54,650 research outputs found
Universal characteristics of resonant-tunneling field emission from nanostructured surfaces
We have performed theoretical and experimental studies of field emission from
nanostructured semiconductor cathodes. Resonant tunneling through
electric-field-induced interface bound states is found to strongly affect the
field-emission characteristics. Our analytical theory predicts power-law and
Lorentzian-shaped current-voltage curves for resonant-tunneling field emission
from three-dimensional substrates and two-dimensional accumulation layers,
respectively. These predicted line shapes are observed in field emission
characteristics from self-assembled silicon nanostructures. A simple model
describes formation of an accumulation layer and of the resonant level in these
systems.Comment: 5 pages, 4 figures, RevTex, to appear in J. Appl. Phy
Coral symbiodinium community composition across the Belize Mesoamerican barrier reef system is influenced by host species and thermal variability
Accepted manuscrip
Precision Charmonium Spectroscopy From Lattice QCD
We present results for Charmonium spectroscopy using Non-Relativistic QCD
(NRQCD). For the NRQCD action the leading order spin-dependent and next to
leading order spin-independent interactions have been included with
tadpole-improved coefficients. We use multi-exponential fits to multiple
correlation functions to extract ground and excited states. Splittings
between the lowest , and states are given and we have accurate
values for the state hyperfine splitting and the fine structure.
Agreement with experiment is good - the remaining systematic errors are
discussed.Comment: 23 pages uuencoded latex file. Contains figures in late
Hierarchical approach to 'atomistic' 3-D MOSFET simulation
We present a hierarchical approach to the 'atomistic' simulation of aggressively scaled sub-0.1-μm MOSFETs. These devices are so small that their characteristics depend on the precise location of dopant atoms within them, not just on their average density. A full-scale three-dimensional drift-diffusion atomistic simulation approach is first described and used to verify more economical, but restricted, options. To reduce processor time and memory requirements at high drain voltage, we have developed a self-consistent option based on a solution of the current continuity equation restricted to a thin slab of the channel. This is coupled to the solution of the Poisson equation in the whole simulation domain in the Gummel iteration cycles. The accuracy of this approach is investigated in comparison to the full self-consistent solution. At low drain voltage, a single solution of the nonlinear Poisson equation is sufficient to extract the current with satisfactory accuracy. In this case, the current is calculated by solving the current continuity equation in a drift approximation only, also in a thin slab containing the MOSFET channel. The regions of applicability for the different components of this hierarchical approach are illustrated in example simulations covering the random dopant-induced threshold voltage fluctuations, threshold voltage lowering, threshold voltage asymmetry, and drain current fluctuations
Study of the Barringer Refractor Plate Correlation Spectrometer as a remote sensing instrument
Barringer refractor plate correlation spectrometer as remote sensing instrument of pollutant gases in atmospher
Electronic and optical properties of quantum wells embedded in wrinkled nanomembranes
The authors theoretically investigate quantum confinement and transition
energies in quantum wells (QWs) asymmetrically positioned in wrinkled
nanomembranes. Calculations reveal that the wrinkle profile induces both blue-
and redshifts depending on the lateral position of the QW probed. Relevant
radiative transistions include the ground state of the electron (hole) and
excited states of the hole (electron). Energy shifts as well as stretchability
of the structure are studied as a function of wrinkle amplitude and period.
Large tunable bandwidths of up to 70 nm are predicted for highly asymmetric
wrinkled QWs.Comment: 3 pages, 4 figures. The following article has been submitted to
Applied Physics Letters. After it is published, it will be found at
http://apl.aip.or
The Heavy-Light Spectrum from Lattice NRQCD
We present a lattice investigation of heavy-light mesons in the quenched
approximation, using non-relativistic QCD for the heavy quark and a clover
improved Wilson formulation for the light quark. A comprehensive calculation of
the heavy-light spectrum has been performed for various heavy quark masses
around the . Our results for the splitting agree well with the
experimental value. We find the splitting to be compatible with
experiment, albeit with large error bars. Our splitting is slightly
low, which could be explained as an effect of quenching. For the first time, we
are able to estimate the mass of states at the and compare them with
experiment.Comment: 24 pages, latex, 10 figures in uuencoded compressed postscrip
Possible origin of the 0.5 plateau in the ballistic conductance of quantum point contacts
A non-equilibrium Green function formalism (NEGF) is used to study the
conductance of a side-gated quantum point contact (QPC) in the presence of
lateral spin-orbit coupling (LSOC). A small difference of bias voltage between
the two side gates (SGs) leads to an inversion asymmetry in the LSOC between
the opposite edges of the channel. In single electron modeling of transport,
this triggers a spontaneous but insignificant spin polarization in the QPC.
However, the spin polarization of the QPC is enhanced substantially when the
effect of electron-electron interaction is included. The spin polarization is
strong enough to result in the occurrence of a conductance plateau at 0.5G0 (G0
= 2e2/h) in the absence of any external magnetic field. In our simulations of a
model QPC device, the 0.5 plateau is found to be quite robust and survives up
to a temperature of 40K. The spontaneous spin polarization and the resulting
magnetization of the QPC can be reversed by flipping the polarity of the source
to drain bias or the potential difference between the two SGs. These numerical
simulations are in good agreement with recent experimental results for
side-gated QPCs made from the low band gap semiconductor InAs
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