scholarly journals Defects In GaAs Bulk Crystals and Multi-Layers Caused by In Diffusion

1993 ◽  
Vol 309 ◽  
Author(s):  
P. Werner ◽  
Z. Liliental-Weber ◽  
W. Swider ◽  
H. Sohn ◽  
WaiFan Yau ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Lattice Strain ◽  
Molecular Beam Epitaxy Growth ◽  
Misfit Dislocations ◽  
Bulk Crystals ◽  
Bulk Gaas ◽  
Transmission Electron ◽  
Show Evidence ◽  
Gaas Buffer Layer ◽  
Rapid Diffusion

AbstractThe objective of this work was to study by transmission electron microscopy the lattice defects in GaAs bulk crystals and heterostructures formed by In diffusion. In such samples hints for the existence of superconductivity have been found. Indium was found to move more than 100 μm into bulk GaAs during lh annealing at 550ºC (such conditions are typical for molecular beam epitaxy growth on GaAs wafers). This rapid diffusion is accompanied by the creation of dislocation networks and metallic In droplets that show evidence for lattice strain. To study the interaction of In with the GaAs lattice, In/GaAs multi-layers were grown by MBE at about 450ºC on a GaAs buffer layer. The interfaces of these structures showed misfit dislocations at islands of InAs besides the presence of lattice strain. Both types of samples showed microwave absorption signals typical for superconductivity. The most likely superconductive phases are small metastable inclusions, probably consisting of amorphous Ga or In.

scholarly journals Anisotropic Strain on GaN Microdisks Grown by Plasma-Assisted Molecular Beam Epitaxy

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 899
Author(s):  
Hong-Yi Yang ◽  
Ikai Lo ◽  
Cheng-Da Tsai ◽  
Ying-Chieh Wang ◽  
Huei-Jyun Shih ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Lattice Strain ◽  
Lattice Mismatch ◽  
Lattice Relaxation ◽  
Lattice Constants ◽  
Anisotropic Strain ◽  
Transmission Electron ◽  
Quadratic Deviation

Lattice relaxation on wurtzite GaN microdisks grown by plasma-assisted molecular beam epitaxy was systematically studied. The lattice constants of GaN microdisks were evaluated from high-resolution transmission electron microscopy, and the anisotropic strain was then analyzed by observing the microscopic atomic layers. We found that the vertical lattice strain along the c-axis followed a linear relationship, while the lateral lattice strain along the a-axis exhibited a quadratic deviation. The lattice mismatch is about 0.94% at the interface between the GaN microdisks and the γ-LiAlO2 substrate, which induces the anisotropic strain during epi-growth.

Structural properties of molecular beam epitaxy grown Ni/Pt superlattices

1997 ◽  
Vol 12 (1) ◽  
pp. 161-174 ◽  
Author(s):  
W. Staiger ◽  
A. Michel ◽  
V. Pierron-Bohnes ◽  
N. Hermann ◽  
M. C. Cadeville
Keyword(s):  
Molecular Beam ◽  
Growth Direction ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
Plan View ◽  
X Ray ◽  
Transmission Electron ◽  
Superlattice Peak ◽  
Diffraction Peaks ◽  
Diffraction Patterns

We find that the [Ni3.2nmPt1.6nm] × 15 and [Ni3.2nmPt0.8nm] × 15 multilayers are semicoherent and display a columnar morphology. From both the period of the moir’e fringes and the positions of the diffraction peaks in electronic (plan-view and crosssection geometries) and x-ray diffraction patterns, one deduces that the nickel is relaxed (at least in the error bars of all our measurements), whereas the platinum remains slightly strained (≈−1%). The interfaces are sharp; no intermixing takes place giving rise to neat contrasts in transmission electron microscopy (TEM) and to high intensities of the superlattice peaks in the growth direction in both diffraction techniques. The relaxation of the interfacial misfit occurs partially through misfit dislocations, partially through the strain of platinum. A quasiperiodic twinning occurs at the interfaces, the stacking fault which forms the twin being the most often located at the interface Pt/Ni, i.e., when a Pt layer begins to grow on the Ni layer. The simulation of the θ/2θ superlattice peak intensities takes into account the columnar microstructure. It shows that the roughness is predominantly at medium scale with a fluctuation of about 12.5% for Ni layers and negligible for Pt layers.

