scholarly journals Nucleation and dynamics of dislocations in mismatched heterostructures

2001 ◽  
Vol 696 ◽  
Author(s):  
Marco Patriarca ◽  
Antti Kuronen ◽  
Kimmo Kaski
Keyword(s):  
Graphical User Interface ◽  
Lattice Mismatch ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Dynamics Model ◽  
Simulation Code ◽  
System Temperature ◽  
Basic Parameters ◽  
On Line ◽  
Energy Mapping

AbstractIn this paper we have investigated, through computer simulations, dislocation nucleation and dislocation dynamics in a heterostructure system with the lattice-mismatch interface, i.e. a system with internal strain. In particular, we have studied the dependence of the nucleation thresholds on the basic parameters of the crystals, such as the amount of mismatch and the system temperature. These studies have been carried out by using the simulation code with a graphical user interface developed at our laboratory. This on-line simulation system produces a real time interactive visualization of the 3-D Molecular Dynamics model. Furthermore, it detects the presence of dislocations and tracks them by an algorithm based on potential energy mapping.

A New Dislocation-Dynamics Model and Its Application in Thin Film-Substrate Systems

2005 ◽  
Vol 875 ◽  
Author(s):  
E.H. Tan ◽  
L.Z. Sun
Keyword(s):  
Thin Films ◽  
Mechanical Performance ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Dislocation Segment ◽  
Dislocation Loops ◽  
Dynamics Model ◽  
Proposed Model ◽  
Simulation Results ◽  
Film Substrate

AbstractBased on the physical background, a new dislocation dynamics model fully incorporating the interaction among differential dislocation segments is developed to simulate 3D dislocation motion in crystals. As the numerical simulation results demonstrate, this new model completely solves the long-standing problem that simulation results are heavily dependent on dislocation-segment lengths in the classical dislocation dynamics theory. The proposed model is applied to simulate the effect of dislocations on the mechanical performance of thin films. The interactions among the dislocation loops, free surface and interfaces are rigorously computed by a decomposition method. This framework can be used to simulate how a surface loop evolves into two threading dislocations and to determine the critical thickness of thin films. Furthermore, the relationship between the film thickness and yield strength is established and compared with the conventional Hall-Petch relation.

Implementation of the ALEPH detector simulation code using UNIX with on-line graphics display

1989 ◽  
Vol 57 (1-3) ◽  
pp. 260-262 ◽  
Author(s):  
M.J. Corden ◽  
C.H. Georgiopoulos ◽  
M.E. Mermikides ◽  
J. Streets
Keyword(s):  
Simulation Code ◽  
Aleph Detector ◽  
On Line ◽  
Detector Simulation

scholarly journals Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

2016 ◽  
Vol 113 (43) ◽  
pp. 12082-12087 ◽  
Author(s):  
Ya Gai ◽  
Chia Min Leong ◽  
Wei Cai ◽  
Sindy K. Y. Tang
Keyword(s):  
Solid Mechanics ◽  
Microfluidic Channel ◽  
Deformation Mode ◽  
Dislocation Nucleation ◽  
Point Of View ◽  
Droplet Microfluidics ◽  
Dislocation Dynamics ◽  
Periodic Patterns ◽  
And Migration ◽  
Tapered Channel

When a many-body system is driven away from equilibrium, order can spontaneously emerge in places where disorder might be expected. Here we report an unexpected order in the flow of a concentrated emulsion in a tapered microfluidic channel. The velocity profiles of individual drops in the emulsion show periodic patterns in both space and time. Such periodic patterns appear surprising from both a fluid and a solid mechanics point of view. In particular, when the emulsion is considered as a soft crystal under extrusion, a disordered scenario might be expected based on the stochastic nature of dislocation dynamics in microscopic crystals. However, an orchestrated sequence of dislocation nucleation and migration is observed to give rise to a highly ordered deformation mode. This discovery suggests that nanocrystals can be made to deform more controllably than previously thought. It can also lead to novel flow control and mixing strategies in droplet microfluidics.

scholarly journals On-line Identification of Furnace Parameters for Coal-Fired Boiler Control

1999 ◽  
Vol 11 (5) ◽  
pp. 374-379 ◽  
Author(s):  
Yukio Fukayama ◽  
◽  
Kotaro Hirasawa ◽  
Katsumi Shimohira ◽  
Toshikazu Tsumura ◽  
...  
Keyword(s):  
Continuous Time ◽  
Numerical Stability ◽  
Mass Conservation ◽  
Dynamics Model ◽  
Extended Kalman Filtering ◽  
Power Station ◽  
Fuel Flow ◽  
Line Identification ◽  
Heating Surfaces ◽  
On Line

A new identifier for furnace parameters on control coalfired boilers fuel ratio dominating coal burning speed and slagging factor influencing the heat resistance on heating surfaces was applied to a 1000MWe power station. The identifier is based on the Extended Kalman Filtering on a nonlinear boiler dynamics model including energy and mass conservation laws in continuous time with seeking parameters fluctuated as the Brownian motion. The identifier refers to not only measured gas and water temperature at boilers (observable) but also actual fuel flow of each burner (manipulation) for the guidance to plant operators to cope with parameter fluctuation. Due to numerical stability, the identifier uses both Pade (1,1) approximation for time discretizing and U-D factorization for calculating the covariance matrix.

