Plasticity in Polycrystalline Thin Films: a 2D Dislocation Dynamics Approach

2003 ◽  
Vol 779 ◽  
Author(s):  
Lucia Nicola ◽  
Erik Van der Giessen ◽  
Alan Needleman
Keyword(s):  
Thin Films ◽  
Dislocation Dynamics ◽  
Stress Evolution ◽  
Polycrystalline Thin Films ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Strain Formulation ◽  
The Difference ◽  
Film Substrate ◽  
Edge Dislocations

AbstractThermal stress evolution in polycrystalline thin films is analyzed using discrete dislocation plasticity. Stress develops in the film during cooling from a stress-free configuration due to the difference in thermal expansion coefficient between the film and its substrate. A plane strain formulation with only edge dislocations is used and each grain of the polycrystal has a specified set of slip systems. The film–substrate interface and the grain boundaries are impenetrable for the dislocations. Results are presented for two film thicknesses, with higher hardening seen for the thinner films.

scholarly journals Relaxation of Thermal Stress by Dislocation Motion in Passivated Metal Interconnects

2004 ◽  
Vol 19 (4) ◽  
pp. 1216-1226 ◽  
Author(s):  
Lucia Nicola ◽  
Erik Van der Giessen ◽  
Alan Needleman
Keyword(s):  
Dislocation Motion ◽  
Slip Systems ◽  
Stress Evolution ◽  
Discrete Dislocation ◽  
Passivation Layers ◽  
Strain Formulation ◽  
On Line ◽  
Pitch Length ◽  
Metal Interconnects ◽  
Edge Dislocations

The development and relaxation of stress in metal interconnects strained by their surroundings (substrate and passivation layers) is predicted by a discrete dislocation analysis. The model is based on a two-dimensional plane strain formulation, with deformation fully constrained in the line direction. Plastic deformation occurs by glide of edge dislocations on three slip systems in the single-crystal line. The substrate and passivation layers are treated as elastic materials and therefore impenetrable for the dislocations. Results of the simulations show the dependence of the stress evolution and of the effectiveness of plastic relaxation on the geometry of the line. The dependence of stress development on line aspect ratio, line size, slip plane orientation, pitch length, and passivation layer thickness are explored.

scholarly journals Size effects in polycrystalline thin films analyzed by discrete dislocation plasticity

2005 ◽  
Vol 479 (1-2) ◽  
pp. 329-338 ◽  
Author(s):  
Lucia Nicola ◽  
Erik Van der Giessen ◽  
Alan Needleman
Keyword(s):  
Thin Films ◽  
Size Effects ◽  
Polycrystalline Thin Films ◽  
Discrete Dislocation ◽  
Dislocation Plasticity

Simulations of Dislocation Dynamics in Aluminum Interconnects

2002 ◽  
Vol 731 ◽  
Author(s):  
Lucia Nicola ◽  
Erik Van der Giessen ◽  
Alan Needleman
Keyword(s):  
Thermal Stress ◽  
Cross Section ◽  
Dislocation Dynamics ◽  
Local Concentration ◽  
Small Cross Section ◽  
Discrete Dislocation ◽  
Thermal Stress Field ◽  
Strain Formulation ◽  
Edge Dislocations ◽  
Aluminum Interconnects

AbstractA discrete dislocation simulation of plastic deformation in metallic interconnects caused by thermal stress is carried out. The calculations are carried out using a two dimensional plane strain formulation with only edge dislocations. A boundary value problem is formulated and solved for the evolution of the thermal stress field and the evolution of the dislocation structure in the cross-section of the line as cooling proceeds. For lines with a small cross section (height or width less than 1 μm), the local concentration of stresses due to dislocation patterning strongly affects the overall stress build up and relaxation. The results show a clear dependence of the transverse stress development on the line aspect ratio.

Cyclic Bending Response of Single- and Polycrystalline Thin Films: Two Dimensional Discrete Dislocation Dynamics

2013 ◽  
Vol 275-277 ◽  
pp. 132-137 ◽  
Author(s):  
Hai Dong Fan ◽  
Qing Yuan Wang ◽  
Muhammad Kashif Khan
Keyword(s):  
Thin Films ◽  
Interaction Model ◽  
Cyclic Hardening ◽  
Dislocation Dynamics ◽  
Two Dimensional ◽  
Cyclic Bending ◽  
Discrete Dislocation Dynamics ◽  
Polycrystalline Thin Films ◽  
Discrete Dislocation ◽  
Bending Response

The bending behavior of single- and polycrystalline thin films is modeled by two-dimensional discrete dislocation dynamics (DDD) to study the cyclic bending response. In the polycrystalline films, grain boundaries (GBs) are simulated with a penetrable dislocation-GB interaction model. Our results reveal that the single- and polycrystalline thin films under pure bending exhibit strong Bauschinger effect but no cyclic hardening or softening. Furthermore, the uploading response of each cycle can be divided into three stages, which are associated with the glide, annihilation and nucleation of dislocations, respectively.

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.

Void and Dislocation Microstructure Development in Heteroepitaxial Film Growth

1995 ◽  
Vol 399 ◽  
Author(s):  
Richard W. Smith ◽  
David J. Srolovitz
Keyword(s):  
Thin Films ◽  
Molecular Dynamics ◽  
Film Growth ◽  
Lattice Misfit ◽  
Two Dimensional ◽  
Microstructure Development ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Film Substrate ◽  
Edge Dislocations

ABSTRACTTwo dimensional, non-equilibrium molecular dynamics simulations have been performed to examine the microstructures of both homoepitaxial and heteroepitaxial thin films grown on single crystal substrates. The principal microstructural features to develop within these films are small voids and edge dislocations. Voids form near the surface of the growing film as surface depressions between microcolumns pinch off to become closed volumes. These voids often form in such a way as to introduce dislocations into the crystal with their cores positioned within the voids. Dislocations are also formed during heteroepitaxy at the interface between the substrate and film. These dislocations tend to be mobile. When voids are present in the film and when the lattice misfit is low, dislocations tend to be trapped in the voids or pulled toward them due to dislocation image interactions. Once attached to voids, dislocations are effectively pinned there. When voids are absent or when the misfit is high, dislocations are restricted to the film-substrate interface. In the case of heteroepitaxy, dislocations are found to relieve either tensile or compressive misfit stresses. Misfit stresses may also be accommodated, to some extent, merely by the free volume of the voids themselves.

A Discrete Dislocation Plasticity Analysis of Plane-Strain Indentation of a Single-Crystal Half-Space by a Smooth and a Rough Rigid Asperity

2010 ◽  
Author(s):  
X. Yin ◽  
K. Komvopoulos
Keyword(s):  
Single Crystal ◽  
Plane Strain ◽  
Half Space ◽  
Crystal Surface ◽  
Normal Load ◽  
Surface Profile ◽  
Dislocation Source ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Edge Dislocations

A discrete dislocation plasticity analysis of plane-strain indentation of a single-crystal half-space by a smooth or rough (fractal) rigid asperity is presented. The emission, movement, and annihilation of edge dislocations are incorporated in the analysis through a set of constitutive rules [1,2]. It is shown that the initiation of the first dislocation is controlled by the subsurface Hertzian stress field and occurs in the ±45° direction with respect to the normal of the crystal surface, in agreement with the macroscopic yielding behavior of the indented halfspace. For fixed slip-plane direction, the dislocation density increases with the applied normal load and dislocation source density. The dislocation multiplication behavior at a given load is compared with that generated by a rough indenter with a fractal surface profile. The results of the analysis provide insight into yielding and plastic deformation phenomena in indented single-crystal materials.

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