21,245 research outputs found
Speckle noise in satellite based lidar systems
The lidar system model was described, and the statistics of the signal and noise at the receiver output were derived. Scattering media effects were discussed along with polarization and atmospheric turbulence. The major equations were summarized and evaluated for some typical parameters
Full 3D Quantum Transport Simulation of Atomistic Interface Roughness in Silicon Nanowire FETs
The influence of interface roughness scattering (IRS) on the performances of
silicon nanowire field-effect transistors (NWFETs) is numerically investigated
using a full 3D quantum transport simulator based on the atomistic sp3d5s*
tight-binding model. The interface between the silicon and the silicon dioxide
layers is generated in a real-space atomistic representation using an
experimentally derived autocovariance function (ACVF). The oxide layer is
modeled in the virtual crystal approximation (VCA) using fictitious SiO2 atoms.
-oriented nanowires with different diameters and randomly generated
surface configurations are studied. The experimentally observed ON-current and
the threshold voltage is quantitatively captured by the simulation model. The
mobility reduction due to IRS is studied through a qualitative comparison of
the simulation results with the experimental results
Modeling surface roughness scattering in metallic nanowires
Ando's model provides a rigorous quantum-mechanical framework for
electron-surface roughness scattering, based on the detailed roughness
structure. We apply this method to metallic nanowires and improve the model
introducing surface roughness distribution functions on a finite domain with
analytical expressions for the average surface roughness matrix elements. This
approach is valid for any roughness size and extends beyond the commonly used
Prange-Nee approximation. The resistivity scaling is obtained from the
self-consistent relaxation time solution of the Boltzmann transport equation
and is compared to Prange-Nee's approach and other known methods. The results
show that a substantial drop in resistivity can be obtained for certain
diameters by achieving a large momentum gap between Fermi level states with
positive and negative momentum in the transport direction.Comment: 25 pages, 11 figure
Coherent transport through graphene nanoribbons in the presence of edge disorder
We simulate electron transport through graphene nanoribbons of experimentally
realizable size (length L up to 2 micrometer, width W approximately 40 nm) in
the presence of scattering at rough edges. Our numerical approach is based on a
modular recursive Green's function technique that features sub-linear scaling
with L of the computational effort. We identify the influence of the broken A-B
sublattice (or chiral) symmetry and of K-K' scattering by Fourier spectroscopy
of individual scattering states. For long ribbons we find Anderson-localized
scattering states with a well-defined exponential decay over 10 orders of
magnitude in amplitude.Comment: 8 pages, 6 Figure
Surface roughness measuring system
Significant height information of ocean waves, or peaks of rough terrain is obtained by compressing the radar signal over different widths of the available chirp or Doppler bandwidths, and cross-correlating one of these images with each of the others. Upon plotting a fixed (e.g., zero) component of the cross-correlation values as the spacing is increased over some empirically determined range, the system is calibrated. To measure height with the system, a spacing value is selected and a cross-correlation value is determined between two intensity images at a selected frequency spacing. The measured height is the slope of the cross-correlation value used. Both electronic and optical radar signal data compressors and cross-correlations are disclosed for implementation of the system
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