99 research outputs found
Magnetotransport in graphene on silicon side of SiC
We have studied the transport properties of graphene grown on silicon side of
SiC. Samples under study have been prepared by two different growth methods in
two different laboratories. Magnetoresistance and Hall resistance have been
measured at temperatures between 4 and 100 K in resistive magnet in magnetic
fields up to 22 T. In spite of differences in sample preparation, the field
dependence of resistances measured on both sets of samples exhibits two periods
of magneto-oscillations indicating two different parallel conducting channels
with different concentrations of carriers. The semi-quantitative agreement with
the model calculation allows for conclusion that channels are formed by
high-density and low-density Dirac carriers. The coexistence of two different
groups of carriers on the silicon side of SiC was not reported before.Comment: 5 pages, 6 figures, accepted for publication in the "IOP Journal of
Physics: Conference series" as a contribution to the proceedings of the 20th
International Conference on "High Magnetic Fields in Semiconductor Physics",
HMF 2
Polarization selection rules for inter-Landau level transitions in epitaxial graphene revealed by infrared optical Hall effect
We report on polarization selection rules of inter-Landau level transitions
using reflection-type optical Hall effect measurements from 600 to 4000 cm-1 on
epitaxial graphene grown by thermal decomposition of silicon carbide. We
observe symmetric and anti-symmetric signatures in our data due to polarization
preserving and polarization mixing inter-Landau level transitions,
respectively. From field-dependent measurements we identify that transitions in
decoupled graphene mono-layers are governed by polarization mixing selection
rules, whereas transitions in coupled graphene mono-layers are governed by
polarization preserving selection rules. The selection rules may find
explanation by different coupling mechanisms of inter-Landau level transitions
with free charge carrier magneto-optic plasma oscillations
Size confinement effect in graphene grown on 6H-SiC (0001) substrate
We have observed the energy structure in the density of occupied states of
graphene grown on n-type 6H-SiC (0001). The structure revealed with
photoelectron spectroscopy is described by creation of the quantum well states
whose number and the energy position (E1 = 0.3 eV, E2 = 1.2 eV, E3 = 2.6 eV )
coincide with the calculated ones for deep (V = 2.9 eV) and narrow (d = 2.15 A)
quantum well formed by potential relief of the valence bands in the structure
graphene/n-SiC. We believe that the quantum well states should be formed also
in graphene on dielectric and in suspended graphene.Comment: 7 pages, 4 figure
Structural characterization of ZnO nanopillars grown by atmospheric-pressure metalorganic chemical vapor deposition on vicinal 4H-SiC and SiO 2
Hybrid multicyclophanes based on thiacalix[4]arene and pillar[5]arene: Synthesis and influence on the formation of polyaniline
© 2018 the Partner Organisations. For the first time, fragments of a pillar[5]arene were spatially preorganized with a thiacalix[4]arene core in a single multimacrocyclic structure. It was shown that the synthesized hybrid multicyclophanes bind aniline and do not interact with p-toluenesulfonic acid. Supramolecular assistance of the synthesized multicyclophanes in oxidative polymerization of aniline in aqueous p-toluenesulfonic acid solutions was studied. It was found that the use of the multicyclophane template in the reaction of the oxidative polymerization of aniline led to the formation of emeraldine with a higher molecular weight and a similar conductivity (1-2 mSm cm-1), which formed more stable emeraldine dispersions in acetone in comparison with traditionally obtained polyaniline
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