Misfit Dislocations at II-VI/GaAs Interfaces

1990 ◽  
Vol 183 ◽  
Author(s):  
A. F. Schwartzman
Keyword(s):  
Lattice Mismatch ◽  
High Resolution Electron Microscopy ◽  
Interfacial Structure ◽  
Misfit Dislocations ◽  
Extended Defects ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
Before And After ◽  
Slip Planes ◽  
Efficient Type

AbstractHigh-resolution electron microscopy -is used to characterize the defect structure of CdTe/GaAs and ZnTe/GaAs heterojunctions before and after annealing. For as-deposited films, a variety of defects exist both in the form of perfect misfit dislocations at the interface and extended defects into the thin film. The extended defects result from dissociation of 60° dislocations and reactions between perfect and partial dislocations lying on intersecting slip planes. The annealed interfaces consist of a periodic array of perfect edge Lomer dislocations, the most efficient type of misfit dislocation for accomodating the lattice mismatch, 14.6 % for CdTe/GaAs and 8 % for ZnTe/GaAs. In both cases, the spacing between dislocations corresponds to the value predicted for completely strain-free thin fims, 31 and 54 Å for CdTe and ZnTe respectively. This paper concentrates on the different dislocation reactions which transform the interfacial structure from the as-deposited case to the annealed case.

HIGH RESOLUTION ELECTRON MICROSCOPE STUDY OF CdTe-Cd0.6Mn0.4 Te SUPERLATTICES

1985 ◽  
Vol 56 ◽  
Author(s):  
C. CHOI ◽  
N. OTSUKA ◽  
L. A. KOLODZIEJSKI ◽  
R. L. GUNSHOR-a
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Contrast ◽  
Electron Microscope Study ◽  
Lattice Mismatch ◽  
Thick Layer ◽  
High Resolution Electron Microscopy ◽  
Misfit Dislocations ◽  
Resolution Electron ◽  
High Resolution Electron Microscope

AbstractStructures of CdTe-Cd0.6Mn0.4Te superlattices which are caused by the lattice mismatch between suterlattice layers have been studied by high resolution electron microscopy (HREM). In thin-layer superlattices, the crystal lattice in each layeris elastically distorted, resulting in the change of the crystal symmetry from cubic to rhombohedral. The presence of the small rhombohedral distrotion has been confirmed through a phase contrast effect in HREM images. In a thick-layer superlattice, the lattice mismatch is accommodated by dissociated misfit dislocations. Burgers vectors of partial misfit dislocations have been identified from the shift of lattice fringes in HREM images.

Epitaxial Growth and Structure of Cubic and Pseudocubic Perovskite Films on Perovskite Substrates

1995 ◽  
Vol 401 ◽  
Author(s):  
P. A. Langjahr ◽  
T. Wagner ◽  
M. RÜhle ◽  
F. F. Lange
Keyword(s):  
Electron Microscopy ◽  
Epitaxial Growth ◽  
Lattice Mismatch ◽  
High Resolution Electron Microscopy ◽  
Lattice Parameter ◽  
Ternary Oxide ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Resolution Electron

AbstractCubic and pseudocubic perovskite films on perovskite substrates are used to study the influence of the lattice mismatch on the epitaxial growth of thin films on substrates of the same structure. For the growth of the films, a metalorganic decomposition route (MOD) using 2-ethylhexanoates and neodecanoates as precursors, was developed. The decomposition of the precursors was investigated with thermogravimetric analysis (TGA) and x-ray diffraction (XRD). The films were spin-coated on (001)-oriented SrTiO3- and LaAlO3-substrates, pyrolyzed and afterwards annealed between 600°C and 1200°C. XRD-nvestigations and conventional transmission electron microscopy (CTEM) show, that epitaxial films with the orientation relationship [100](001) film ║ [100](001) substrate can be grown. With XRD, it could be shown, that not only ternary oxide films (SrZrO3, BaZrO3 and BaCeO3), but also perovskite solid solution films (SrTi0.5Zr0.5O3and BaCe0.5Zr0.5O3) can be prepared. Strong interdiffusion, detected by a shift of the film lattice parameter towards the substrate lattice parameter was found in SrZrO3- and BaZrO3-films on SrTiO3, annealed at temperatures above 1050°C. High resolution electron microscopy (HREM) studies of SrZrO3 on SrTiO3 show that a crystalline semicoherent interface with a periodical array of misfit dislocations is present.

