4,463 research outputs found
Nanowire Volatile RAM as an Alternative to SRAM
Maintaining benefits of CMOS technology scaling is becoming challenging due
to increased manufacturing complexities and unwanted passive power
dissipations. This is particularly challenging in SRAM, where manufacturing
precision and leakage power control are critical issues. To alleviate some of
these challenges a novel non-volatile memory alternative to SRAM was proposed
called nanowire volatile RAM (NWRAM). Due to NWRAMs regular grid based layout
and innovative circuit style, manufacturing complexity is reduced and at the
same time considerable benefits are attained in terms of performance and
leakage power reduction. In this paper, we elaborate more on NWRAM circuit
aspects and manufacturability, and quantify benefits at 16nm technology node
through simulation against state-of-the-art 6T-SRAM and gridded 8T-SRAM
designs. Our results show the 10T-NWRAM to be 2x faster and 35x better in terms
of leakage when compared to high performance gridded 8T-SRAM design
Plasmonic modulator optimized by patterning of active layer and tuning permittivity
We study an ultra-compact plasmonic modulator that can be applied in photonic
integrated circuits. The modulator is a metal-insulator-metal waveguide with an
additional ultra-thin layer of indium tin oxide (ITO). Bias is applied to the
multilayer core by means of metal plates that serve as electrodes. External
field changes carrier density in the ultra-thin ITO layer, which influences the
permittivity. The metal-insulator-metal system possesses a plasmon resonance,
and it is strongly affected by changes in the permittivity of the active layer.
To improve performance of the structure we propose several optimizations. We
examine influence of the ITO permittivity on the modulator's performance and
point out appropriate values. We analyze eigenmodes of the waveguide structure
and specify the range for its efficient operation. We show that substituting
the continuous active layer by a one-dimension periodic stripes increases
transmittance through the device and keeps the modulator's performance at the
same level. The dependence on the pattern size and filling factor of the active
material is analyzed and optimum parameters are found. Patterned ITO layers
allow us to design a Bragg grating inside the waveguide. The grating can be
turned on and off, thus modulating reflection from the structure. The
considered structure with electrical control possesses a high performance and
can efficiently work as a plasmonic component in nanophotonic architectures.Comment: Optics Communications (2012
Diameter-Selective Dispersion of Carbon Nanotubes via Polymers: A Competition between Adsorption and Bundling
The mechanism of the selective dispersion of single-walled carbon nanotubes
(CNTs) by polyfluorene polymers is studied in this paper. Using extensive
molecular dynamics simulations, it is demonstrated that diameter selectivity is
the result of a competition between bundling of CNTs and adsorption of polymers
on CNT surfaces. The preference for certain diameters corresponds to local
minima of the binding energy difference between these two processes. Such
minima in the diameter dependence occur due to abrupt changes in the CNT's
coverage with polymers and their calculated positions are in quantitative
agreement with preferred diameters, reported experimentally. The presented
approach defines a theoretical framework for the further understanding and
improvement of dispersion/extraction processes.Comment: 22 pages, 5 figures, ACS Nano (2015
Efficient, designable, and broad-bandwidth optical extinction via aspect-ratio-tailored silver nanodisks
Subwavelength resonators, ranging from single atoms to metallic
nanoparticles, typically exhibit a narrow-bandwidth response to optical
excitations. We computationally design and experimentally synthesize tailored
distributions of silver nanodisks to extinguish light over broad and varied
frequency windows. We show that metallic nanodisks are two-to-ten-times more
efficient in absorbing and scattering light than common structures, and can
approach fundamental limits to broadband scattering for subwavelength
particles. We measure broadband extinction per volume that closely approaches
theoretical predictions over three representative visible-range wavelength
windows, confirming the high efficiency of nanodisks and demonstrating the
collective power of computational design and experimental precision for
developing new photonics technologies
Low Voltage Nanoelectromechanical Switches Based on Silicon Carbide Nanowires
We report experimental demonstrations of electrostatically actuated, contact-mode nanoelectromechanical switches based on very thin silicon carbide (SiC) nanowires (NWs). These NWs are lithographically patterned from a 50 nm thick SiC layer heteroepitaxially grown on single-crystal silicon (Si). Several generic designs of in-plane electrostatic SiC NW switches have been realized, with NW widths as small as ~20 nm and lateral switching gaps as narrow as ~10 nm. Very low switch-on voltages are obtained, from a few volts down to ~1 V level. Two-terminal, contact-mode “hot” switching with high on/off ratios (>10^2 or 10^3) has been demonstrated repeatedly for many devices. We find enhanced switching performance in bare SiC NWs, with lifetimes exceeding those based on metallized SiC NWs
Towards improved exact exchange functionals relying on GW quasiparticle methods for parametrization
We use fully self-consistent GW calculations on diamond and silicon carbide
to reparametrize the Heyd-Scuseria-Ernzerhof exact exchange density functional
for use in band structure calculations of semiconductors and insulators. We
show that the thus modified functional is able to calculate the band structure
of bulk Si, Ge, GaAs, and CdTe with good quantitative accuracy at a
significantly reduced computational cost as compared to GW methods. We discuss
the limitations of this functional in low-dimensions by calculating the band
structures of single-layer hexagonal BN and MoS, and by demonstrating
that the diameter scaling of curvature induced band gaps in single-walled
carbon nanotubes is still physically incorrect using our functional; we
consider possible remedies to this problem.Comment: Submitted to Physical Review
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