Layer Tilt and Relaxation in InGaAs/GaAs Graded Buffer Layers

1995 ◽  
Vol 379 ◽  
Author(s):  
K.M. Matney ◽  
J.W. Eldredge ◽  
M.S. Goorsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Cross Section ◽  
Mole Fraction ◽  
Molecular Beam ◽  
Reciprocal Space ◽  
Buffer Layers ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTWe investigated the effect of substrate inclination and direction on the structural properties of an InGaAs linearly compositionally graded buffer layer with a AlGaAs/InGaAs superlattice grown by molecular beam epitaxy on 2° offcut GaAs substrates. Reciprocal space maps were used to determine the relaxation and tilt of the buffer layer and superlattice with respect to each other and to the substrate. From (004) reciprocal space maps, a linear relationship between tilt and In mole fraction was observed for the buffer layer. This tilt was greatly reduced near the top of the buffer which was found to be completely strained. Interestingly, the tilt along a <110> direction was greater than that observed along the miscut axis. This may be due to the miscut axis not being parallel to a low index plane. Reciprocal space maps of asymmetric diffraction planes were used to determine the relaxation of the buffer layer as a function of In mole fraction. Along a <110> direction in which no tilt was seen in the (004), the majority of the buffer layer was found to be completely relaxed. However, the top of the buffer layer was found to be completely strained, corresponding to a denuded zone observed in cross section transmission electron microscopy.

Structural Studies Of (ZnSe/FeSe) Superlattices By Transmission Electron Microscopy

1991 ◽  
Vol 238 ◽  
Author(s):  
K. Park ◽  
L. Salamanca-Riba ◽  
B. T. Jonker
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Molecular Beam ◽  
Misfit Strain ◽  
Structural Studies ◽  
Ordered Structure ◽  
Chemical Ordering ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTThe structural properties of (ZnSe/FeSe) superlattices, grown with and without a ZnSe buffer layer on (001) G a As substrates by molecular beam epitaxy, have been studied by transmission electron microscopy. High quality (ZnSe/FeSe) superlattices are obtained when grown on a ZnSe buffer layer on (001) GaAs substrates. In contrast, nominal (ZnSe/FeSe) superlattices grown directly on (001) GaAs substrates without a buffer layer showed evidence for intermixing of the layers in the superlattice indicating that the superlattice is unstable. We observed a disordered structure and an ordered structure in the resulting Zn1−xFexSe solid solution. The ordered structure corresponds to chemical ordering of Zn and Fe atoms along the < 100 > and < 110 > directions. We have studied the effect of misfit strain in the (ZnSe/FeSe) superlattices on the film quality.

Tem Studies of GaAs/AlGaAs Heterostructures Grown on Patterned Substrates

1987 ◽  
Vol 102 ◽  
Author(s):  
D. M. Hwang ◽  
E. Kapon ◽  
M. C. Tamargo ◽  
J. P. Harbison ◽  
R. Bhat ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Chemical Etching ◽  
Molecular Beam ◽  
Patterned Substrates ◽  
Lateral Direction ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Device Applications ◽  
Substrate Surfaces

ABSTRACTEpitaxical growth rates depend strongly on the crystalline orientations of substrate surfaces. Multilayer growth on pre-patterned substrates with various crystal facets exposed results in a large variation of layer thicknesses in the lateral direction. This lateral definition can be used in device applications. Alternating layers of GaAs and AIGaAs were grown by molecular beam epitaxy on (100) GaAs substrates patterned with grooves and ridges along the [01T] and [011] directions by chemical etching. The results were analyzed with transmission electron microscopy using vertical cross-section techniques. Examples of using this method to fabricate ridges with tips of atomic sharpness and quantum-well lasers are presented.