Engineering Dislocation Dynamics in Inx(AlyGa1−y)1−xP Graded Buffers Grown on Gap by Movpe

1998 ◽  
Vol 510 ◽  
Author(s):  
A.Y. Kim ◽  
E.A. Fitzgerald
Keyword(s):  
Surface Roughness ◽  
Dislocation Density ◽  
Growth Conditions ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Threading Dislocation ◽  
High Quality ◽  
Movpe Growth ◽  
Threading Dislocation Density ◽  
Buffer Design

AbstractTo engineer high-quality Inx(AlyGa1−y)1−x P/Ga1−xP graded buffers, we have explored the effects of graded buffer design and MOVPE growth conditions on material quality. We demonstrate that surface roughness causes threading dislocation density (TDD) to increase with continued grading: dislocations and roughness interact in a recursive, escalating cycle to form pileups that cause increasing roughness and dislocation nucleation. Experiments show that V/III ratio, temperature, and grading rate can be used to control dislocation dynamics and surface roughness in InxGa1−xP graded buffers. Control of these parameters individually has resulted in x = 0.34 graded buffers with TDD = 5 × 106 cm−2and roughness = 15 nm and a simple optimization has resulted in TDD = 3 × 106 cm −2and roughness = 10 un. Our most recent work has focused on more sophisticated optimization and the incorporation of aluminum for x > 0.20 to keep the graded buffer completely transparent above 545 nm. Given our results, we expect to achieve transparent, device-quality Inx(AlyGa1−y)1−x P/GaP graded buffers with TDD < 106 cm−2

Modeling of Dislocations in an Epitaxial Island Structure

2001 ◽  
Vol 673 ◽  
Author(s):  
X. H. Liu ◽  
F. M. Ross ◽  
K. W. Schwarz
Keyword(s):  
Dislocation Loop ◽  
Lattice Mismatch ◽  
Growth Behavior ◽  
Dislocation Dynamics ◽  
Stress Fields ◽  
Island Structure ◽  
Modeling Techniques ◽  
Multi Level ◽  
Good Agreement

ABSTRACTWe present calculations of dislocations in CoSi2 islands grown by reactive epitaxy on a Si(111) substrate. The stress fields due to the lattice mismatch are calculated with standard FEM techniques, and are converted into a structured, multi-level and multi-grid stress table that is imported into the PARANOID code to study the dislocation dynamics. Single and multiple dislocations in the island have been simulated, and the predicted patterns are strikingly similar to those observed experimentally. By looking at the growth behavior of very small loops we also find that dislocation-loop nucleation becomes easier as the islands become larger, and that thick islands are dislocated at smaller sizes than thin ones. These results are also in good agreement with experimental observations. We conclude that current modeling techniques are sufficient to treat this type of problem at a useful level of accuracy.

A Cluster Dynamics Model For Accumulation Of Helium In Tungsten Under Helium Ions And Neutron Irradiation

2012 ◽  
Vol 11 (5) ◽  
pp. 1547-1568 ◽  
Author(s):  
Y. G. Li ◽  
W. H. Zhou ◽  
R. H. Ning ◽  
L. F. Huang ◽  
Z. Zeng ◽  
...  
Keyword(s):  
Diffusion Processes ◽  
Rate Theory ◽  
Dynamics Model ◽  
System Temperature ◽  
Type Size ◽  
Helium Implantation ◽  
Material Conditions ◽  
Reaction Processes ◽  
And Diffusion ◽  
Good Agreement

AbstractA cluster dynamics model based on rate theory has been developed to describe the accumulation and diffusion processes of helium in tungsten under helium implantation alone or synergistic irradiation with neutron, by involving different types of objects, adopting up-to-date parameters and complex reaction processes as well as considering the diffusion process along with depth. The calculated results under different conditions are in good agreement with experiments much well. The model describes the behavior of helium in tungsten within 2D space of defect type/size and depth on different ions incident conditions (energies and fluences) and material conditions (system temperature and existent sinks), by including the synergistic effect of helium-neutron irradiations and the influence of inherent sinks (dislocation lines and grain boundaries). The model, coded as IRadMat, would be universally applicable to the evolution of defects for ions/neutron irradiated on plasma-facing materials.

Sign in / Sign up

Export Citation Format

Share Document