2,860 research outputs found
Quantum Transport Characteristics of Lateral pn-Junction of Single Layer TiS3
Using density functional theory and nonequilibrium Greens functions-based
methods we investigated the electronic and transport properties of monolayer
TiS3 pn-junction. We constructed a lateral pn-junction in monolayer TiS3 by
using Li and F adatoms. An applied bias voltage caused significant variability
in the electronic and transport properties of the TiS3 pn-junction. In
addition, spin dependent current-voltage characteristics of the constructed
TiS3 pn-junction were analyzed. Important device characteristics were found
such as negative differential resistance and rectifying diode behaviors for
spin-polarized currents in the TiS3 pn-junction. These prominent conduction
properties of TiS3 pn-junction offer remarkable opportunities for the design of
nanoelectronic devices based on a recently synthesized single-layered material
Ag and Au Atoms Intercalated in Bilayer Heterostructures of Transition Metal Dichalcogenides and Graphene
The diffusive motion of metal nanoparticles Au and Ag on monolayer and
between bilayer heterostructures of transition metal dichalcogenides and
graphene are investigated in the framework of density functional theory. We
found that the minimum energy barriers for diffusion and the possibility of
cluster formation depend strongly on both the type of nanoparticle and the type
of monolayers and bilayers. Moreover, the tendency to form clusters of Ag and
Au can be tuned by creating various bilayers. Tunability of the diffusion
characteristics of adatoms in van der Waals heterostructures holds promise for
controllable growth of nanostructures.Comment: accepted, APL Ma
-AlN-Mg(OH) vdW Bilayer Heterostructure: Tuning the excitonic characteristics
Motivated by recent studies that reported the successful synthesis of
monolayer Mg(OH) [Suslu \textit{et al.}, Sci. Rep. \textbf{6}, 20525
(2016)] and hexagonal (\textit{h}-)AlN [Tsipas \textit{et al}., Appl. Phys.
Lett. \textbf{103}, 251605 (2013)], we investigate structural, electronic, and
optical properties of vertically stacked -AlN and Mg(OH), through
\textit{ab initio} density-functional theory (DFT), many-body quasi-particle
calculations within the GW approximation, and the Bethe-Salpeter equation
(BSE). It is obtained that the bilayer heterostructure prefers the
stacking having direct band gap at the with Type-II band
alignment in which the valance band maximum and conduction band minimum
originate from different layer. Regarding the optical properties, the imaginary
part of the dielectric function of the individual layers and hetero-bilayer are
investigated. The hetero-bilayer possesses excitonic peaks which appear only
after the construction of the hetero-bilayer. The lowest three exciton peaks
are detailedly analyzed by means of band decomposed charge density and the
oscillator strength. Furthermore, the wave function calculation shows that the
first peak of the hetero-bilayer originates from spatially indirect exciton
where the electron and hole localized at -AlN and Mg(OH),
respectively, which is important for the light harvesting applications.Comment: Accepted by Physical Review
Directed Growth of Hydrogen Lines on Graphene: High Throughput Simulations Powered by Evolutionary Algorithm
We set up an evolutionary algorithm combined with density functional
tight-binding (DFTB) calculations to investigate hydrogen adsorption on flat
graphene and graphene monolayers curved over substrate steps. During the
evolution, candidates for the new generations are created by adsorption of an
additional hydrogen atom to the stable configurations of the previous
generation, where a mutation mechanism is also incorporated. Afterwards a
two-stage selection procedure is employed. Selected candidates act as the
parents of the next generation. In curved graphene, the evolution follows a
similar path except for a new mechanism, which aligns hydrogen atoms on the
line of minimum curvature. The mechanism is due to the increased chemical
reactivity of graphene along the minimum radius of curvature line (MRCL) and to
sp bond angles being commensurate with the kinked geometry of hydrogenated
graphene at the substrate edge. As a result, the reaction barrier is reduced
considerably along the MRCL, and hydrogenation continues like a mechanical
chain reaction. This growth mechanism enables lines of hydrogen atoms along the
MRCL, which has the potential to overcome substrate or rippling effects and
could make it possible to define edges or nanoribbons without actually cutting
the material.Comment: 10 pages of main text, 37 pages of supplementary information, 1
supplementary vide
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Spintronic properties of zigzag-edged triangular graphene flakes
Cataloged from PDF version of article.We investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to antiferromagnetic state under bias voltage can, however, terminate the spin polarizing effects for specific flakes. Geometry and size dependent transport properties of graphene flakes may be crucial for spintronic nanodevice applications. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489919
Covariant transport approach for strongly interacting partonic systems
The dynamics of partons, hadrons and strings in relativistic nucleus-nucleus
collisions is analyzed within the novel Parton-Hadron-String Dynamics (PHSD)
transport approach, which is based on a dynamical quasiparticle model for
partons (DQPM) matched to reproduce recent lattice-QCD results - including the
partonic equation of state - in thermodynamic equilibrium. Scalar- and
vector-interaction densities are extracted from the DQPM as well as effective
scalar- and vector-mean fields for the partons. The transition from partonic to
hadronic degrees of freedom is described by covariant transition rates for the
fusion of quark-antiquark pairs or three quarks (antiquarks), respectively,
obeying flavor current-conservation, color neutrality as well as
energy-momentum conservation. Since the dynamical quarks and antiquarks become
very massive close to the phase transition, the formed resonant 'pre-hadronic'
color-dipole states ( or ) are of high invariant mass, too, and
sequentially decay to the groundstate meson and baryon octets increasing the
total entropy. When applying the PHSD approach to Pb+Pb colllisions at 158
AGeV we find a significant effect of the partonic phase on the
production of multi-strange antibaryons due to a slightly enhanced
pair production from massive time-like gluon decay and a larger formation of
antibaryons in the hadronization process.Comment: 12 pages, 6 figures, to be published in the Proceedings of the 26th
Winter Workshop on `Nuclear Dynamics', Ochto Rios, Jamaica, 2-9 January,
2010
Size-dependent alternation of magnetoresistive properties in atomic chains
Cataloged from PDF version of article.Spin-polarized electronic and transport properties of carbon atomic chains are investigated when they are capped with magnetic transition-metal (TM) atoms like Cr or Co. The magnetic ground state of the TM-C-n-TM chains alternates between the ferromagnetic (F) and antiferromagnetic (AF) spin configurations as a function of n. In view of the nanoscale spintronic device applications the desirable AF state is obtained for only even-n chains with Cr; conversely only odd-n chains with Co have AF ground states. When connected to appropriate metallic electrodes these atomic chains display a strong spin-valve effect. Analysis of structural, electronic, and magnetic properties of these atomic chains, as well as the indirect exchange coupling of the TM atoms through non-magnetic carbon atoms are presented. (c) 2006 American Institute of Physics
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