Defects in Mbe-Grown GaAs/ScxEr1–xAs/GaAs Layers

1990 ◽  
Vol 198 ◽  
Author(s):  
Jane G. Zhu ◽  
Chris J. Palmstrdøm ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Growth Stage ◽  
Molecular Beam ◽  
Gaas Layer ◽  
Stacking Fault ◽  
Initial Growth ◽  
Gaas Substrates ◽  
Transmission Electron

ABSTRACTThe microstructure and the structure of defects in GaAs/ScxEr1–xAs/GaAs (x=0 and 0.3) heterostructures grown on (100) GaAs substrates by molecular beam epitaxy have been characterized using transmission electron microscopy. The top GaAs layer forms islands on ScxEr1–xAs at the initial growth stage, and the area covered by GaAs varies with the growth temperature. In addition to regions of epitactic (100) GaAs, regions of {122}- and (111)-oriented GaAs are observed on (100)-oriented ScxEr1–xAs. A high density of stacking-fault pyramids is found in epilayers of GaAs grown on a thin epilayer of ErAs, where the ErAs layers are only one or two monolayers thick. The apex of each stacking-fault pyramid is located at the ScxEr1–xAs/GaAs interface.

Threading Dislocations in InxGabxAs/GaAs System

1991 ◽  
Vol 240 ◽  
Author(s):  
M. Tamura ◽  
A. Hashimoto ◽  
Y. Nakatsugawa
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Cross Section ◽  
Molecular Beam ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Edge Type ◽  
Transmission Electron ◽  
Fixed Film

ABSTRACTThreading dislocation morphologies and characters, as well as their generation conditions in InxGa1−xAs films grown by molecular-beam epitaxy on GaAs (001) substrates have been examined, mainly using cross-section al transmission electron microscopy (XTEM) as a function of x and film thickness. The formation of severe threading dislocations is detected in epilayers ofx≧0.2 at a fixed film thickness of 3 μm and with film thicknesses greater than 2μmat x=0.2. Most of the observed threading dislocations are 60°- and pure-edge type dislocations along the <211> and [001] directions, respectively. The former type dislocations are mainly observed in layers of x≧0.2; the latter predominantly exist in layers of X≧O.3.

Growth of CeO2 thin films deposited on biaxially textured nickel substrates

2003 ◽  
Vol 18 (1) ◽  
pp. 14-26 ◽  
Author(s):  
D. Eyidi ◽  
M. D. Croitoru ◽  
O. Eibl ◽  
R. Nemetschek ◽  
W. Prusseit
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Buffer Layers ◽  
Plan View ◽  
Ni Substrate ◽  
Transmission Electron ◽  
Nickel Substrates

CeO2 films are technologically important as buffer layers for the integration of superconducting YBa2Cu3O7−δ films on {100}-biaxially textured Ni substrates, yielding a Ni–CeO2–YBa2Cu3O7−δ layer sequence. The Ni–CeO2 interface is a metal–oxide interface, and the misfit between substrate and film is about 9%. An epitaxial growth model was suggested for this system in the literature. The investigated films were deposited by a reactive thermal evaporation process at substrate temperatures of 650–670 °C with a thickness of 100 nm after deposition. The CeO2 films were characterized by plan-view and cross-section transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. The CeO2 films had a strong {100} biaxial texture with a roughness of approximately 90 nm. No intermediate layer could be found by cross-section transmission electron microscopy at the Ni–CeO2 interface. The films had columnar grains with diameters of 20–50 nm, much smaller than the grain size of the Ni substrate, which was larger than 1 μm. Small-angle grain boundaries and small amounts of 〈111〉-oriented grains were evidenced in plan-view samples by diffraction patterns. The Moiré fringes technique was applied and was ideally suited to image the small rotations (≤3°) of the small CeO2 grains with respect to the Ni substrate. These small rotations of small grains showed that the growth was nonepitaxial, however, biaxially textured. In the CeO2 film samples, nanovoids 5–10 nm in size were observed and were mostly located close to the film surface. A model for the growth of CeO2 thin films on nickel substrates can be proposed on the basis of our results.

