Critical thickness and stress relaxation in YBaCuO (123) strained epitaxial layers and YBaCuO based strained superlattices

1996 ◽  
Vol 100 (2) ◽  
pp. 185-190 ◽  
Author(s):  
J.P. Contour ◽  
A. Défossez ◽  
D. Ravelosona ◽  
A. Abert ◽  
P. Ziemann
Keyword(s):  
Stress Relaxation ◽  
Critical Thickness ◽  
Epitaxial Layers

Stress Relaxation in Uniquely Oriented SiGe/Si Epitaxial Layers

1999 ◽  
Vol 594 ◽  
Author(s):  
M. E. Ware ◽  
R. J. Nemanich
Keyword(s):  
Stress Relaxation ◽  
Surface Morphology ◽  
Strain Relaxation ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Strained Layers ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Deposited Films

AbstractThis study explores stress relaxation of epitaxial SiGe layers grown on Si substrates with unique orientations. The crystallographic orientations of the Si substrates used were off-axis from the (001) plane towards the (111) plane by angles, θ = 0, 10, and 22 degrees. We have grown 100nm thick Si(1−x) Ge(x) epitaxial layers with x=0.3 on the Si substrates to examine the relaxation process. The as-deposited films are metastable to the formation of strain relaxing misfit dislocations, and thermal annealing is used to obtain highly relaxed films for comparison. Raman spectroscopy has been used to measure the strain relaxation, and atomic force microscopy has been used to explore the development of surface morphology. The Raman scattering indicated that the strain in the as-deposited films is dependent on the substrate orientation with strained layers grown on Si with 0 and 22 degree orientations while highly relaxed films were grown on the 10 degree substrate. The surface morphology also differed for the substrate orientations. The 10 degree surface is relatively smooth with hut shaped structures oriented at predicted angles relative to the step edges.

Bond length variation in In0.25Ga0.75As/InP epitaxial layers thicker than the critical thickness

1999 ◽  
Vol 86 (5) ◽  
pp. 2533-2539 ◽  
Author(s):  
M. Tormen ◽  
D. De Salvador ◽  
M. Natali ◽  
A. Drigo ◽  
F. Romanato ◽  
...  
Keyword(s):  
Bond Length ◽  
Critical Thickness ◽  
Epitaxial Layers ◽  
Length Variation

The Critical Thickness of Layers Subject to Anisotropic Misfit.

1991 ◽  
Vol 239 ◽  
Author(s):  
Richard Beanland
Keyword(s):  
Dislocation Density ◽  
Layer Thickness ◽  
Critical Thickness ◽  
Theoretical Calculations ◽  
Critical Layer ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Critical Layer Thickness ◽  
New Formulation

ABSTRACTIt is well known that it becomes energetically favourable for misfit dislocations to be introduced into strained epitaxial layers above a certain ‘critical’ layer thickness, hc. To date, theoretical calculations of hc have only been made for cases of isotropie misfit - i.e. cases where the misfit is the same for every direction in the interface. Using a new formulation of the Frank-Bilby equation and the concept of coherency dislocations, it is now possible to treat cases of anisotropie misfit, such as silicon on sapphire (SOS). The method used to obtain the critical thickness is described, and values of hc and equilibrium dislocation density are given for various materials systems.

Deep Luminescence from ‘Relaxed’ Si1−xGex Epitaxial Layers

1991 ◽  
Vol 220 ◽  
Author(s):  
Gordon Davies ◽  
Victor Higgs ◽  
Richard Kubiak ◽  
Adrian Powell ◽  
Terry Whall ◽  
...  
Keyword(s):  
Diagnostic Tool ◽  
Critical Thickness ◽  
Epitaxial Layers ◽  
X Rays ◽  
Dislocation Related Luminescence

ABSTRACTIn MBE Si1−xGex which is grown to thicknesses greater than the critical thickness hc, the dislocation-related luminescence peaks Dl and D2 have energies which are independent of x up to x ≈ 0.3, and then decrease, as observed in LPE Si1−xGex. In MBE Si1−xGex layers grown to thicknesses less than hc, post-growth annealing produces dramatic changes in the luminescence, giving spectra as from relaxed alloy, even though the relaxation determined by X-rays is negligible. These results establish photoluminescence as a sensitive diagnostic tool for detecting dislocations in Si1−xGe*.

