排序方式: 共有47条查询结果,搜索用时 15 毫秒
1.
2.
We have developed an accurate Padé approximant for the plasma dispersion function that is valid for degenerate semiconductors
that occur in ultra-small MOSFETs. The new approximant is based on a two pole model that enables a simple evaluation of the
Lindhard dielectric function for the full dynamic response of electrons of any degeneracy. The importance of this result is
that it enables a fast numerical algorithm for determining the energies and scattering strengths of coupled plasmon-phonon
modes in silicon MOSFET devices with high-κ gate stacks. Moreover, the formalism allows the systematic inclusion of Landau
damping and other processes such as collisional damping that damp out some of the modes at particular ranges of wave vector.
The new model is a non-trivially scaled model of a previous approximant derived for Boltzmann statistics. The new model reduces
to the classical result in the appropriate limit. Results are presented that compare the exact numerically computed complex
plasma dispersion function with the new Padé approximant model. Comparison is also made between exact numerical calculations
and the Padé approximant model for static screening. A brief outline is made of the potential application to high-κ gate stack
devices where the formalism should provide a significantly large reduction in complexity that will enable efficient Monte
Carlo simulation of SO phonon and plasmon scattering. 相似文献
3.
4.
A. Asenov J.R. Watling A.R. Brown D.K. Ferry 《Journal of Computational Electronics》2002,1(4):503-513
As MOSFETs are scaled to sub 100 nm dimensions, quantum mechanical confinement in the direction normal to the silicon dioxide interface and tunnelling (through the gate oxide, band-to-band and from source-to-drain) start to strongly affect their characteristics. Recently it has been demonstrated that first order quantum corrections can be successfully introduced in self-consistent drift diffusion-type models using Quantum Potentials. In this paper we describe the introduction of such quantum corrections within a full 3D drift diffusion simulation framework. We compare the two most popular quantum potential techniques: density gradient and the effective potential approaches, in terms of their justification, accuracy and computational efficiency. The usefulness of their 3D implementation is demonstrated with examples of statistical simulations of intrinsic fluctuation effects in decanano MOSFETs introduced by discrete random dopants. We also discuss the capability of the density gradient formalism to handle direct source-to-drain tunnelling in sub 10 nm double-gate MOSFETS, illustrated in comparison with Non-Equilibrium Green's Functions simulations. 相似文献
5.
Fitsum Teklu Agachai Sumalee David Watling 《Computer-Aided Civil and Infrastructure Engineering》2007,22(1):31-43
Abstract: It is well known that coordinated, area-wide traffic signal control provides great potential for improvements in delays, safety, and environmental measures. However, an aspect of this problem that is commonly neglected in practice is the potentially confounding effect of drivers re-routing in response to changes in travel times on competing routes, brought about by the changes to the signal timings. This article considers the problem of optimizing signal green and cycle timings over an urban network, in such a way that the optimization anticipates the impact on traffic routing patterns. This is achieved by including a network equilibrium model as a constraint to the optimization. A Genetic Algorithm (GA) is devised for solving the resulting problem, using total travel time across the network as an illustrative fitness function, and with a widely used traffic simulation-assignment model providing the equilibrium flows. The procedure is applied to a case study of the city of Chester in the UK, and the performance of the algorithms is analyzed with respect to the parameters of the GA method. The results show a better performance of the signal timing as optimized by the GA method as compared to a method that does not consider rerouting. This improvement is found to be more significant with a more congested network whereas under a relatively mild congestion situation the improvement is not very clear. 相似文献
6.
7.
8.
Polarization studies have been carried out to determine the influence of diisobutyldithiophosphinate (DIBDTPI) on the dissolution of silver in cyanide solutions at pH 11. DIBDTPI was found to inhibit dissolution at concentrations similar to those used when this compound is applied as a flotation collector. The inhibition efficiency in 10–2 mol dm–3 CN– was found to increase with increase in DIBDTPI concentration in the range 10–6–10–4 mol dm–3, and with increase in time of exposure of the silver to the DIBDTPI solution. The inhibition efficiency found for 10–4 mol dm–3 DIBDTPI in quiescent 10–2 mol dm–3 CN– solution at 23 °C was 64.6% and 95.0% for exposure times of 10 min and 2 h, respectively. These values are significantly less than those found previously for 2-mercaptobenzothiazole under the same conditions. Surface enhanced Raman spectroscopy showed that inhibition was associated with adsorption of DIBDTPI displacing cyanide from the silver surface. Voltammetry at 0.5 mV s–1 indicated that adsorption of DIBDTPI involves charge transfer. 相似文献
9.
10.
The rates and product selectivities of the C3H6-NO-O2 and NO-H2 reactions over a Pt/Al2O3 catalyst, and of the straight, NO decomposition reaction over the reduced catalyst have been compared at 240C. The rate of NO decomposition over the reduced catalyst is seven times greater than the rate of NO decomposition in the C3H6-NO-O2 reaction. This is consistent with a mechanism in which NO decomposition occurs on Pt sites reduced by the hydrocarbon, provided only that at steady state in the lean NO
x
reaction about 14% of the Pt sites are in the reduced form. However, the (extrapolated) rate of the NO-H2 reaction at 240C is about 104 times faster than the rate of the NO decomposition reaction thus raising the possibility that NO decomposition in the former reaction is assisted by Hads. It is suggested that adsorbate-assisted NO decomposition in the C3H6-NO-O2 reaction could be very important. This would mean that the proportion of reduced Pt sites required in the steady state would be extremely small. The NO decomposition and the NO-H2 reactions produce no N2O, unlike the C3H6-NO-O2 reaction, suggesting that adsorbed NO is completely dissociated in the first two cases, but only partially dissociated in the latter case. It is possible that some of the associatively adsorbed NO present during the C3H6-NO-O2 reaction may be adsorbed on oxidised Pt sites. 相似文献