5,579 research outputs found
Real time image subtraction and "exclusive or" operation using a self-pumped phase conjugate mirror
Real time "exclusive or" operation with an interferometer using a self-pumped phase conjugate mirror is reported. Also, results of image subtraction and intensity inversion are shown
Electronic Interface Reconstruction at Polar-Nonpolar Mott Insulator Heterojunctions
We report on a theoretical study of the electronic interface reconstruction
(EIR) induced by polarity discontinuity at a heterojunction between a polar and
a nonpolar Mott insulators, and of the two-dimensional strongly-correlated
electron systems (2DSCESs) which accompany the reconstruction. We derive an
expression for the minimum number of polar layers required to drive the EIR,
and discuss key parameters of the heterojunction system which control 2DSCES
properties. The role of strong correlations in enhancing confinement at the
interface is emphasized.Comment: 7 pages, 6 figures, some typos correcte
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
First-Principles Study on Leakage Current through Si/SiO Interface
The relationship between the presence of defects at the stacking structure of
the Si/SiO interface and leakage current is theoretically studied by
first-principles calculation. I found that the leakage current through the
interface with dangling bonds is 530 times larger than that without any
defects, which is expected to lead to dielectric breakdown. The direction of
the dangling bonds is closely related to the performance of the oxide as an
insulator. In addition, it is proved that the termination of the dangling bonds
by hydrogen atoms is effective for reducing the leakage current.Comment: 11 pages. to be published in Phys. Rev.
Physical transformations between quantum states
Given two sets of quantum states {A_1, ..., A_k} and {B_1, ..., B_k},
represented as sets of density matrices, necessary and sufficient conditions
are obtained for the existence of a physical transformation T, represented as a
trace-preserving completely positive map, such that T(A_i) = B_i for i = 1,
..., k. General completely positive maps without the trace-preserving
requirement, and unital completely positive maps transforming the states are
also considered
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
Spintronics for electrical measurement of light polarization
The helicity of a circularly polarized light beam may be determined by the
spin direction of photo-excited electrons in a III-V semiconductor. We present
a theoretical demonstration how the direction of the ensuing electron spin
polarization may be determined by electrical means of two
ferromagnet/semiconductor Schottky barriers. The proposed scheme allows for
time-resolved detection of spin accumulation in small structures and may have a
device application.Comment: Revised version, 8 two-column pages, 5 figures; Added: a
comprehensive time dependent analysis, figures 3b-3c & 5, equations 6 & 13-16
and 3 references. submitted to Phys. Rev.
Diffusion-emission theory of photon enhanced thermionic emission solar energy harvesters
Numerical and semi-analytical models are presented for
photon-enhanced-thermionic-emission (PETE) devices. The models take diffusion
of electrons, inhomogeneous photogeneration, and bulk and surface recombination
into account. The efficiencies of PETE devices with silicon cathodes are
calculated. Our model predicts significantly different electron affinity and
temperature dependence for the device than the earlier model based on a
rate-equation description of the cathode. We show that surface recombination
can reduce the efficiency below 10% at the cathode temperature of 800 K and the
concentration of 1000 suns, but operating the device at high injection levels
can increase the efficiency to 15%.Comment: 5 pages, 4 figure
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
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