Stacking Fault Tetrahedra Formation During Growth of Si1-xGex Strained Layers on 〈111〉 Oriented Si Substrates: Tem Observations and Defect Modeling

1994 ◽  
Vol 356 ◽  
Author(s):  
David J. Howard ◽  
Allan F. Bower ◽  
David C. Paine
Keyword(s):  
Strain Energy ◽  
Stacking Fault ◽  
Dislocation Network ◽  
Dislocation Loops ◽  
Strained Layers ◽  
Plan View ◽  
Strained Layer ◽  
Si Substrates ◽  
Stacking Fault Tetrahedra ◽  
Stable Growth

AbstractWe report the observation of stacking fault tetrahedra (SFT) in strained Si1-xGex layers grown via rapid thermal CVD on (111) Si substrates. It is shown that these defects provide a mechanism for strain relief in films strained in compression due the presence of bounding edge-type stair rod partials whose Burgers vectors lie parallel to the strained layer interface. Cross section and plan view TEM were used to characterize this defect structure in epilayers (30 to 650nm thick) of Si1-xGex (0 < xGe < 0.27) grown on 〈111〉 oriented Si wafers. Stacking fault tetrahedra were observed only in alloys in the compositional range xGe ≥ 0.13 and only when growth proceeded on the 〈111〉 surface. A critical strain energy model that identifies conditions for the stable growth of stacking fault tetrahedra in a strained layer is presented. The model was based on conventional strain energy considerations where the energy of the stacking fault area plus the bounding dislocation network (including dislocation interactions but neglecting the free surface) was balanced against the strain energy released by the introduction of the defect. In addition, a formation mechanism consistent with these observations is described that involves the dissociation of Frank partial dislocation loops bounding stacking faults lying in the growth plane.

Observation of Open-Ended Stacking Fault Tetrahedra in Si0.85Ge0.15 Grown on V-Grooved (001) Si and Planar (111) Si Substrates

1993 ◽  
Vol 319 ◽  
Author(s):  
David J. Howard ◽  
David C. Paine
Keyword(s):  
Chemical Vapor ◽  
Stacking Fault ◽  
Line Pattern ◽  
Plan View ◽  
Thermal Chemical Vapor Deposition ◽  
Si Substrates ◽  
Transmission Electron ◽  
Stacking Fault Tetrahedra ◽  
Planar Substrates ◽  
Tem Transmission Electron Microscopy

AbstractA new strain relief mechanism was observed in thin films of Si0.85Ge0.15 grown by RTCVD (rapid thermal chemical vapor deposition) on patterned (001) and planar (111) Si substrates. The (001) Si substrates were lithographically patterned and anisotropically etched to produce a line pattern of V-shaped grooves running in the [110] direction where the walls of the grooves were the {111} crystal planes lying in the [110] zone. Cross-section and plan-view TEM (transmission electron microscopy) studies revealed the presence of open ended stacking fault tetrahedra in strained-layer Si0.85Ge0.15 grown both on (111) Si wafers and the {111} sidewalls of the patterned (001) Si wafers. No defects were observed in the (001) portions of the films grown on non-planar substrates.

Contrast From Point Defects in The Infinitesimal Approximation

1980 ◽  
Vol 38 ◽  
pp. 350-351
Author(s):  
L. J. Sykes ◽  
J. J. Hren
Keyword(s):  
Electron Microscope ◽  
Point Defects ◽  
Broad Class ◽  
Stacking Fault ◽  
Crystalline Solids ◽  
Dislocation Loops ◽  
Analytical Expression ◽  
Stacking Fault Tetrahedra

In electron microscope studies of crystalline solids there is a broad class of very small objects which are imaged primarily by strain contrast. Typical examples include: dislocation loops, precipitates, stacking fault tetrahedra and voids. Such objects are very difficult to identify and measure because of the sensitivity of their image to a host of variables and a similarity in their images. A number of attempts have been made to publish contrast rules to help the microscopist sort out certain subclasses of such defects. For example, Ashby and Brown (1963) described semi-quantitative rules to understand small precipitates. Eyre et al. (1979) published a catalog of images for BCC dislocation loops. Katerbau (1976) described an analytical expression to help understand contrast from small defects. There are other publications as well.

