Relaxation of Misfit Dislocations at Nodes

2014 ◽  
Vol 783-786 ◽  
pp. 515-520 ◽  
Author(s):  
Shuai Shao ◽  
Jian Wang ◽  
Amit Misra ◽  
Richard G. Hoagland
Keyword(s):  
Misfit Dislocation ◽  
Mechanical Stability ◽  
Experimental Studies ◽  
Atomistic Simulations ◽  
Misfit Dislocations ◽  
Formation Processes ◽  
Coherent Interface ◽  
Core Energy ◽  
Structures And Properties ◽  
Coherent Interfaces

Experimental studies proved that structures and properties of misfit dislocations and their intersections (nodes) in semi-coherent interfaces strongly affect thermal and mechanical stability of interface. Employing atomistic simulations, we reveal that misfit dislocation lines can exhibit a spiral pattern (SP) or remain straight in association with dislocation character at nodes. By analyzing nodes formation processes in terms of kinetics and energetics, we found that the variation is ascribed to the competition between core energy of misfit dislocation and interface stacking fault energy with respect to coherent interface.

Tm Analysis of Interfaces Beiween Nb and Al2O3 Precipitates

1986 ◽  
Vol 82 ◽  
Author(s):  
W. Mader
Keyword(s):  
Misfit Dislocation ◽  
Diffraction Gratings ◽  
Al Alloy ◽  
Misfit Dislocations ◽  
Dislocation Theory ◽  
Coherent Interface ◽  
Periodic Arrays ◽  
Partially Coherent ◽  
Dislocation Arrangement

ABSTRACTA Nb—Al alloy has been internally oxidized to produce A12O3precipitates. The interface between plate—like AI2O3 precipitates and the Nb matrix has been investigated by diffraction, CTEM, and HREM techniques. Periodic arrays of misfit dislocations were observed which acted as diffraction gratings for the electrons. The location of misfit dislocation cores could be determined from HREM images within an accuracy of a few lattice spacings. It can be concluded that the misfit dislocations lead to a good matching of atomic rows across the interface. The dislocation arrangement at this partially coherent interface is in accordance with theoretical expectations from dislocation theory.

Interfacial Stability and Misfit Dislocation Formation in InAs/Gaas(110) Heteroepitaxy

1997 ◽  
Vol 505 ◽  
Author(s):  
Luis A. Zepeda-Ruiz ◽  
Dimitrios Maroudas ◽  
W. Henry Weinberg
Keyword(s):  
Misfit Dislocation ◽  
Film Surface ◽  
Atomic Scale ◽  
Recent Experimental Data ◽  
Misfit Dislocations ◽  
Interfacial Stability ◽  
Coherent Interface ◽  
Gaas Buffer Layer ◽  
Critical Film Thickness ◽  
Dislocation Formation

ABSTRACTA comprehensive atomic-scale study is presented of the mechanical behavior of the InAs epitaxial film, the interfacial stability with respect to misfit dislocation formation, and the film surface morphology in InAs/GaAs(110) heteroepitaxy. If a GaAs buffer layer of ten-monolayer thickness is used in the epitaxial growth, a transition is predicted from a coherent to a semi- coherent interface consisting of a regular array of edge interfacial misfit dislocations at a critical film thickness of six monolayers. A second transition to a semicoherent interface consisting of a completely developed network of perpendicularly intersecting misfit dislocations is predicted at thicknesses greater than 150 monolayers. Our simulation results are in excellent agreement with recent experimental data.