Misfit Dislocations at Metal/Ceramics Interfaces

1993 ◽  
Vol 319 ◽  
Author(s):  
G. Gutekunst ◽  
J. Mayer ◽  
M. RÜHle
Keyword(s):  
Lattice Mismatch ◽  
High Resolution Electron Microscopy ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Burgers Vector ◽  
Resolution Electron ◽  
Substrate Surfaces ◽  
Atomistic Structure ◽  
Good Agreement

AbstractThe atomistic structure of the coherent regions of Nb/A12O3-interfaces of various substrate orientations have been determined by high-resolution electron microscopy (HREM). The substrate surfaces were parallel to (0001)A12O3, (0110)A12O3, (2110)A12O3 and (0112)A12O3. In all cases, the Al sublattice of the A12O3 substrate is continued in the first Nb layer at the interface. This principle results in the unique orientation relationship.The Burgers vectors of the misfit dislocations and the geometry of the dislocation network of all Nb/A12O3-interfaces have been determined by HREM. All Burgers vectors are lattice vectors. Thus no coherent regions with different atomistic structures are found. The Burgers vectors are of the type 1/2<111>. These Burgers vectors correspond to the Burgers vector of bulk dislocations. All Burgers vector components which do not accommodate the lattice mismatch are compensated in the networks. The network geometry is rectangular for the following interface planes: (0110)A12O3||(112)Nb (orientation 2) and (0112)A12O3||(001)Nb. If the interface is parallel to (0001)A12O3 and (111)Nb the geometry is rhombic.The core structure of misfit dislocations of orientation 2 with line direction ξ1=[110] are calculated with an atomistic model and a continuum approach. The calculated core structures are in good agreement with the experimental HREM-micrographs of misfit dislocations of orientation 2.

HRTEM simulation of interfacial structure in amorphous multilayers

1989 ◽  
Vol 47 ◽  
pp. 466-467
Author(s):  
Margaret L. Sattler ◽  
Michael A. O'Keefe
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Cross Section ◽  
High Resolution Electron Microscopy ◽  
Interfacial Structure ◽  
Multilayer Sample ◽  
Resolution Electron ◽  
Multilayered Materials ◽  
Simulated Images

Multilayered materials have been fabricated with such high perfection that individual layers having two atoms deep are possible. Characterization of the interfaces between these multilayers is achieved by high resolution electron microscopy and Figure 1a shows the cross-section of one type of multilayer. The production of such an image with atomically smooth interfaces depends upon certain factors which are not always reliable. For example, diffusion at the interface may produce complex interlayers which are important to the properties of the multilayers but which are difficult to observe. Similarly, anomalous conditions of imaging or of fabrication may occur which produce images having similar traits as the diffusion case above, e.g., imaging on a tilted/bent multilayer sample (Figure 1b) or deposition upon an unaligned substrate (Figure 1c). It is the purpose of this study to simulate the image of the perfect multilayer interface and to compare with simulated images having these anomalies.

Fine structure and properties of defects in naturally occurring silicates and oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 460-461
Author(s):  
David R. Veblen
Keyword(s):  
Chemical Reactions ◽  
High Resolution Electron Microscopy ◽  
Extended Defects ◽  
Single Chain ◽  
Naturally Occurring ◽  
Resolution Electron ◽  
Fine Structures ◽  
Image Simulations ◽  
Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

EPITAXY OF CdTe ON (100) GaAs

1985 ◽  
Vol 56 ◽  
Author(s):  
L. A. KOLODZIEJSKI ◽  
R. L. GUNSHOR ◽  
N. OTSUKA ◽  
C. CHOI
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Strong Interaction ◽  
Gaas Substrate ◽  
Specific Growth ◽  
Lattice Mismatch ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Selection Of

AbstractTwo epitaxial orientations [(111) and (100)] of CdTe are grown on (100) GaAs in the presence of a 14.6% lattice mismatch. Consistent nucleation of a selected orientation is achieved by employing specific growth techniques. The growth techniques for selection of both orientations are described. High resolution electron microscopy has been used to investigate the interface between the CdTe epilayer and the GaAs substrate. For the (111) orientation strong interaction exists between the epitaxial deposit and the substrate, whereas a weakened interaction between deposit and substrate induces the (100) orientation.

