Strain Relaxation in Thin Films: the Effect of Dislocation Blocking

1999 ◽  
Vol 594 ◽  
Author(s):  
Peter J Goodhew
Keyword(s):  
Thin Films ◽  
Experimental Evidence ◽  
Strain Relaxation ◽  
Dislocation Line ◽  
Small Strain ◽  
Threading Dislocations ◽  
Semiconductor Films ◽  
Strained Layers ◽  
Dislocation Configuration ◽  
Perpendicular Line

AbstractThe relaxation of strained layers frequently occurs by the glide of threading dislocations. From very early on in the relaxation process, gliding dislocations will be forced to intersect a number of prior dislocations with almost-perpendicular line directions and their progress may be blocked. This effect has been widely reported in semiconductor films, and there is some experimental evidence that it is reduced when layers are grown on vicinal substrates. This implies that the blocking is sensitively dependent on the dislocation configuration and in particular on the dislocation line directions.In this paper the interactions between gliding threading dislocations and the perpendicular or nearly-perpendicular dislocation in their path are modelled quantitatively. The differences arising from different initial dislocation configurations and different predominant line directions are found to be small. Strain relaxation, at least in its early stages, should be virtually independent of the initial dislocation configuration.

Effects of Stress on Step Energies and Surface Roughness

MRS Bulletin ◽  
1996 ◽  
Vol 21 (4) ◽  
pp. 27-30 ◽  
Author(s):  
Christopher Roland
Keyword(s):  
Thin Films ◽  
Strain Relaxation ◽  
Three Dimensional ◽  
Layer Growth ◽  
Growth Mode ◽  
Misfit Dislocations ◽  
Layer By Layer ◽  
Strained Layers ◽  
The Subject ◽  
Growth Changes

Strain relaxation in lattice-mismatched, heteroepitaxial systems is one of the classic problems in materials physics, which has gained new urgency with the increased applications of strained layers in microelectronic systems. In general both the structure and the integrity of the thin films are strongly influenced by strain. For instance it has long been known that under strain, the growth changes from an initial layer-by-layer growth mode to one with three-dimensional islanding. In the seminal works of van der Merwe, and Matthews and Blakeslee, this change in growth mode is explained in terms of the introduction of strain-relieving misfit dislocations, which appear when the film has reached some critical thickness. Recently it has become clear that this change in growth mode can take place even without the introduction of misfit dislocations. Such dislocation-free coherent islanding, or “roughening,” has been observed experimentally both in Ge/Si and in InGaAs/GaAs systems. Furthermore recent experiments show that in Ge/Si(100) systems, the thin films display a curious asymmetry with respect to the sign of the strain: Films under compression roughen by forming coherent islands while those under tension remain relatively smooth. A possible mechanism behind this strain-induced type of roughening is the subject of this article.

Very Thick Coherently Strained GexSi1−x Layers Grown in a Narrow Temperature Window

1991 ◽  
Vol 220 ◽  
Author(s):  
C. H. Chern ◽  
K. L. Wang ◽  
G. Bai ◽  
M. -A. Nicolet
Keyword(s):  
Growth Temperature ◽  
Strain Relaxation ◽  
Gas Pressure ◽  
High Density ◽  
Misfit Dislocations ◽  
High Quality ◽  
Strained Layers ◽  
Temperature Window ◽  
Residual Gas

ABSTRACTStrain relaxation of GexSi1−x layers is studied as a function of growth temperature. Extremely thick coherently strained layers whose thicknesses exceed more than fifty times of the critical thicknesses predicted by Matthews and Blakeslee's model were successfully grown by MBE. There exits a narrow temperature window from 310 °C to 350 °C for growing this kind of high quality thick strained layers. Below this temperature window, the layers are poor in quality as indicated from RHEED patterns. Above this window, the strain of the layers relaxes very fast accompanied with a high density of misfit dislocations as the growth temperature increases. Moreover, for samples grown in this temperature window, the strain relaxation shows a dependence of the residual gas pressure, which has never been reported before.