Misfit Dislocations in the Ilmenite (FeTiO3)-Hematite (Fe2O3) System

1980 ◽  
Vol 38 ◽  
pp. 212-213 ◽  
Author(s):  
K.P.D. Lagerlöf ◽  
A.H. Heuer ◽  
T.E. Mitchell
Keyword(s):  
Misfit Dislocation ◽  
Lattice Parameters ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Space Group ◽  
Two Phases ◽  
Hematite Fe2o3

It has been reported by Lally et. al. [1] that precipitates of hematite (Fe2O3, space group R3c) in a matrix of ilmenite (FeTiO3, space group R3) are lens shaped and flattened along the [0001]-direction. The coherency across the interface is lost by the introduction of a misfit dislocation network, which minimizes the strain due to the deviation in lattice parameters between the two phases [2]. The purpose of this paper is to present a new analysis of this network.

scholarly journals Prediction of Sodium Substitution Sites in Octacalcium Phosphate: The Relationships of Ionic Pair Ratios in Reacting Solutions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 240-248
Author(s):  
Yuki Sugiura ◽  
Masanori Horie
Keyword(s):  
Dicarboxylic Acid ◽  
Experimental Studies ◽  
Ionic Species ◽  
Octacalcium Phosphate ◽  
Pair Formation ◽  
Formation Processes ◽  
Ionic Pair ◽  
Substitution Process ◽  
Sodium Substitution ◽  
Acidic Conditions

Octacalcium phosphate (OCP) is widely used in biomaterial fabrication by virtue of its unique crystal structure and low environmental loading. Although various ion and molecule substitution methods into the OCP unit lattice have been introduced, it remains unclear which factors and mechanisms dominate the substitution process. Experimental studies have indicated that Na alkali metal ions are substituted at the P3 PO4 conjugated site in acidic to weakly acidic conditions and the P5 PO4 conjugated site in neutral to weak basic conditions. Ionic species calculation methods have indicated that the pair ratios of Na and HPO42− (NaHPO4−) are small in acidic reacting solutions but large under weakly basic conditions. Consequently, the roles played by NaHPO4− and ionic pair formation processes are thought to dominate ion and molecule substitution into the OCP unit lattice. Such ionic pair formation strongly inhibits dicarboxylic acid substitution into the OCP unit lattice due to the replacement of the Ca ion, which conjugates P5 PO4 as an anchor of dicarboxylic acid.

Stars and stripes. Nanoscale misfit dislocation patterns on surfaces

2002 ◽  
Vol 74 (9) ◽  
pp. 1663-1671 ◽  
Author(s):  
Raghani Pushpa ◽  
Shobhana Narasimhan
Keyword(s):  
Surface Structure ◽  
Misfit Dislocation ◽  
Domain Walls ◽  
Chemical Potential ◽  
Model System ◽  
Misfit Dislocations ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Structure Changes ◽  
Face Centered

Close-packed metal surfaces and heteroepitaxial systems frequently display a structure consisting of regularly spaced misfit dislocations, with a network of domain walls separating face-centered cubic (fcc) and hexagonal close-packed (hcp) domains. These structures can serve as templates for growing regularly spaced arrays of nanoislands. We present a theoretical investigation of the factors controlling the size and shape of the domains, using Pt(111) as a model system. Upon varying the chemical potential, the surface structure changes from being unreconstructed to the honeycomb, wavy triangles, "bright stars", or Moiré patterns observed experimentally on Pt(111) and other systems. For the particular case of Pt(111), isotropically contracted star-like patterns are favored over uniaxially contracted stripes.

scholarly journals Modeling of structuring processes at hardening of expanding cements and concretes on their basis

2018 ◽  
Vol 196 ◽  
pp. 04035 ◽  
Author(s):  
Igor Kharchenko ◽  
Alexander Panchenko ◽  
Alexey Kharchenko ◽  
Vyacheslav Alekseev
Keyword(s):  
Theoretical Analysis ◽  
Rheological Model ◽  
Experimental Studies ◽  
High Strength ◽  
Cementitious Materials ◽  
Cement Stone ◽  
Formation Processes ◽  
Structure And Properties ◽  
Potential Index ◽  
Kinetics Of

This paper reports the results of experimental research of the effect of strain-restriction conditions on the structure and properties of sulfoaluminate expanding cementitious materials. Theoretical analysis of the development of pattern formation processes is performed by applying the developed rheological model, illustrating features of the kinetics of structure-forming processes according to the ratio of the potential index of extension with linear, flat and volumetric limitation of deformations of the extension. The results show that rheological model adequately correlates with the results of experimental studies and can be described mathematically. Found that with the volume limitation of deformations arising when mixing crystallographic phases with high density and strength, the pore structure of the cement stone contains mainly gel pores. This is the main prerequisite for obtaining a dense, high-strength and durable structure of cement stone and concrete on its basis.

