Relaxation of Capped Strained Layers Via the Formation of Microtwins

1990 ◽  
Vol 202 ◽  
Author(s):  
D. M. Hwang ◽  
S. A. Schwarz ◽  
T. S. Ravi ◽  
R. Bhat ◽  
C. Y. Chen
Keyword(s):  
Strain Relaxation ◽  
Stacking Fault ◽  
Face Centered Cubic ◽  
Strained Layers ◽  
Strained Layer ◽  
Fundamental Limitations ◽  
Partial Dislocations ◽  
Relaxation Channel ◽  
Kink Model ◽  
Face Centered

ABSTRACTA new strain relief mechanism in epitaxial layers of lattice mismatched face-centered cubic materials is identified using transmission electron microscopy. For an embedded strained layer near its critical thickness, we find that the primary strain-relaxation channel is through the formation of microtwins. A monolayer microtwin (a stacking fault) spanning the strained layer can form when a pair of partial dislocations of the <112> /6 type with antiparallel Burgers vectors are generated inside the strained layer and glide to the opposite interfaces. A series of partial dislocations can result in a microtwin several monolayers thick. For embedded strained layers of materials with small stacking fault energy, the formation of partial dislocation pairs is an energetically-favored strain relaxation channel, as compared to the formation of perfect dislocation pairs in the conventional double-kink model. Therefore, the mechanism proposed here poses fundamental limitations for strained layer device structures.

Stacking Faults in Crystals

1968 ◽  
Vol 26 ◽  
pp. 250-251
Author(s):  
P. C. J. Gallagher
Keyword(s):  
Stacking Faults ◽  
Elastic Equilibrium ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Major Influence ◽  
Face Centered Cubic ◽  
Degree Of Dissociation ◽  
Partial Dislocations ◽  
Layer Structures ◽  
Face Centered

Stacking faults are an important substructural feature of many materials, and have been widely studied in layer structures (e.g. talc) and in crystals with hexagonal and face centered cubic structure. Particular emphasis has been placed on the study of faulted defects in f.c.c. alloys, since the width of the band of fault between dissociated partial dislocations has a major influence on mechanical properties.Under conditions of elastic equilibrium the degree of dissociation reflects the balance of the repulsive force between the partials bounding the fault, and the attractive force associated with the need to minimize the energy arising from the misfits in stacking sequence. Examples of two of the faulted defects which can be used to determine this stacking fault energy, Υ, are shown in Fig. 1. Intrinsically faulted extended nodes (as at A) have been widely used to determine Υ, and examples will be shown in several Cu and Ag base alloys of differing stacking fault energy. The defect at B contains both extrinsic and intrinsic faulting, and readily enables determination of both extrinsic and intrinsic fault energies.

Selected Values for the Stacking Fault Energy of Face Centered Cubic Metals

2008 ◽  
Vol 591-593 ◽  
pp. 708-711 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
High Resolution Electron Microscopy ◽  
Accurate Method ◽  
Stacking Fault ◽  
Metals And Alloys ◽  
Stacking Fault Energy ◽  
Face Centered Cubic ◽  
Resolution Electron ◽  
Plastic Deformation Behavior ◽  
Face Centered ◽  
The 1960S

The Stacking fault energy (SFE) is an important parameter for metals and alloys. The plastic deformation behavior of face centered cubic (FCC) metals and alloys is directly related to the SFE values. The several methods for determining SFE are critically discussed. The values reported in the 1960s and early 1970s are, in general, 20-30% overestimated. The node dislocation method, due to Whelan, overestimates the SFE. The method based on the critical resolved shear stress is not reliable. The most accurate method is the direct observation of dissociated partials by weak beam in TEM or using HREM (High resolution electron microscopy). Indirect methods based in X-Ray Diffraction and texture may provide reasonable estimates since reliable SFE values of reference metals are available. Selected SFE values for Ni, Cu, Ag, Cu and Al are presented.

The Roles of Stress, Geometry and Orientation on Misfit Dislocations Kinetics and Energetics in Epitaxial Strained Layers.

1991 ◽  
Vol 239 ◽  
Author(s):  
R. Hull ◽  
J. C. Bean ◽  
F. Ross ◽  
D. Bahnck ◽  
L. J. Pencolas
Keyword(s):  
Misfit Dislocation ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Slip Systems ◽  
Strained Layers ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Strain Stress ◽  
Kinetics Of

ABSTRACTThe geometries, microstructures, energetics and kinetics of misfit dislocations as functions of surface orientation and the magnitude of strain/stress are investigated experimentally and theoretically. Examples are drawn from (100), (110) and (111) surfaces and from the GexSi1–x/Si and InxGa1–x/GaAs systems. It is shown that the misfit dislocation geometries and microstructures at lattice mismatch stresses < - 1GPa may in general be predicted by operation of the minimum magnitude Burgers vector slipping on the widest spaced planes. At stresses of the order several GPa, however, new dislocation systems may become operative with either modified Burgers vectors or slip systems. Dissociation of totál misfit dislocations into partial dislocations is found to play a crucial role in strain relaxation, on surfaces other than (100) under compressive stress.

Sign in / Sign up

Export Citation Format

Share Document