Short-period (Si14 / Si0.75 Ge0.25)20 Superlattices for the Growth of High-quality Si0.75 Ge0.25

2003 ◽  
Vol 765 ◽  
Author(s):  
M.M. Rahman ◽  
T. Tambo ◽  
C. Tatsuyama
Keyword(s):  
Low Temperature ◽  
Alloy Layer ◽  
Buffer Layers ◽  
Threading Dislocations ◽  
Strained Layers ◽  
Temperature Growth ◽  
Low Temperature Growth ◽  
Defect Sites ◽  
Short Period ◽  
Different Temperatures

AbstractIn the present experiment, we have grown 2500-Å thick Si0.75Ge0.25 alloy layers on Si(001) substrate by MBE process using a short-period (Si14/Si0.75Ge0.25)20 superlattice (SL) as buffer layers. In the SL layers, first a layer of 14 monolayers (MLs) of Si (thickness about 20Å) then a thin layer of Si0.75Ge0.25 (thickness 5-6Å) were grown. This Si/(Si0.75Ge0.25) bilayers were repeated for 20 times. The buffer layers were grown at different temperatures from 300-400°C and the alloy layers were then grown at 500°C on the buffer layers. The alloy layer showed low residual strain (about -0.16%) and smooth surface (rms roughness ~15Å) with 300°C grown SL buffer. Low temperature growth of Si in SL layer introduces point defects and low temperature growth of Si1-xGex in SL layer reduces the Ge segregation length, which leads to strained SL layer formation. Strained layers are capable to make barrier for the propagation of threading dislocations and point defect sites can trap the dislocations.

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.

Effect of strain relaxation of oxidation-treated SiGe epitaxial thin films and its nanomechanical characteristics

2010 ◽  
Vol 256 (10) ◽  
pp. 3299-3302 ◽  
Author(s):  
Bo-Ching He ◽  
Hua-Chiang Wen ◽  
Tun-Yuan Chinag ◽  
Zue-Chin Chang ◽  
Derming Lian ◽  
...  
Keyword(s):  
Thin Films ◽  
Strain Relaxation ◽  
Epitaxial Thin Films

scholarly journals Role of threading dislocations in strain relaxation during GaInN growth monitored by real-time X-ray reflectivity

2017 ◽  
Vol 110 (26) ◽  
pp. 262105 ◽  
Author(s):  
Guangxu Ju ◽  
Masao Tabuchi ◽  
Yoshikazu Takeda ◽  
Hiroshi Amano
Keyword(s):  
Real Time ◽  
Strain Relaxation ◽  
Threading Dislocations ◽  
X Ray

Time-Resolved Reflectivity Study of Solid-Phase Epitaxial Regrowth in Relaxed and Strained Si1−xGex Epilayers

1992 ◽  
Vol 281 ◽  
Author(s):  
T. E. Haynes ◽  
C. Lee ◽  
K. S. Jones
Keyword(s):  
Composition Dependence ◽  
Solid Phase ◽  
Strain Relaxation ◽  
Alloy Layer ◽  
Atomic Fraction ◽  
Bulk Alloy ◽  
Strained Layers ◽  
Time Resolved ◽  
Epitaxial Regrowth ◽  
Different Types

ABSTRACTThe rate of solid-phase epitaxial regrowth has been studied using time-resolved reflectivity in three different types of SiGe/Si epilayers amorphized by ion implantation. In two of these cases, the alloy epilayer contained either 12% or 20% Ge, and the amorphization depth was greater than the thickness (2000 Å) of the SiGe alloy layer. Time-resolved reflectivity measurements showed that the rate of regrowth was not constant in these two cases, but first decreased after passing the SiGe/Si interface, and then increased. The minimum regrowth rate occurred closer to the SiGe/Si interface in the epilayers with the larger Ge atomic fraction. In the third type of sample, the alloy epilayer thickness was ∼7μm, so that the initial epilayer (15% Ge) had the lattice constant of the bulk alloy. Furthermore, amorphization and regrowth occurred entirely within the relaxed alloy layer. In this case, the regrowth rate was constant. The composition dependence of the regrowth-rate transient in the strained layers is discussed in the context of a ‘critical-thickness’ model of strain relaxation.

Strain relaxation and formation of $a$-domain for PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$ thin films epitaxially grown on SrTiO$_{3}$ substrate

2009 ◽  
Vol 55 (4) ◽  
pp. 1327-1330 ◽  
Author(s):  
Bog G Kim ◽  
Daeyoung Kwon ◽  
Bongju Kim ◽  
Chang Hwan Chang
Keyword(s):  
Thin Films ◽  
Strain Relaxation
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