory is a powerful predictive tool for modeling the macroscopic behavior of superconductors. However most of the numerical algorithms developed so far are incapable of describing many basic properties of real superconducting devices, and are too slow on current hardware for large-scale numerical simulations necessary for their accurate description. Therefore, the purpose of this thesis is to develop high-performing numerical solutions that can correctly describe material features to be used as modeling tools of laboratory experiments. Some important innovations introduced in this work include the numerical modeling of nonrectangular geometrical shapes with complex electrical and insulating components, the inclusion of dynamic heating of the material, and the description of different types of material inhomogeneities. These encompass the principal features necessary for a complete description of the superconductive physics in real material samples. In this thesis a numerical solution is developed for modeling superconducting thin films and used to study the superconductive properties of three experimental configurations: the dynamics of vortex matter in a Corbino disk, the motion of ultrafast vortices in an hourglass-shaped microbridge, and the photon detection process in a meander-patterned nanowire. Moreover, a numerical solution is developed for modeling three-dimensional superconductors which are studied here for the first time in the type-I superconducting regime. These numerical algorithms are optimized to exploit the computational horsepower of graphics processing units (GPUs) and multicore central-processing unit (CPU) clusters such that they can achieve high-performance and be used to model large-scale problems previously impossible on conventional machines. Several computational tools are also designed to assist with the modeling of superconducting devices. These include a numerical library of the TDGL equations, a novel mechanism for the generation of complex geometries, a closed-form solver to conduct numerical simulations, and a graphics user interface (GUI) to visualize the dynamic behavior of superconductors. The contributions in this thesis ultimately push the boundaries on what is possible in state-of-the-art numerical modeling of superconductivity. |
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Additional Links |
UA library record |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:181141 |
Serial |
8034 |
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| Permanent link to this record |
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Author |
Sar, H.; Ozden, A.; Demiroglu, I.; Sevik, C.; Perkgoz, N.K.; Ay, F. |
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Title |
Long-Term Stability Control of CVD-Grown Monolayer MoS2 |
Type |
A1 Journal article |
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Year |
2019 |
Publication |
Physica status solidi: rapid research letters |
Abbreviated Journal |
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Volume |
13 |
Issue |
7 |
Pages |
1800687 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
The structural stability of 2D transition metal dichalcogenide (TMD) formations is of particular importance for their reliable device performance in nano-electronics and opto-electronics. Recent observations show that the CVD-grown TMD monolayers are likely to encounter stability problems such as cracking or fracturing when they are kept under ambient conditions. Here, two different growth configurations are investigated and a favorable growth geometry is proposed, which also sheds light onto the growth mechanism and provides a solution for the stability and fracture formation issues for TMDs specifically for MoS2 monolayers. It is shown that 18 months naturally and thermally aged MoS2 monolayer flakes grown using specifically developed conditions, retain their stability. To understand the mechanism of the structural deterioration, two possible effective mechanisms, S vacancy defects and growth-induced tensile stress, are assessed by the first principle calculations where the role of S vacancy defects in obtaining oxidation resistant MoS2 monolayer flakes is revealed to be rather more critical. Hence, these simulations, time-dependent observations and thermal aging experiments show that durability and stability of 2D MoS2 flakes can be controlled by CVD growth configuration. |
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Wos |
000477671800009 |
Publication Date |
2019-03-18 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1862-6254 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193784 |
Serial |
8184 |
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Author |
Demirtas, M.; Odaci, C.; Perkgoz, N.K.; Sevik, C.; Ay, F. |
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Title |
Low Loss Atomic Layer Deposited Al2O3 Waveguides for Applications in On-Chip Optical Amplifiers |
Type |
A1 Journal article |
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Year |
2018 |
Publication |
IEEE journal of selected topics in quantum electronics |
Abbreviated Journal |
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Volume |
24 |
Issue |
4 |
Pages |
3100508 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
We present the growth and optimization of ultralow loss Si-based Al2O3 planar waveguides, which have a high potential to boost the performance of rare-earth ion doped waveguide devices operating at visible and C-band wavelength ranges. The planar waveguide structures are grown using thermal atomic layer deposition. Systematic characterization of the obtained thin films is performed by spectroscopic ellipsometry, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses, and the optimum parameters are identified. The optical loss measurements for both transverse electric (TE) and transverse magnetic polarized light at 633, 829, and 1549 nm are performed. The lowest propagation loss value of 0.04 +/- 0.02 dB/cm for the Al2O3 waveguides for TE polarization at 1549 nm is demonstrated. |
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Place of Publication |
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Wos |
000431396300001 |
Publication Date |
2018-04-18 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1077-260x |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:193780 |
Serial |
8187 |
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Author |
Avetisyan, A.A.; Ghazaryan, A.V.; Djotyan, A.P.; Kirakosyan, A.A.; Moulopoulos, K. |
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Title |
Magnetoexcitons in semiconductor quantum rings with complicated (Kane's) dispersion law |
Type |
A1 Journal article |
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Year |
2009 |
Publication |
Acta physica Polonica: A: general physics, solid state physics, applied physics
T2 – 4th Workshop on Quantum Chaos and Localisation Phenomena, MAY 22-24, 2009, Polish Acad Sci, Ctr Theoret Phys, Inst Phys, Polish Acad Sci, Ctr Theoret Phys, Inst Phys, War |
Abbreviated Journal |
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Volume |
116 |
Issue |
5 |
Pages |
826-828 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
The influence of the nonparabolicity of charge carriers dispersion law (Kane's dispersion) on a magnetoexciton energy spectrum in InSb quantum rings is theoretically investigated The analytical expression for the energy spectrum of exciton in a narrow-gap semiconductor nanoring in a magnetic field is obtained. The Aharonov – Bohm oscillations in the energy of excited states are studied. |
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Wos |
000273091200015 |
Publication Date |
2016-02-25 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0587-4246 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
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Open Access |
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Notes |
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Approved |
no |
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Call Number |
UA @ admin @ c:irua:172293 |
Serial |
8193 |
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| Permanent link to this record |
