284 research outputs found
A possible source of spin-polarized electrons: The inert graphene/Ni(111) system
We report on an investigation of spin-polarized secondary electron emission
from the chemically inert system: graphene/Ni(111). An ordered passivated
graphene layer (monolayer of graphite, MG) was formed on Ni(111) surface via
cracking of propylene gas. The spin-polarization of the secondary electrons
obtained from this system upon photoemission is only slightly lower than the
one from the clean Ni surface, but does not change upon large oxygen exposure.
These results suggest to use such passivated Ni(111) surface as a source of
spin-polarized electrons stable against adsorption of reactive gases.Comment: 11 pages, 3 figure
Growth and electronic structure of graphene on semiconducting Ge(110)
The direct growth of graphene on semiconducting or insulating substrates
might help to overcome main drawbacks of metal-based synthesis, like metal-atom
contaminations of graphene, transfer issues, etc. Here we present the growth of
graphene on n-doped semiconducting Ge(110) by using an atomic carbon source and
the study of the structural and electronic properties of the obtained
interface. We found that graphene interacts weakly with the underlying Ge(110)
substrate that keeps graphene's electronic structure almost intact promoting
this interface for future graphene-semiconductor applications. The effect of
dopants in Ge on the electronic properties of graphene is also discussed.Comment: submitted on 06.04.201
Understanding and engineering phonon-mediated tunneling into graphene on metal surfaces
Metal-intercalated graphene on Ir(111) exhibits phonon signatures in
inelastic elec- tron tunneling spectroscopy with strengths that depend on the
intercalant. Extraor- dinarily strong graphene phonon signals are observed for
Cs intercalation. Li interca- lation likewise induces clearly discriminable
phonon signatures, albeit less pronounced than observed for Cs. The signal can
be finely tuned by the alkali metal coverage and gradually disappears upon
increasing the junction conductance from tunneling to con- tact ranges. In
contrast to Cs and Li, for Ni-intercalated graphene the phonon signals stay
below the detection limit in all transport ranges. Going beyond the
conventional two-terminal approach, transport calculations provide a
comprehensive understanding of the subtle interplay between the
graphene{electrode coupling and the observation of graphene phonon
spectroscopic signatures
Electronic and magnetic properties of the graphene-ferromagnet interface
The article presents the work on the investigation of the surface structure
as well as electronic and magnetic properties of graphene layer on a lattice
matched surface of a ferromagnetic material, Ni(111).Comment: accepted in New J. Phy
Local electronic properties of the graphene-protected giant Rashba-split BiAg surface
We report the preparation of the interface between graphene and the strong
Rashba-split BiAg surface alloy and investigatigation of its structure as
well as the electronic properties by means of scanning tunneling
microscopy/spectroscopy and density functional theory calculations. Upon
evaluation of the quasiparticle interference patterns the unpertrubated linear
dispersion for the band of -doped graphene is observed. Our results
also reveal the intact nature of the giant Rashba-split surface states of the
BiAg alloy, which demonstrate only a moderate downward energy shift upon
the presence of graphene. This effect is explained in the framework of density
functional theory by an inward relaxation of the Bi atoms at the interface and
subsequent delocalisation of the wave function of the surface states. Our
findings demonstrate a realistic pathway to prepare a graphene protected giant
Rashba-split BiAg for possible spintronic applications.Comment: text and figures; submitted on 30.12.201
Graphene on Rh(111): STM and AFM studies
The electronic and crystallographic structure of the graphene/Rh(111) moir\'e
lattice is studied via combination of density-functional theory calculations
and scanning tunneling and atomic force microscopy (STM and AFM). Whereas the
principal contrast between hills and valleys observed in STM does not depend on
the sign of applied bias voltage, the contrast in atomically resolved AFM
images strongly depends on the frequency shift of the oscillating AFM tip. The
obtained results demonstrate the perspectives of application atomic force
microscopy/spectroscopy for the probing of the chemical contrast at the
surface.Comment: manuscript and supplementary information; submitted to Appl. Phys.
Lett. on 01.03.201
Electronic structure, imaging contrast and chemical reactivity of graphene moir\'e on metals
Realization of graphene moir\'e superstructures on the surface of 4d and 5d
transition metals offers templates with periodically modulated electron
density, which is responsible for a number of fascinating effects, including
the formation of quantum dots and the site selective adsorption of organic
molecules or metal clusters on graphene. Here, applying the combination of
scanning probe microscopy/spectroscopy and the density functional theory
calculations, we gain a profound insight into the electronic and topographic
contributions to the imaging contrast of the epitaxial graphene/Ir(111) system.
We show directly that in STM imaging the electronic contribution is prevailing
compared to the topographic one. In the force microscopy and spectroscopy
experiments we observe a variation of the interaction strength between the tip
and high-symmetry places within the graphene moir\'e supercell, which determine
the adsorption cites for molecules or metal clusters on graphene/Ir(111).Comment: submitted on Sep, 6th 201
Spin-resolved photoelectron spectroscopy of Fe3O4 - Revisited
Recently Tobin et al (2007 J. Phys.: Condens. Matter 19 315218) reported on the spin-resolved photoemission study of Fe3O4(001) films, claiming magnetite being a case against half-metallicity. In the present communication we re-examine recent spin-resolved photoemission experiments on Fe3O4 and explain why their criticism is unfounded
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