Periodic {001} Walls of Defects in Proton-Irradiated Cu and Ni

1986 ◽  
Vol 82 ◽  
Author(s):  
P. Ehrhart ◽  
W. Jäger ◽  
W. Schilling ◽  
F. Dworschak ◽  
Afaf A. Gadalla ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Average Concentration ◽  
Stacking Fault ◽  
Dislocation Loops ◽  
Transmission Electron ◽  
Stacking Fault Tetrahedra

ABSTRACTThe evolution of the defect structure in 3 MeV-proton irradiated Cu and Ni has been investigated by transmission electron microscopy and by differential dilatometry. The proton irradiations were performed at T≦100°C up to irradiation doses of 2 dpa. An efficient loss of selfinterstitial atoms at dislocations and a consequently high average concentration of vacancies in clusters is observed starting from rather low fluences. In addition an ordering of the defects in the form of periodic {001} walls with a typical periodicity length of ≈ 60 nm is observed for all equivalent {001} planes. The walls consist of high local concentrations of dislocations, dislocation loops and stacking-fault tetrahedra. The observed formation of periodic arraysof defect walls is considered as an example for a possibly general microstructural phenomenon in metals under irradiation.

Electron microscope image contrast of small dislocation loops and stacking-fault tetrahedra

1979 ◽  
Vol 292 (1397) ◽  
pp. 523-537 ◽  
Keyword(s):  
Electron Microscope ◽  
Numerical Solutions ◽  
Preceding Paper ◽  
Stacking Fault ◽  
Image Contrast ◽  
Dislocation Loops ◽  
Displacement Fields ◽  
Microscope Image ◽  
Stacking Fault Tetrahedra ◽  
Electron Microscope Image

With the use of the method described in the preceding paper (to be referred to subsequently as I) for constructing the displacement fields, the electron microscope image contrast of small dislocation loops and of stacking-fault tetrahedra has been computed from numerical solutions of the Howie-Whelan (1961) equations. The computer-simulated images, displayed in the form of half-tone pictures, have been used to identify the nature and geometry of such defects in ion-irradiated foils. A systematic study of the contrast of small Frank loops in Cu + ion irradiated copper under a wide variety of diffraction conditions is reported. In particular the variations of the contrast of loops edge-on and inclined to the electron beam with the operating Bragg reflexion, the thickness and inclination of the foil, depth of the defect in the foil and deviation from the Bragg-reflecting condition have been studied. Methods of obtaining useful information, such as the diameters of the loops, are suggested. The contrast of stacking-fault tetrahedra, and of non-edge perfect dislocation loops in ion-irradiated molybdenum is also investigated.

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-fault tetrahedra in ion-implanted III-V compounds

1987 ◽  
Vol 45 ◽  
pp. 316-317
Author(s):  
B.C. De Cooman ◽  
S. McKeman ◽  
C.B. Carter
Keyword(s):  
Surface Layer ◽  
Solid Phase ◽  
High Resolution Electron Microscopy ◽  
Stacking Fault ◽  
Dislocation Loops ◽  
Present Contribution ◽  
Stacking Fault Tetrahedra ◽  
Type Layer ◽  
Resolution Electron ◽  
Before And After