Strained Layer Epitaxy on Rough Si Surfaces

1995 ◽  
Vol 379 ◽  
Author(s):  
T.D. Lowes ◽  
M. Zinke-Allmang
Keyword(s):  
Epitaxial Layer ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Rough Surfaces ◽  
Misfit Strain ◽  
Surface Roughening ◽  
Epitaxial Layers ◽  
Dislocation Generation ◽  
Surface Features ◽  
Initial Substrate

ABSTRACTLattice mismatch associated with heteroepitaxy imposes a significant limitation on the epitaxial compatibility between overlayer and substrate. In lattice mismatched systems the misfit may be accommodated to some extent by strain. However, in order to maintain misfit strain and avoid dislocation generation the epitaxial layer must not exceed a critical thickness. Some success has been reported in avoiding damaged epitaxial layers with thicknesses greater than the critical thickness by overgrowing on patterned or rough surfaces. For the case of Si, surface roughening by energetic Ar+ bombardment as a pre-growth roughening treatment is discussed and assessed. Evolution of surface features as a function of initial substrate treatment, ion accelerating potential, and the duration of bombardment are presented. Stability of the surface features generated by bombardment for typical overgrowth conditions was tested to assess feasibility of this technique for Si heteroepitaxy.

scholarly journals Theoretical research on critical thickness of HgCdTe epitaxial layers

2005 ◽  
Vol 54 (12) ◽  
pp. 5814
Author(s):  
Wang Qing-Xue ◽  
Yang Jian-Rong ◽  
Wei Yan-Feng
Keyword(s):  
Critical Thickness ◽  
Theoretical Research ◽  
Epitaxial Layers

The Morphological Stability of Strained Epitaxial Layers

1996 ◽  
Vol 440 ◽  
Author(s):  
B. W. Wessels
Keyword(s):  
Thin Films ◽  
Critical Thickness ◽  
Strain Relaxation ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Epitaxial Layers ◽  
Two Dimensional ◽  
Morphological Stability

AbstractThe morphological stability of strained-layer thin films is analyzed using classical nucleation theory. For the case where strain relaxation occurs by formation of coherent islands, the model predicts that the critical thickness for transition from two-dimensional (2D) to three dimensional (3D) growth depends inversely on the square of the misfit. The predicted dependence of critical thickness on misfit is in agreement with recent experimental studies on the heteropitaxy of III-V compounds.

The Evolution of Strain Relaxation Close to The Critical Thickness

1993 ◽  
Vol 317 ◽  
Author(s):  
P. Kidd ◽  
P.F. Fewster
Keyword(s):  
Residual Strain ◽  
Strain Field ◽  
Critical Thickness ◽  
Strain Relaxation ◽  
Epitaxial Layers ◽  
X Ray Diffraction ◽  
Strain Fields ◽  
X Ray ◽  
Local Relaxation ◽  
Homogeneous Strain

ABSTRACTHigh resolution X-ray diffraction space mapping has been used to follow the change in the distribution of residual strain and localised relaxation in low mismatched epitaxial layers. Using this new technique, we have obtained a series of diffraction space maps of partially relaxed epitaxial layers of In.1Ga.9As on GaAs. The layers have different thicknesses and hence different degrees of strain relaxation. The diffuse scatter close to the Bragg peaks provides information about the imperfect and distorted regions in the structure and this has allowed us to examine the extent and distribution of residual strain close to the dislocations. We have followed the evolution of local relaxation, which is confined initially to regions around isolated dislocations, through to the case of overlapping dislocation strain fields, leading to a more homogeneous strain field distribution and microscopic and macroscopic tilting of the layers.

scholarly journals Atomic diffusion induced by stress relaxation in InGaAs/GaAs epitaxial layers

1997 ◽  
Vol 82 (3) ◽  
pp. 1147-1152 ◽  
Author(s):  
P. Roura ◽  
A. Vilà ◽  
J. Bosch ◽  
M. López ◽  
A. Cornet ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Atomic Diffusion ◽  
Epitaxial Layers
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