Dislocation reduction with quantum dots in GaN grown on sapphire substrates by molecular beam epitaxy

2002 ◽  
Vol 722 ◽  
Author(s):  
David J. Smith ◽  
Daming Huang ◽  
Michael A Reshchikov ◽  
Feng Yun ◽  
T. King ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Aln Buffer

AbstractWe have investigated a novel approach for improving GaN crystal quality by utilizing a stack of quantum dots (QDs) in GaN grown on sapphire substrates by molecular beam epitaxy. The GaN films were grown on GaN/AlN buffer layers containing multiple QDs and characterized using x-ray diffraction, photoluminescence, atomic force microscopy, and transmission electron microscopy. The density of the dislocations in the films was determined by defect delineation wet chemical etching and atomic force microscopy. It was found that the insertion of a set of multiple GaN QD layers in the buffer layer effectively reduced the density of the dislocations in the epitaxial layers. As compared to a density of ∼1010cm-2in typical GaN films grown on AlN buffer layers, a density of ∼3×107cm-2was demonstrated in GaN films grown with the QD layers. Transmission electron microscopy observations confirmed termination of threading dislocations by the QD layers.

Structural Characterization of Low-Temperature InN Buffer Layer Grown by RF-MBE

2003 ◽  
Vol 798 ◽  
Author(s):  
T. Araki ◽  
Y. Nanishi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Buffer Layer ◽  
Molecular Beam ◽  
Cubic Phase ◽  
Local Fluctuations ◽  
Transmission Electron ◽  
Surface Migration

ABSTRACTThe microstructure of an InN buffer layer grown on (0001) sapphire at low temperature by radio-frequency molecular beam epitaxy (RF-MBE) is characterized by transmission electron microscopy. The low-temperature InN buffer layer is found to contain local inhomogeneous regions of island-like grains surrounded by misoriented InN grains and inclusions of cubic phase. The generation of such anti-phase InN nuclei near the island-like grains is expected to give rise to defects at the interface. It is considered that these anti-phase InN nuclei are formed by local fluctuations of stoichiometry due to inadequate surface migration during the growth of the InN buffer layer, indicating the important of controlling the surface stoichiometry during InN growth.

A Tem study of Epitaxial FE/AG and MN/AG Superlattices

1989 ◽  
Vol 160 ◽  
Author(s):  
S. Nahm ◽  
L. Salamanca — Riba ◽  
B. T. Jonker ◽  
G. A. Prinz
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Buffer Layer ◽  
Seed Layer ◽  
Gaas Substrate ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Strain Modulation ◽  
Film Substrate ◽  
Sharp Interfaces

AbstractWe have studied the epitaxial growth and structural properities of single crystal Fe/Ag and Mn/Ag superlattices grown on (001) GaAs substrates using transmission electron microscopy. A buffer layer of Ag (001) was grown on a 5 monolayer Fe seed layer on the (001) GaAs substrate before the growth of the superlattice to obtain good quality films. For some samples an intermediate buffer layer of ZnSe was used, as well. Both Fe/Ag and Mn/Ag superlattices with a Ag buffer layer show very sharp interfaces. The densities of dislocations in the film and the buffer layer are the same suggesting that the dislocations originate at the film/substrate interface. We have observed evidence for a strain modulation of ≈ 8 Å in the Mn layer for thick (≈ 22 Å) Mn layers in the superlattice samples but not in samples with a thin Mn layer.

Microstructure of laser-irradiated, conducting Kapton polyimide

1995 ◽  
Vol 53 ◽  
pp. 502-503
Author(s):  
D. L. Callahan ◽  
Z. Ball ◽  
H. M. Phillips ◽  
R. Sauerbrey
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Cross Sectional ◽  
General Utility ◽  
Transmission Electron ◽  
Considerable Debate ◽  
Potential Applications

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.

The use of an energy-filtering electron microscope to reduce chromatic aberration in images of thick biological specimens

1986 ◽  
Vol 44 ◽  
pp. 88-91
Author(s):  
L. D. Peachey ◽  
J. P. Heath ◽  
G. Lamprecht
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Cross Section ◽  
Electron Scattering ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Incident Electron Energy ◽  
Energy Filtering ◽  
Transmission Electron

Biological specimens of cells and tissues generally are considerably thicker than ideal for high resolution transmission electron microscopy. Actual image resolution achieved is limited by chromatic aberration in the image forming electron lenses combined with significant energy loss in the electron beam due to inelastic scattering in the specimen. Increased accelerating voltages (HVEM, IVEM) have been used to reduce the adverse effects of chromatic aberration by decreasing the electron scattering cross-section of the elements in the specimen and by increasing the incident electron energy.

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