2,847 research outputs found
A method of recognition of hand drawn line patterns
Method of recognition of hand drawn line pattern
Dipole trap model for the metallic state in gated silicon-inversion layers
In order to investigate the metallic state in high-mobility Si-MOS
structures, we have further developed and precised the dipole trap model which
was originally proposed by B.L. Altshuler and D.L. Maslov [Phys. Rev. Lett.\
82, 145 (1999)]. Our additional numerical treatment enables us to drop several
approximations and to introduce a limited spatial depth of the trap states
inside the oxide as well as to include a distribution of trap energies. It
turns out that a pronounced metallic state can be caused by such trap states at
appropriate energies whose behavior is in good agreement with experimental
observations.Comment: 16 pages, 10 figures, submitte
Electrical transport across Au/Nb:SrTiO3 Schottky interface with different Nb doping
We have investigated electron transport in Nb doped SrTiO single crystals
for two doping densities. We find that the resistivity and mobility are
temperature dependent in both whereas the carrier concentration is almost
temperature invariant. We rationalize this using the hydrogenic theory for
shallow donors. Further, we probe electrical transport across Schottky
interfaces of Au on TiO terminated n-type SrTiO. Quantitative analysis
of macroscopic I-V measurements reveal thermionic emission dominated transport
for the low doped substrate whereas it deviates from such behavior for the high
doped substrate. This work is relevant for designing devices to study
electronic transport using oxide-semiconductors.Comment: 10 Pages, 3 Figure
Graphite based Schottky diodes formed on Si, GaAs and 4H-SiC substrates
We demonstrate the formation of semimetal graphite/semiconductor Schottky
barriers where the semiconductor is either silicon (Si), gallium arsenide
(GaAs) or 4H-silicon carbide (4H-SiC). Near room temperature, the forward-bias
diode characteristics are well described by thermionic emission, and the
extracted barrier heights, which are confirmed by capacitance voltage
measurements, roughly follow the Schottky-Mott relation. Since the outermost
layer of the graphite electrode is a single graphene sheet, we expect that
graphene/semiconductor barriers will manifest similar behavior.Comment: 5 pages, 3 figures, 1 tabl
Temperature Dependent Polarity Reversal in Au/Nb:SrTiO3 Schottky Junctions
We have observed temperature-dependent reversal of the rectifying polarity in
Au/Nb:SrTiO3 Schottky junctions. By simulating current-voltage characteristics
we have found that the permittivity of SrTiO3 near the interface exhibits
temperature dependence opposite to that observed in the bulk, significantly
reducing the barrier width. At low temperature, tunneling current dominates the
junction transport due both to such barrier narrowing and to suppressed thermal
excitations. The present results demonstrate that novel junction properties can
be induced by the interface permittivity
A planar Al-Si Schottky Barrier MOSFET operated at cryogenic temperatures
Schottky Barrier (SB)-MOSFET technology offers intriguing possibilities for
cryogenic nano-scale devices, such as Si quantum devices and superconducting
devices. We present experimental results on a novel device architecture where
the gate electrode is self-aligned with the device channel and overlaps the
source and drain electrodes. This facilitates a sub-5 nm gap between the
source/drain and channel, and no spacers are required. At cryogenic
temperatures, such devices function as p-MOS Tunnel FETs, as determined by the
Schottky barrier at the Al-Si interface, and as a further advantage,
fabrication processes are compatible with both CMOS and superconducting logic
technology.Comment: 6 pages, 4 figures, minor changes from the previous version
Analytical device model for graphene bilayer field-effect transistors using weak nonlocality approximation
We develop an analytical device model for graphene bilayer field-effect
transistors (GBL-FETs) with the back and top gates. The model is based on the
Boltzmann equation for the electron transport and the Poisson equation in the
weak nonlocality approximation for the potential in the GBL-FET channel. The
potential distributions in the GBL-FET channel are found analytically. The
source-drain current in GBL-FETs and their transconductance are expressed in
terms of the geometrical parameters and applied voltages by analytical formulas
in the most important limiting cases. These formulas explicitly account for the
short-gate effect and the effect of drain-induced barrier lowering. The
parameters characterizing the strength of these effects are derived. It is
shown that the GBL-FET transconductance exhibits a pronounced maximum as a
function of the top-gate voltage swing. The interplay of the short-gate effect
and the electron collisions results in a nonmonotonic dependence of the
transconductance on the top-gate length.Comment: 12 pages, 7 figure
Mechanism of Ambipolar Field-Effect Carrier Injections in One-Dimensional Mott Insulators
To clarify the mechanism of recently reported, ambipolar carrier injections
into quasi-one-dimensional Mott insulators on which field-effect transistors
are fabricated, we employ the one-dimensional Hubbard model attached to a
tight-binding model for source and drain electrodes. To take account of the
formation of Schottky barriers, we add scalar and vector potentials, which
satisfy the Poisson equation with boundary values depending on the drain
voltage, the gate bias, and the work-function difference. The current-voltage
characteristics are obtained by solving the time-dependent Schr\"odinger
equation in the unrestricted Hartree-Fock approximation. Its validity is
discussed with the help of the Lanczos method applied to small systems. We find
generally ambipolar carrier injections in Mott insulators even if the work
function of the crystal is quite different from that of the electrodes. They
result from balancing the correlation effect with the barrier effect. For the
gate-bias polarity with higher Schottky barriers, the correlation effect is
weakened accordingly, owing to collective transport in the one-dimensional
correlated electron systems.Comment: 21 pages, 10 figures, to appear in J. Phys. Soc. Jp
The impacts of surface conditions on the vapor-liquid-solid growth of germanium nanowires on Si (100) substrate
The impacts of surface conditions on the growth of Ge nanowires on a Si (100) substrate are discussed in detail. On SiO2-terminated Si substrates, high-density Ge nanowires can be easily grown. However, on H-terminated Si substrates, growing Ge nanowires is more complex. The silicon migration and the formation of a native SiO2 overlayer on a catalyst surface retard the growth of Ge nanowires. After removing this overlayer in the HF solution, high-density and well-ordered Ge nanowires are grown. Ge nanowires cross vertically and form two sets of parallel nanowires. It is found that nanowires grew along ?110? direction
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