35,179 research outputs found
Interaction between graphene and SiO2 surface
With first-principles DFT calculations, the interaction between graphene and
SiO2 surface has been analyzed by constructing the different configurations
based on {\alpha}-quartz and cristobalite structures. The single layer graphene
can stay stably on SiO2 surface is explained based on the general consideration
of configuration structures of SiO2 surface. It is also found that the oxygen
defect in SiO2 surface can shift the Fermi level of graphene down which opens
out the mechanism of hole-doping effect of graphene absorbed on SiO2 surface
observed in experiments.Comment: 17 pages, 7 figure
Standard model plethystics
We study the vacuum geometry prescribed by the gauge invariant operators of the minimal supersymmetric standard model via the plethystic program. This is achieved by using several tricks to perform the highly computationally challenging Molien-Weyl integral, from which we extract the Hilbert series, encoding the invariants of the geometry at all degrees. The fully refined Hilbert series is presented as the explicit sum of 1422 rational functions. We found a good choice of weights to unrefine the Hilbert series into a rational function of a single variable, from which we can read off the dimension and the degree of the vacuum moduli space of the minimal supersymmetric standard model gauge invariants. All data in Mathematica format are also presented
Raman spectroscopy of epitaxial graphene on a SiC substrate
The fabrication of epitaxial graphene (EG) on SiC substrate by annealing has
attracted a lot of interest as it may speed up the application of graphene for
future electronic devices. The interaction of EG and the SiC substrate is
critical to its electronic and physical properties. In this work, Raman
spectroscopy was used to study the structure of EG and its interaction with SiC
substrate. All the Raman bands of EG blue shift from that of bulk graphite and
graphene made by micromechanical cleavage, which was attributed to the
compressive strain induced by the substrate. A model containing 13 x 13
honeycomb lattice cells of graphene on carbon nanomesh was constructed to
explain the origin of strain. The lattice mismatch between graphene layer and
substrate causes the compressive stress of 2.27 GPa on graphene. We also
demonstrate that the electronic structures of EG grown on Si and C terminated
SiC substrates are quite different. Our experimental results shed light on the
interaction between graphene and SiC substrate that are critical to the future
applications of EG.Comment: 20 pages, 5 figure
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