High Resolution Transmission Electron Microscopy of PbTe/Pb1-zEuxSeyTe1-v, Heterostructures.

1986 ◽  
Vol 77 ◽  
Author(s):  
L. Salamanca-Young ◽  
D. L. Partin ◽  
J. Heremans ◽  
E. M. Dresselhaus
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam ◽  
Computing Methods ◽  
Misfit Dislocations ◽  
Structural Perfection ◽  
Superlattice Structure ◽  
Transmission Electron ◽  
Simulated Images

ABSTRACTHigh resolution transmission electron microscopy has been used to study the structure of PbTe/Pb1-zEuxSeyTe1-v semiconductor superlattices and heterojunctions grown on BaF2 substrates by molecular beam epitaxy. The objective of this study is to analyze the interface sharpness and the structural perfection of the samples at their interfaces. In the PbTe/Pb1-zEuxSeyTe1-v system, we have observed misfit dislocations and even amorphous regions for high Eu concentrations. We have also observed two directions of growth of the superlattice film. The interface appears to be sharp to approximately three monolayers. A model for the superlattice structure is suggested and used to obtain simulated images using computing methods. The simulated images are compared with those obtained experimentally.

Structural Characterization of Fe3O4–NiO Superlattices Using High-reSolution Transmission Electron Microscopy

1997 ◽  
Vol 12 (8) ◽  
pp. 2143-2151 ◽  
Author(s):  
A. Rečnik ◽  
D. L. Carroll ◽  
K. A. Shaw ◽  
D. M. Lind ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam ◽  
Spin Exchange ◽  
Magnetic Ordering ◽  
Misfit Dislocations ◽  
Transmission Electron ◽  
High Degree

Superlattices of Fe3O4–NiO layers have been studied by high-resolution transmission electron microscopy (HRTEM). These superlattices are grown by oxygen-plasma-assisted molecular-beam epitaxy (MBE) on (001) oriented MgO substrates, and exhibit a high degree of ordering at the interfaces between the interlayers. The lack of misfit dislocations at the Fe3O4–NiO interfaces suggeststhat lattice strain is largely accommodated by changes in the lattice spacing. By quantitative HRTEM analysis of Fe3O4–NiO interfaces, possible atomic models are discussed, having implications in magnetic ordering and spin exchange mechanisms for such interlayer systems.

Generation and Suppression of Stacking Faults in Gap Layers Grown on Si(100) Substrates by Molecular Beam Epitaxy and Migration Enhanced Epitaxy

1996 ◽  
Vol 441 ◽  
Author(s):  
Y. Takagi ◽  
H. Yonezu ◽  
K. Samonji ◽  
T. Tsuji ◽  
N. Ohshima
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Stacking Faults ◽  
Misfit Dislocations ◽  
Generation Process ◽  
Si Substrates ◽  
Transmission Electron ◽  
Migration Enhanced Epitaxy ◽  
Regular Network ◽  
And Migration

AbstractWe have investigated the generation process of crystalline defects in GaP layers grown on Si substrates (GaP/Si) by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). Transmission electron microscopy observations revealed that a regular network of misfit dislocations was generated in GaP/Si by MEE. On the other hand, threading dislocations as well as interfacial misfit dislocations were observed in GaP/Si by MBE. Moreover, stacking faults were generated in high density at the hetero-interface of GaP/Si by MBE. The density of stacking faults was drastically reduced by MEE.

scholarly journals GaN and InGaN Nanowires on Si Substrates by Ga-Droplet Molecular Beam Epitaxy

2008 ◽  
Vol 1080 ◽  
Author(s):  
Kevin Goodman ◽  
Kejia Wang ◽  
Xiangning Luo ◽  
John Simon ◽  
Tom Kosel ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Growth Conditions ◽  
Molecular Beam Epitaxy Growth ◽  
Growth Time ◽  
Band Edge Emission ◽  
Si Substrates ◽  
Gan Nanowires ◽  
Transmission Electron ◽  
Microscopy Images

