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Nonequilibrium Interface and Surface Dynamics 2007
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A Level-Set Method for Self-Organized Pattern
Formation during heteroepitaxial growth
CSIC Building (#406),
Seminar Room 4122.
Directions: home.cscamm.umd.edu/directions
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A Level-Set Method for Self-Organized Pattern
Formation during heteroepitaxial growth
Professor
Christian Ratsch
UCLA
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Abstract:
We have developed an island dynamics model for
heteroepitaxial growth that employs an island
dynamics model with the level-set technique in
combination with a fully self-consistent elastic
model. At every timestep in the simulation, we solve
the elastic equations for the entire system. This is
possible within our approach because the numerical
timestep can be chosen much larger than in an
atomistic simulation. At every lattice site strain
then changes the local bonding, and thus the
potential energy surface for adatoms and the
microscopic parameters of the simulation. In
particular, strain changes the diffusivity of
adatoms and enhances the rate of detachment from
island edges. We show that the island size
distribution becomes more regular when strain
increases. The reason is that bigger islands are
typically more strained than smaller islands, and
thus their growth is slowed down. We also present
results that show how strain induced by buried
islands influences the nucleation of new islands in
higher layers, and in fact leads to a regularization
of stacked islands or quantum dots. Our results
indicate that for stacked quantum dots that are
separated by a buffer layer, there exists an optimal
thickness of the buffer layer for best
regularization of the stacked dots. |
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