Atomic and electronic structures of a polar surface of MgO formed on Ag(111) was investigated by using reflection high energy electron diffraction (RHEED), Auger electron spectroscopy, electron energy loss spectroscopy (EELS), and ultraviolet photoemission spectroscopy (UPS). A rather flat unreconstructed polar MgO(111) 1×1 surface could be grown by alternate adsorption of Mg and O2 on Ag(111). The stability of the MgO(111) surface was discussed in terms of interaction between Ag and Mg atoms at the interface, and charge state of the surface atoms. EELS of this surface did not show a band gap region, and finite density of states appeared at the Fermi level in UPS. These results suggest that a polar MgO(111) surface was not an insulating surface but a semiconducting or metallic surface.
The nanographite grains, the diameter of which was around 5 nm, were formed on Pt͑111͒ by exposing the Pt͑111͒ substrate to benzene gas at room temperature and annealing it up to 850 K. The increase of relative number of edge atoms enabled the observation of edge-derived electronic states. The measurement of ultraviolet photoelectron spectroscopy and near edge x-ray absorption fine structure on the nanographite revealed the appearance of the edge state located at the Fermi level.
The atomic and electronic structure of narrow zigzag
nanoribbons
with finite length, consisting of graphene terminated by fluorine
on one side, hexagonal (h) h-BN,
and h-SiC were studied with density functional theory.
It is found that the asymmetry of nanoribbon edges causes a uniform
curvature of the ribbons due to structural stress in the aromatic
ring plane. Narrow graphene nanoribbons terminated with fluorine on
one side demonstrate a considerable out-of-plane bend, suggesting
that the nanoribbon is a fraction of a conical surface. It is shown
that the intrinsic curvature of the narrow nanoribbons destroys the
periodicity and results in a systematic cancellation of the dipole
moment. The in- and out-of-plane curvature of thin arcs allows their
closure in nanorings or cone fragments of giant diameter. Using the
fragment molecular orbital method, we optimized the structure of a
planar giant arc and a closed ring of h-BN with a
diameter of 105 nm.
The structural, magnetic and electronic properties of 2D VX (X = S, Se) monolayers and graphene/VX heterostructures were studied using a DFT+U approach. It was found that the stability of the 1T phases of VX monolayers is linked to strong electron correlation effects. The study of vertical junctions comprising of graphene and VX monolayers demonstrated that interlayer interactions lead to the formation of strong spin polarization of both graphene and VX fragments while preserving the linear dispersion of graphene-originated bands. It was found that the insertion of Mo atoms between the layers leads to n-doping of graphene with a selective transformation of graphene bands keeping the spin-down Dirac cone intact.
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