Misfit Dislocations and Elastic Relaxation

1995 ◽  
Vol 399 ◽  
Author(s):  
H.P Strunk ◽  
S. Christiansen ◽  
M. Albrecht
Keyword(s):  
Driving Forces ◽  
Maximum Shear Stress ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Local Strain ◽  
Misfit Strain ◽  
Relaxation Mechanism ◽  
Misfit Dislocations ◽  
Thermodynamical Equilibrium ◽  
Three Dimensional Finite Element

ABSTRACTPrior to relaxation of misfit strain by formation of misfit dislocations, a growing heteroepitaxial layer can relax elastically by forming surface undulations called ripples. With increasing amplitude of the ripples the misfit strain and thus stress fields grow markedly inhomogeneous, and dislocation formation may thus be triggered in areas of maximum shear stress. The surface directly above such a new dislocation then represents a band of preferential growth and develops into a ridge, which in turn redistributes the strain in the growing layer. This interwoven elastic/plastic relaxation mechanism can comparably easily be deduced from transmission electron and atomic force microscopy studies of SiGe layers grown onto silicon by liquid phase epitaxy. This growth technique exerts only very small driving forces and thus operates very near thermodynamical equilibrium. The local strain tensor and strain energy density are calculated for the actual layer geometries by three dimensional finite element method and provide for quantification of the mechanism.

Transmission Electron Diffraction Techniques for Nm Scale Strain Measurement in Semiconductors

1995 ◽  
Vol 405 ◽  
Author(s):  
J. Vanhellemont ◽  
K. G. F. Janssens ◽  
S. Frabboni ◽  
P. Smeys ◽  
R. Balboni ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Three Dimensional ◽  
Local Strain ◽  
Quantitative Information ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Convergent Beam

AbstractAn overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.

The Initial Stages of MBE Growth of InSb on GaAs(100) - A High Misfit Heterointerface

1989 ◽  
Vol 159 ◽  
Author(s):  
C.J. Kiely ◽  
A. Rockett ◽  
J-I. Chyi ◽  
H. Morkoc
Keyword(s):  
Three Dimensional ◽  
Misfit Strain ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Island Growth ◽  
Mbe Growth ◽  
Edge Type ◽  
Transmission Electron ◽  
Interfacial Defects ◽  
Square Array

ABSTRACTThe initial stages of heteroepitaxy of InSb on GaAs(100) grown by MBE have been studied by transmission electron microscopy. Three dimensional InSb island growth occurs in which the majority of the 14.6% misfit strain is accommodated by a square array of a/2<011= edge-type misfit dislocations. The implications of each island having a well defined defect array before coalescence into a continuous epilayer are discussed. Some 600-type a/2<101= interfacial defects and associated threading dislocations are also observed in coalesced films and possible reasons for their existence are explained. A strong asymmetrical distribution of planar defects in the InSb islands is observed and the origin of the asymmetry is discussed. Finally some evidence for local intermixing in the vicinity of the interface is presented.

scholarly journals Reorientation of Misfit Dislocations During Annealing in InGaAs/GaAs(001) Interfaces

1993 ◽  
Vol 308 ◽  
Author(s):  
Y. Chen ◽  
Z. Liliental-Weber ◽  
J. Washburn ◽  
J.F. Klem ◽  
J.Y. Tsao
Keyword(s):  
Strain Relaxation ◽  
Dislocation Line ◽  
Line Tension ◽  
Misfit Strain ◽  
Relaxation Mechanism ◽  
Misfit Dislocations ◽  
Burgers Vector ◽  
Transmission Electron ◽  
Edge Component ◽  
Interfacial Plane

ABSTRACTTransmission electron microscopy is applied to investigate the effect of post-annealing on misfit dislocations in an In0.2Ga0.8As/GaAs(001) heterostructure. An orthogonal array of 60º dislocations along [110] and [110] directions was observed in the interfaces of the samples grown by MBE at 520 ºC. When the as-grown samples were annealed at temperatures ranging from 600 to 800 ºC, the 60º dislocations were gradually reoriented by dislocation reactions occurring at the 90º intersections followed by nonconservative motion driven by dislocation line tension and the residual elastic misfit strain. The final result of this process was a dislocation array lying along [100] and [010] directions. The reoriented u=<100> dislocation has a Burgers vector , which is the same as that of 60º dislocation, but the edge component of its Burgers vector in the (001) interfacial plane is larger than that of 60º dislocation by a factor of , resulting in a greater contribution to elastic strain relaxation. This nonconservative reorientation of 60º dislocations to form the u=<100> dislocations represents a new strain relaxation mechanism in diamond or zinc blende semiconductor heterostructures.

Transmission Electron Diffraction Techniques for NM Scale Strain Measurement in Semiconductors

1995 ◽  
Vol 406 ◽  
Author(s):  
J. Vanhellemont ◽  
K. G. F. Janssens ◽  
S. Frabboni ◽  
P. Smeys ◽  
R. Balboni ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Three Dimensional ◽  
Local Strain ◽  
Quantitative Information ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Convergent Beam

AbstractAn overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.

STRAIN OF GaN LAYERS GROWN USING 6H-SiC(0001) SUBSTRATES WITH DIFFERENT BUFFER LAYERS

2004 ◽  
Vol 14 (01) ◽  
pp. 39-50 ◽  
Author(s):  
S. EINFELDT ◽  
Z. J. REITMEIER ◽  
R. F. DAVIS
Keyword(s):  
Buffer Layer ◽  
Local Strain ◽  
Relaxation Mechanism ◽  
Growth Direction ◽  
Buffer Layers ◽  
Decay Length ◽  
Exponential Dependence ◽  
Misfit Dislocations ◽  
Aln Buffer ◽  
20 Nm

Gallium nitride films of increasing thickness have been grown on either AlN or AlGaN substrates. The state of stress of these biaxially stressed layers gradually changed from compression to tension with regard to both their average strain and their local strain along the [0001] growth direction. The components of both the compressive and tensile stresses are caused by the mismatch in lattice parameters between the GaN and the buffer layer and the mismatch in the coefficients of thermal expansion between GaN and SiC , respectively. The compressive stress is partially relieved within the first 20 nm in the GaN film grown on the AlN buffer layer. The relief of the remaining stress follows an exponential dependence on the thickness of the GaN layer with values for the characteristic decay length of 0.24 μm and 0.64 μm for the AlN and AlGaN buffer layer, respectively. The relaxation mechanism is discussed in terms of the formation of misfit dislocations via surface undulations.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

Tire Modeling by Finite Elements

1992 ◽  
Vol 20 (1) ◽  
pp. 33-56 ◽  
Author(s):  
L. O. Faria ◽  
J. T. Oden ◽  
B. Yavari ◽  
W. W. Tworzydlo ◽  
J. M. Bass ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Rolling Contact ◽  
Test Problems ◽  
State Behavior ◽  
Normal Contact ◽  
New Developments ◽  
Applied Torque ◽  
Dimensional Finite Element ◽  
Tire Modeling ◽  
Three Dimensional Finite Element

Abstract Recent advances in the development of a general three-dimensional finite element methodology for modeling large deformation steady state behavior of tire structures is presented. The new developments outlined here include the extension of the material modeling capabilities to include viscoelastic materials and a generalization of the formulation of the rolling contact problem to include special nonlinear constraints. These constraints include normal contact load, applied torque, and constant pressure-volume. Several new test problems and examples of tire analysis are presented.

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