ABSTRACTMolecular beam epitaxy growth of GaN and InGaN nanowires is accomplished on Si (111) substrates using Ga-droplet nucleation. Typical diameters range from 25-80 nm and lengths can be varied by increasing the growth time; the growth rate is ∼0.25 microns/hour. The nanowires have been characterized structurally and optically. Photoluminescence spectra show band-edge emission of GaN nanowires centered at 362 nm at 290 K. Transmission electron microscopy images unveil that the nanowires are highly crystalline, and grow along the 0001 polar direction. Indium has also been successfully incorporated into GaN nanowires by modifying the growth conditions; the InGaN nanowires emit at ∼520 nm, which provides a possible route to solving strain related problems of high In-composition InGaN based efficient green emitters.

Strain-Field Induced Crosshatch Formation During Molecular Beam Epitaxy of InGaAs/GaAs Films

1993 ◽  
Vol 312 ◽  
Author(s):  
X. C. Zhou ◽  
J. Jiang ◽  
A. Y. Du ◽  
J. W. Zhao ◽  
S. M. Mu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Direct Evidence ◽  
Surface Strain ◽  
Misfit Dislocations ◽  
Strain Fields ◽  
Transmission Electron ◽  
Gaas Films ◽  
Reflection Electron Microscopy

AbstractUsing reflection electron microscopy (REM), transmission electron microscopy (TEM), and Nomarski optical microscopy we obtained direct evidence that local surface strain-fields, originated from misfit dislocations, are responsible for the formation of morphological crosshatches during molecular beam epitaxy of lattice mismatched InGaAs/GaAs layers. A mechanism is proposed to correlate the formation of the crosshatched patterns with the variation of the growth rate across the epitaxial surface under the perturbation of network shaped strain-fields in the surface.

Misfit Dislocations at Mismatched Epitactic Heterojunctions

1990 ◽  
Vol 198 ◽  
Author(s):  
Jane G. Zhu ◽  
C. Barry Carter ◽  
Chris J. Palmstrom
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Antiphase Boundary ◽  
Misfit Dislocations ◽  
Surface Steps ◽  
Transmission Electron ◽  
Different Types ◽  
Significant Factors

ABSTRACTThe formation and structures of misfit dislocations are significant factors in understanding heteroepitaxy of lattice-mismatched materials. In this study, GaAs/Si, CoGa/GaAs and ErAs/GaAs heterojunctions in materials grown by molecular-beam epitaxy have been characterized using transmission electron microscopy. Different types of misfit dislocations have been generated at these interfaces. The different dislocation configurations are discussed, along with interactions between 60° and 90° dislocations in GaAs/Si heterojunctions; the 60° dislocations might be associated with surface steps or edges of islands. The growth of antiphase boundary structures in the CoGa and ErAs grown on GaAs are proposed.

Structures of Nb/Al2O3 Interfaces Produced by Different Experimental Routes

1990 ◽  
Vol 183 ◽  
Author(s):  
J. Mayer ◽  
W. Mader ◽  
D. Knauss ◽  
F. Ernst ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam ◽  
Al Alloy ◽  
Misfit Dislocations ◽  
Orientation Relationships ◽  
Cross Sectional ◽  
Mbe Growth ◽  
Sapphire Substrates ◽  
Transmission Electron

AbstractNb/Al2O3 interfaces were produced by (i) diffusion bonding of single crystalline Nb and Al2O3 at 1973 K, (ii) internal oxidation of a Nb-3at.% Al alloy at 1773 K, and (iii) molecular beam epitaxy (MBE) growth of 500 nm thick Nb overlayers on sapphire substrates at 1123 K. Cross-sectional specimens were prepared and studied by conventional (CTEM) and high resolution transmission electron microscopy (HREM). The orientation relationships between Nb and Al2O3 were identified by diffraction studies. HREM investigations revealed the structures of the different interfaces including the presence of misfit dislocations at or near the interface. The results for the different interfaces are compared.

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