12,385 research outputs found
A Pearson Effective Potential for Monte-Carlo simulation of quantum confinement effects in various MOSFET architectures
A Pearson Effective Potential model for including quantization effects in the
simulation of nanoscale nMOSFETs has been developed. This model, based on a
realistic description of the function representing the non zero-size of the
electron wave packet, has been used in a Monte-Carlo simulator for bulk, single
gate SOI and double-gate SOI devices. In the case of SOI capacitors, the
electron density has been computed for a large range of effective field
(between 0.1 MV/cm and 1 MV/cm) and for various silicon film thicknesses
(between 5 nm and 20 nm). A good agreement with the Schroedinger-Poisson
results is obtained both on the total inversion charge and on the electron
density profiles. The ability of an Effective Potential approach to accurately
reproduce electrostatic quantum confinement effects is clearly demonstrated.Comment: 13 pages, 11 figures, 3 table
Fast Molecular-Dynamics Simulation for Ferroelectric Thin-Film Capacitors Using a First-Principles Effective Hamiltonian
A newly developed fast molecular-dynamics method is applied to BaTiO3
ferroelectric thin-film capacitors with short-circuited electrodes or under
applied voltage. The molecular-dynamics simulations based on a first-principles
effective Hamiltonian clarify that dead layers (or passive layers) between
ferroelectrics and electrodes markedly affect the properties of capacitors, and
predict that the system is unable to hop between a uniformly polarized
ferroelectric structure and a striped ferroelectric domain structure at low
temperatures. Simulations of hysteresis loops of thin-film capacitors are also
performed, and their dependence on film thickness, epitaxial constraints, and
electrodes are discussed.Comment: 12 figures, 1 table. Submitted to PRB v2->v3: Major changes are
underlined in the manuscript. Added new reference
Stabilizing the forming process in unipolar resistance switching using an improved compliance current limiter
The high reset current IR in unipolar resistance switching now poses major
obstacles to practical applications in memory devices. In particular, the first
IR-value after the forming process is so high that the capacitors sometimes do
not exhibit reliable unipolar resistance switching. We found that the
compliance current Icomp is a critical parameter for reducing IR-values. We
therefore introduced an improved, simple, easy to use Icomp-limiter that
stabilizes the forming process by drastically decreasing current overflow, in
order to precisely control the Icomp- and subsequent IR-values.Comment: 15 pages, 4 figure
Pade-Type Model Reduction of Second-Order and Higher-Order Linear Dynamical Systems
A standard approach to reduced-order modeling of higher-order linear
dynamical systems is to rewrite the system as an equivalent first-order system
and then employ Krylov-subspace techniques for reduced-order modeling of
first-order systems. While this approach results in reduced-order models that
are characterized as Pade-type or even true Pade approximants of the system's
transfer function, in general, these models do not preserve the form of the
original higher-order system. In this paper, we present a new approach to
reduced-order modeling of higher-order systems based on projections onto
suitably partitioned Krylov basis matrices that are obtained by applying
Krylov-subspace techniques to an equivalent first-order system. We show that
the resulting reduced-order models preserve the form of the original
higher-order system. While the resulting reduced-order models are no longer
optimal in the Pade sense, we show that they still satisfy a Pade-type
approximation property. We also introduce the notion of Hermitian higher-order
linear dynamical systems, and we establish an enhanced Pade-type approximation
property in the Hermitian case
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