The Role of Misfit Dislocation During Epitaxial Growth

1987 ◽  
Vol 94 ◽  
Author(s):  
D. Cherns
Keyword(s):  
Misfit Dislocation ◽  
Lattice Spacing ◽  
Minimum Energy ◽  
Energy Criterion ◽  
Misfit Dislocations ◽  
Metal Metal ◽  
Correct Account ◽  
Pseudomorphic Growth ◽  
Dislocation Sources

ABSTRACTThe theory of Frank and van der Merwe (FM) in 1949 showed that a minimum energy criterion could explain the pseudomorphic growth of a deposit on a substrate of different lattice spacing and the subsequent relief of strain by misfit dislocations as the deposit thickness increases. Although the “equilibrium” theory is qualitatively correct, account must be taken of actual dislocation sources, which may be complex, and which may be more or less efficient for misfit relief than predicted by the FM model. Moreover, misfit dislocation sources may determine the morphology of the growing film, the interface topology and even the atomic structure of the deposit/substrate interface. These various roles of misfit dislocations are reviewed here with examples from work on metal/metal, semiconductor/semiconductor and metal/semiconductor systems.

3C-SiC Buffer Layers Converted from Si at a Low Temperature

1999 ◽  
Vol 572 ◽  
Author(s):  
H. M. Liaw ◽  
S. Q. Hong ◽  
P. Fejes ◽  
D. Werho ◽  
H. Tompkins ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Single Crystal ◽  
Misfit Dislocation ◽  
Surface Region ◽  
Buffer Layers ◽  
Misfit Dislocations ◽  
Lattice Strains ◽  
High Resolution Tem ◽  
Sic Films

ABSTRACTWe have obtained single-crystal 3C-SiC films via conversion of the surface region of Si (111) and (100) wafers at 970 °C by reaction with C2H4 in an MBE reactor. The major defects in the films were clusters, voids, and misfit dislocations. Investigation by high resolution TEM images showed low lattice strains in the epitaxial layer due to the formation of 1 misfit dislocation for every 4 to 5 regular SiC planes that are bonded to Si at the interface. The clusters and voids often occurred in pairs. A model for forming the void-cluster pairs is suggested.

Rapid Thermal Processing of Buried Sil−xGex Strained Layers; Photoluminescence Decay and Misfit Dislocation Generation.

1990 ◽  
Vol 198 ◽  
Author(s):  
D.C. Houghton ◽  
N.L. Rowell
Keyword(s):  
Quantum Wells ◽  
Misfit Dislocation ◽  
Thermal Processing ◽  
Internal Quantum Efficiency ◽  
Dislocation Nucleation ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Dislocation Generation ◽  
Strained Layers ◽  
Wide Range

ABSTRACTThe thermal constraints for device processing imposed by strain relaxation have been determined for a wide range of Si-Ge strained heterostructures. Misfit dislocation densities and glide velocities in uncapped Sil-xGex alloy layers, Sil-xGex single and multiple quantum wells have been measured using defect etching and TEM for a range of anneal temperatures (450°C-1000°C) and anneal times (5s-2000s). The decay of an intense photoluminescence peak (∼ 10% internal quantum efficiency ) from buried Si1-xGex strained layers has been correlated with the generation of misfit dislocations in adjacent Sil-xGex /Si interfaces. The misfit dislocation nucleation rate and glide velocity for all geometries and alloy compositions (0<x<0.25) were found to be thermally activated processes with activation energies of (2.5±0.2)eV and (2.3-0.65x)eV, respectively. The time-temperature regime available for thermal processing is mapped out as a function of dislocation density using a new kinetic model.

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