Crystal Structure of and Defects in the Pentacene Thin Film Phase

2002 ◽  
Vol 734 ◽  
Author(s):  
Lawrence F. Drummy ◽  
Paul K. Miska ◽  
David C. Martin
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Low Voltage ◽  
Field Effect Transistors ◽  
High Resolution Electron Microscopy ◽  
Orthorhombic Symmetry ◽  
Extended Defects ◽  
X Ray Diffraction ◽  
Voltage Electron ◽  
Resolution Electron

The aromatic hydrocarbon pentacene is currently under investigation for use as the active layer in electronic devices such as thin film field effect transistors. We have used X-Ray Diffraction (XRD), Electron Diffraction (ED), Low Voltage Electron Microscopy (LVEM), High Resolution Electron Microscopy (HREM) and molecular modeling to investigate the thin film phase of pentacene. We will report the orthorhombic symmetry and lattice parameters of the thin film phase measured experimentally from these techniques. The structure of extended defects such as dislocations and grain boundaries will influence the electrical and mechanical characteristics of the films. Here we show a direct image of an edge dislocation in the thin film phase and discuss the way in which the lattice accommodates the defect.

High-resolution electron microscopy of epitaxial YBCO/Y2O3/YSZ on Si(001)

1993 ◽  
Vol 8 (9) ◽  
pp. 2112-2127 ◽  
Author(s):  
A. Bardal ◽  
O. Eibl ◽  
Th. Matthée ◽  
G. Friedl ◽  
J. Wecker
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Thick Layer ◽  
Atomic Layer ◽  
High Resolution Electron Microscopy ◽  
Stacking Fault ◽  
Buffer Layers ◽  
Misfit Dislocations ◽  
Resolution Electron ◽  
Unit Cells

The microstructures of YBa2Cu3O7−δ (YBCO) thin films grown on Si with Y-stabilized ZrO2 (YSZ) and Y2O3 buffer layers were characterized by means of high-resolution electron microscopy. At the Si–YSZ interface, a 2.5 nm thick layer of regrown amorphous SiOx is present. The layer is interrupted by crystalline regions, typically 5 to 10 nm wide and 10 to 50 nm apart. Close to the crystalline regions, {111} defects are present in the Si substrate. The typical defect observed is an extrinsic stacking fault plus a perfect dislocation close to the stacking fault which terminates extra {111} planes in the upper part of the Si. These defects are probably formed by condensation of Si self-interstitials created during oxide regrowth. Precipitates are present in the Si close to the Si–YSZ interface and indicate that in-diffusion of Zr has occurred. The YSZ–Y2O3 interface is atomically sharp and essentially planar and contains no second phases. Perfect misfit dislocations with Burgers vector 1/2〈110〉 are present at this interface along with unrelaxed elastic misfit stresses. The Y2O3–YBCO interface is atomically sharp and planar, but contains steps. (001) stacking faults are present in the YBCO above these steps; the faults are, however, healed a few unit cells away from the interface. By HREM analysis of ultrathin specimen areas, the atomic layer of the YBCO closest to the Y2O3 was found to be a barium-oxygen layer.

High resolution electron microscopy of misfit dislocations in the GaAs/Si epitaxial interface

1986 ◽  
Vol 49 (5) ◽  
pp. 277-279 ◽  
Author(s):  
N. Otsuka ◽  
C. Choi ◽  
Y. Nakamura ◽  
S. Nagakura ◽  
R. Fischer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Misfit Dislocations ◽  
Resolution Electron ◽  
Epitaxial Interface

Microstructure of Epitaxial Al(111)/Si(111) Films Studied by Synchrotron Grazing Incidence X-Ray Diffraction

1990 ◽  
Vol 202 ◽  
Author(s):  
H. H. Hung ◽  
K. S. Liang ◽  
C. H. Lee ◽  
T.-M. Lu
Keyword(s):  
Annealed Film ◽  
Grazing Incidence ◽  
Misfit Strain ◽  
Interfacial Structure ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Incommensurate Structure ◽  
Before And After ◽  
Beam Deposition

ABSTRACTWe report the results of our x-ray diffraction studies on epitaxial Al(111)/Si(111) films prepared by the partially ionized beam deposition technique. Significant changes were observed in intensity profiles for samples before and after annealing. In the in-plane radial scan of Al(220) peak, the shift of Bragg peak is shown due to misfit strain. A weak satellite is also observed which indicates a semicoherent interfacial structure of the annealed film with misfit dislocations. A possible picture of misfit-induced incommensurate structure of Al films is discussed.

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