48 research outputs found
Electronic and magnetic properties of V-doped anatase TiO from first principles
We report a first-principles study on the geometric, electronic and magnetic
properties of V-doped anatase TiO. The DFT+U (Hubbard coefficient)
approach predicts semiconductor band structures for TiVO
(x=6.25 and 12.5%), in good agreement with the poor conductivity of samples,
while the standard calculation within generalized gradient approximation fails.
Theoretical results show that V atoms tend to stay close and result in strong
ferromagnetism through superexchange interactions. Oxygen vacancy induced
magnetic polaron could produce long-range ferromagnetic interaction between
largely separated magnetic impurities. The experimentally observed
ferromagnetism in V-doped anatase TiO at room temperature may originate
from a combination of short-range superexchange coupling and long-range bound
magnetic polaron percolation.Comment: 12 pages and 4 figures (to be appeared in PRB as a brief report
Electronic Structures of SiC Nanoribbons
Electronic structures of SiC nanoribbons have been studied by spin-polarized
density functional calculations. The armchair nanoribbons are nonmagnetic
semiconductor, while the zigzag nanoribbons are magnetic metal. The spin
polarization in zigzag SiC nanoribbons is originated from the unpaired
electrons localized on the ribbon edges. Interestingly, the zigzag nanoribbons
narrower than 4 nm present half-metallic behavior. Without the aid of
external field or chemical modification, the metal-free half-metallicity
predicted for narrow SiC zigzag nanoribbons opens a facile way for nanomaterial
spintronics applications.Comment: 10 pages, 5 figure
Quantum Dot in Z-shaped Graphene Nanoribbon
Stimulated by recent advances in isolating graphene, we discovered that
quantum dot can be trapped in Z-shaped graphene nanoribbon junciton. The
topological structure of the junction can confine electronic states completely.
By varying junction length, we can alter the spatial confinement and the number
of discrete levels within the junction. In addition, quantum dot can be
realized regardless of substrate induced static disorder or irregular edges of
the junction. This device can be used to easily design quantum dot devices.
This platform can also be used to design zero-dimensional functional nanoscale
electronic devices using graphene ribbons.Comment: 4 pages, 3 figure
Average Density of States in Disordered Graphene systems
In this paper, the average density of states (ADOS) with a binary alloy
disorder in disordered graphene systems are calculated based on the recursion
method. We observe an obvious resonant peak caused by interactions with
surrounding impurities and an anti-resonance dip in ADOS curves near the Dirac
point. We also find that the resonance energy (Er) and the dip position are
sensitive to the concentration of disorders (x) and their on-site potentials
(v). An linear relation, not only holds when the impurity concentration is low
but this relation can be further extended to high impurity concentration regime
with certain constraints. We also calculate the ADOS with a finite density of
vacancies and compare our results with the previous theoretical results.Comment: 10 pages, 8 figure