2,566 research outputs found
Matrix multiplication using quantum-dot cellular automata to implement conventional microelectronics
Quantum-dot cellular automata (QCA) shows promise as a post silicon CMOS, low
power computational technology. Nevertheless, to generalize QCA for
next-generation digital devices, the ability to implement conventional
programmable circuits based on NOR, AND, and OR gates is necessary. To this
end, we devise a new QCA structure, the QCA matrix multiplier (MM), employing
the standard Coulomb blocked, five quantum dot (QD) QCA cell and
quasi-adiabatic switching for sequential data latching in the QCA cells. Our
structure can multiply two N x M matrices, using one input and one
bidirectional input/output data line. The calculation is highly parallelizable,
and it is possible to achieve reduced calculation time in exchange for
increasing numbers of parallel matrix multiplier units. We show convergent, ab
initio simulation results using the Intercellular Hartree Approximation for
one, three, and nine matrix multiplier units. The structure can generally
implement any programmable logic array (PLA) or any matrix multiplication based
operation.Comment: 14 pages, 9 figures, supplemental informatio
In Situ Thermal Decomposition of Exfoliated Two-Dimensional Black Phosphorus
With a semiconducting band gap and high charge carrier mobility,
two-dimensional (2D) black phosphorus (BP), often referred to as phosphorene,
holds significant promise for next generation electronics and optoelectronics.
However, as a 2D material, it possesses a higher surface area to volume ratio
than bulk BP, suggesting that its chemical and thermal stability will be
modified. Herein, an atomic-scale microscopic and spectroscopic study is
performed to characterize the thermal degradation of mechanically exfoliated 2D
BP. From in situ scanning/transmission electron microscopy, decomposition of 2D
BP is observed to occur at ~400 {\deg}C in vacuum, in contrast to the 550
{\deg}C bulk BP sublimation temperature. This decomposition initiates via
eye-shaped cracks along the [001] direction and then continues until only a
thin, amorphous red phosphorous like skeleton remains. In situ electron energy
loss spectroscopy, energy-dispersive X-ray spectroscopy, and energy-loss
near-edge structure changes provide quantitative insight into this chemical
transformation process.Comment: In press: 4 figures in main manuscript, 27 pages with supporting
informatio
Solvent Exfoliation of Electronic-Grade, Two-Dimensional Black Phosphorus
Solution dispersions of two-dimensional (2D) black phosphorus (BP), often
referred to as phosphorene, are achieved by solvent exfoliation. These
pristine, electronic-grade BP dispersions are produced with anhydrous, organic
solvents in a sealed tip ultrasonication system, which circumvents BP
degradation that would otherwise occur via solvated oxygen or water. Among
conventional solvents, n-methyl-pyrrolidone (NMP) is found to provide stable,
highly concentrated (~0.4 mg/mL) BP dispersions. Atomic force microscopy,
scanning electron microscopy, transmission electron microscopy, Raman
spectroscopy, and X-ray photoelectron spectroscopy show that the structure and
chemistry of solvent-exfoliated BP nanosheets are comparable to mechanically
exfoliated BP flakes. Additionally, residual NMP from the liquid-phase
processing suppresses the rate of BP oxidation in ambient conditions.
Solvent-exfoliated BP nanosheet field-effect transistors (FETs) exhibit
ambipolar behavior with current on/off ratios and mobilities up to ~10000 and
~50 cm^2/(V*s), respectively. Overall, this study shows that stable, highly
concentrated, electronic-grade 2D BP dispersions can be realized by scalable
solvent exfoliation, thereby presenting opportunities for large-area,
high-performance BP device applications.Comment: 6 figures, 31 pages, including supporting informatio
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