|
|
|
|
|
 |
|
|
Privacy &
Legal Notice |
| |
| |
|
| | |
A nanoscale bridge-type resonator is simulated using concurrent multiscale
modeling techniques. The resonator consists of a bar of semiconductor
that has been etched free from the substrate so that it can oscillate.
For the simulation, the resonator has been divided into regions in
which atomistic physics is important and regions that are well described
by continuum mechanics. The atomistic regions are simulated with MD and the
continuum regions are simulated with finite element modeling. Each
provides the boundary conditions for the other as the run simultaneously
in the simulation.
|
| | |
Concurrent Multiscale Modeling of Nanoscale MEMS
Robert E. Rudd and Byeongchan Lee
Methods: Molecular Dynamics,
Multiscale Simulation
|
| | |
The miniaturization of mechanical devices is the primary
theme in the development of Micro-Electro-Mechanical Systems
(MEMS). The qualitatively new possibilities afforded by these
systems arise because of the precision of microscopic components,
the economy of scale in semiconductor fabrication, and the
emergence of new phenomena in the scaling to small sizes.
The vast majority of MEMS mechanical devices operate at
engineering scales of microns and larger, but a new class
of MEMS devices are being developed at the nanoscale.
Fundamental challenges to MEMS design arise for these
ultrasmall devices, because the conventional rules for
device engineering based on continuum mechanics are
violated by the atomic nature of materials: the
atomic-level discreteness of matter affects the behavior
of ultrasmall MEMS.
|
| | |
This work is a theoretical study of
atomistic phenomena in the context of silicon
MEMS micro-resonators. The challenge of modeling these
devices is compounded by the fact that the atomic-scale
effects cannot be separated cleanly from larger-scale
phenomena, and the system exhibits strongly-coupled
multiscale behavior, governed
by the interplay between physics at the Angstrom, nanometer and
micron scales.
A direct, atomistic simulation of the billions of atoms
involved is prohibitive, and it would be inefficient.
Instead,
we have developed a new concurrent multiscale methodology,
which uses finite elements to model processes in the substrate
and atomistics to model processes in the smallest features of
the device. The two are run concurrently to attain a self-consistent
model of the entire system.
|
| | |
In this work we have conducted simulations of the vibrational behavior of
micron-scale oscillators. We find anomalous surface effects that are due to
atomistic processes. They show up in temperature-dependent shifts of the
resonant frequency,
degradation of the quality factor (increased dissipation) and extreme
compliance. These results are contrasted with the predictions of
continuum elastic theory as a function of size, and the failure of the
continuum techniques is clear in the limit of nanoscale MEMS.
|
| | |
SELECTED PUBLICATIONS
|
| | |
- R.E. Rudd,
"Coarse-grained molecular dynamics for computer modeling of nanomechanical systems,"
Intl. J. on Multiscale Comput. Engin. 2, 203-220 (2004).
- R.E. Rudd and J.Q. Broughton,
"Concurrent Coupling of Length Scales in Solid State Systems,"
Phys. Stat. Sol. (b) 217, 251 (2000).
- R.E. Rudd and J.Q. Broughton,
"Coarse-grained molecular dynamics and the atomic limit of finite elements,"
Phys. Rev. B 58, R5893 (1998).
- R.E. Rudd and J.Q. Broughton,
"Atomistic Simulation of MEMS Resonators through the Coupling of Length Scales,"
J. Modeling and Simulation of Microsystems 1, 29 (1999).
|
| | | |
| | |
Metals & Alloys
| Condensed Matter Physics
| Physics & Adv. Tech.
| LLNL
|
| | |
Maintained by Robert E. Rudd -- Last updated on 27 March 2006.
UCRL-WEB-229431
|