5,057 research outputs found
Semiconductor-enriched single wall carbon nanotube networks applied to field effect transistors
Substantial progress on field effect transistors "FETs" consisting of
semiconducting single wall carbon nanotubes "s-SWNTs" without detectable traces
of metallic nanotubes and impurities is reported. Nearly perfect removal of
metallic nanotubes is confirmed by optical absorption, Raman measurements, and
electrical measurements. This outstanding result was made possible in
particular by ultracentrifugation (150 000 g) of solutions prepared from SWNT
powders using polyfluorene as an extracting agent in toluene. Such s-SWNTs
processable solutions were applied to realize FET, embodying randomly or
preferentially oriented nanotube networks prepared by spin coating or
dielectrophoresis. Devices exhibit stable p-type semiconductor behavior in air
with very promising characteristics. The on-off current ratio is 10^5, the
on-current level is around 10 A, and the estimated hole mobility is larger
than 2 cm2 / V s
Fictions, Fault, and Forgiveness: Jury Nullification in a New Context
Recently, critics of the Anglo-American jury system have complained that juries in criminal trials have been ignoring the law, in favor of defendants who claim that they lack criminal responsibility because they are afflicted by the various victimization syndromes now popularized in the mass media. In this Article, Professors Dorfman and Iijima counter this characterization of the runaway jury and argue that juries are not ignoring the law, but rather, are exercising a primary power of the jury, to nullify the application of the law when such application to a particular defendant is unjust. The Authors trace the development of the jury nullification power from its beginnings in the late seventeenth century to the present. The Authors then counter the standard arguments against jury nullification. Finally, the Authors propose an explicit jury nullification instruction and accommodating adjustments to other trial procedures that would solve the deficiencies of the current manner in which juries exercise their nullification power
Pressure dependence of the thermoelectric power of single-walled carbon nanotubes
We have measured the thermoelectric power (S) of high purity single-walled
carbon nanotube mats as a function of temperature at various hydrostatic
pressures up to 2.0 GPa. The thermoelectric power is positive, and it increases
in a monotonic way with increasing temperature for all pressures. The low
temperature (T < 40 K) linear thermoelectric power is pressure independent and
is characteristic for metallic nanotubes. At higher temperatures it is enhanced
and though S(T) is linear again above about 100 K it has a nonzero intercept.
This enhancement is strongly pressure dependent and is related to the change of
the phonon population with hydrostatic pressure.Comment: 4 pages, 3 figure
Neutral B Flavor Tagging for the Measurement of Mixing-induced CP Violation at Belle
We describe a flavor tagging algorithm used in measurements of the CP
violation parameter sin2phi_1 at the Belle experiment. Efficiencies and wrong
tag fractions are evaluated using flavor-specific B meson decays into hadronic
and semileptonic modes. We achieve a total effective efficiency of $ 28.8 +-
0.6 %.Comment: 28 pages, 9 figure
Curvature, hybridization, and STM images of carbon nanotubes
The curvature effects in carbon nanotubes are studied analytically as a
function of chirality. The pi-orbitals are found to be significantly
rehybridized in all tubes, so that they are never normal to the tubes' surface.
This results in a curvature induced gap in the electronic band-structure, which
turns out to be larger than previous estimates. The tilting of the pi-orbitals
should be observable by atomic resolution scanning tunneling microscopy
measurements.Comment: Four pages in revtex format including four epsfig-embedded figures.
The latest version in PDF format is available from
http://fy.chalmers.se/~eggert/papers/hybrid.pd
Dimerization structures on the metallic and semiconducting fullerene tubules with half-filled electrons
Possible dimerization patterns and electronic structures in fullerene tubules
as the one-dimensional pi-conjugated systems are studied with the extended
Su-Schrieffer-Heeger model. We assume various lattice geometries, including
helical and nonhelical tubules. The model is solved for the half-filling case
of -electrons. (1) When the undimerized systems do not have a gap, the
Kekule structures prone to occur. The energy gap is of the order of the room
temperatures at most and metallic properties would be expected. (2) If the
undimerized systems have a large gap (about 1eV), the most stable structures
are the chain-like distortions where the direction of the arranged
trans-polyacetylene chains is along almost the tubular axis. The electronic
structures are ofsemiconductors due to the large gap.Comment: submitted to Phys. Rev. B, pages 15, figures 1
Spin configurations of carbon nanotube in a nonuniform external potential
We study, theoretically, the ground state spin of a carbon nanotube in the
presence of an external potential. We find that when the external potential is
applied to a part of the nanotube, its variation changes the single electron
spectrum significantly. This, in combination with Coulomb repulsion and the
symmetry properties of a finite length armchair nanotube induces spin flips in
the ground state when the external potential is varied. We discuss the possible
application of our theory to recent measurements of Coulomb blocked peaks and
their dependence on a weak magnetic field in armchair carbon nanotubes.Comment: RevTeX, 5 pages + two figure
Magnetic Structure of Nano-Graphite Moebius Ribbon
We consider the electronic and magnetic properties of nanographite ribbon
with zigzag edges under the periodic or Moebius boundary conditions. The zigzag
nano-graphite ribbons possess edge localized states at the Fermi level which
cause a ferrimagnetic spin polarization localized at the edge sites even in the
very weak Coulomb interaction. The imposition of the Moebius boundary condition
makes the system non-AB-bipartite lattice, and depress the spin polarization,
resulting in the formation of a magnetic domain wall. The width of the magnetic
domain depends on the Coulomb interaction and narrows with increasing U/t.Comment: 4 pages; 6 figures; published at J. Phys. Soc. Jpn. Vol. 72 No. 5 pp.
998-1001 (2003
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