The implantation of heavy ions into GaAs for the purpose of obtaining a shallow n-type layer has been studied in detail, The results obtained by Rutherford Backscattering and high-resolution electron microscopy show that the surface layer is amorphized during implantation and that the solid-phase epitactic regrowth gives rise to a surface layer containing a large density of microtwins and stacking faults. No other defects have been reported other than interstitial-type dislocation loops in the implanted material, despite the fact that P-implants in Si had shown that a high density of stacking-fault tetrahedra (SFT) were formed after annealing. The present contribution reviews the major findings obtained during the first observation of SFT in Ga1-xAlxAs/GaAs (x=0.3) superlattices and Ga1-xAlxAs (x=0.3) epilayers grown on (001) GaAs. The material was grown by molecular-beam epitaxy (MBE). The ion energy used was 175kV, the dose was 1015 cm-2 and the Se ions were implanted at room-temperature The specimens were examined before and after a 4 hour anneal at 660°C.

In Situ Observations of Misfit Dislocations in Lattice-Mismatched Epitaxial Semiconductor Heterostructures

MRS Bulletin ◽  
1994 ◽  
Vol 19 (6) ◽  
pp. 32-37 ◽  
Author(s):  
Robert Hull ◽  
John Bean
Keyword(s):  
Epitaxial Layer ◽  
Strain Energy ◽  
Experimental Studies ◽  
Elastic Strain Energy ◽  
Lattice Parameter ◽  
Semiconductor Heterostructures ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Strained Layer

This article describes the application of transmission electron microscopy (TEM) to real-time, in situ dynamic observations of dislocations in strained epitaxial semiconductor heterostructures. Such experiments allow us to directly observe the formation, motion, and interaction of mis-fit dislocations. Preliminary extension of this work to the in situ measurement of the electrical properties of misfit dislocations will also be described.The Fundamental Scientific IssueIt is well established that it is possible to grow a thin, coherent epitaxial layer on a substrate with a slightly different lattice parameter, as illustrated in Figure la. This concept is known as strained layer epitaxy. In the fields of semiconductor physics and device design, strained layer epitaxy offers many exciting new opportunities (see Reference 1 for a review). A coherently strained structure, however, will store an enormous elastic strain energy density in the epitaxial layer, due to the distortion of interatomic bonds. Therefore, as the epitaxial layer increases in thickness during growth, it will become increasingly energetically favorable to relax this strain energy. A number of relaxation routes exist: (1) roughening of the epitaxial layer surface (see, for example, Reference 2); (2) interdiffusion of the layers (this will generally only be significant at temperatures which are a large fraction of the layer melting temperatures (e.g., Reference 3)); and (3) introduction of a dislocation network into the substrate/epilayer interface, which as shown schematically in Figure lb, will allow the epitaxial layer to relax toward its bulk lattice parameter. This dislocation mechanism is the most prevalent strain relaxation mechanism at typical crystal growth and processing temperatures, and we concentrate on this mechanism in our experimental studies.

FAULTED DEFECTS AND STACKING-FAULT ENERGY

1967 ◽  
Vol 45 (2) ◽  
pp. 1135-1146 ◽  
Author(s):  
L. M. Clarebrough ◽  
P. Humble ◽  
M. H. Loretto
Keyword(s):  
Direct Methods ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Face Centered Cubic ◽  
Dislocation Loops ◽  
Cubic Metals ◽  
The Third ◽  
Stacking Fault Tetrahedra ◽  
Dislocation Energy ◽  
Face Centered

Four direct methods of obtaining values of stacking-fault energy from observation of faulted defects in pure face-centered cubic metals are discussed. It is shown that there is essential agreement between the method based on the observation of threefold nodes and that based on the observation of triangular Frank dislocation loops and stacking-fault tetrahedra in deformed f.c.c. metals, in the range where both methods are applicable. On the other hand, it is shown that the third method, based on the collapse size of stacking-fault tetrahedra in quenched metals, cannot yield even an upper limit. New experimental results show that the fourth method, based on the annealing rate of faulted loops, is applicable only to metals of high stacking-fault energy and then only if jog nucleation and propagation are not rate controlling; for low stacking-fault energy metals, these factors, together with the dislocation energy, must be considered, and cannot be completely taken into account.

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