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.

scholarly journals Structural Property Study for GeSn Thin Films

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3645
Author(s):  
Liyao Zhang ◽  
Yuxin Song ◽  
Nils von den Driesch ◽  
Zhenpu Zhang ◽  
Dan Buca ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Transmission Electron

The structural properties of GeSn thin films with different Sn concentrations and thicknesses grown on Ge (001) by molecular beam epitaxy (MBE) and on Ge-buffered Si (001) wafers by chemical vapor deposition (CVD) were analyzed through high resolution X-ray diffraction and cross-sectional transmission electron microscopy. Two-dimensional reciprocal space maps around the asymmetric (224) reflection were collected by X-ray diffraction for both the whole structures and the GeSn epilayers. The broadenings of the features of the GeSn epilayers with different relaxations in the ω direction, along the ω-2θ direction and parallel to the surface were investigated. The dislocations were identified by transmission electron microscopy. Threading dislocations were found in MBE grown GeSn layers, but not in the CVD grown ones. The point defects and dislocations were two possible reasons for the poor optical properties in the GeSn alloys grown by MBE.

Cantilever Epitaxy of GaN on Sapphire: Further Reductions in Dislocation Density

2002 ◽  
Vol 743 ◽  
Author(s):  
D. M. Follstaedt ◽  
P. P. Provencio ◽  
D. D. Koleske ◽  
C. C. Mitchell ◽  
A. A. Allerman ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Processing Conditions ◽  
Optimum Growth ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Threading Dislocation Density

ABSTRACTThe density of vertical threading dislocations at the surface of GaN grown on sapphire by cantilever epitaxy has been reduced with two new approaches. First, narrow mesas (<1 μm wide) were used and {11–22} facets formed over them early in growth to redirect dislocations from vertical to horizontal. Cross-sectional transmission electron microscopy was used to demonstrate this redirection and to identify optimum growth and processing conditions. Second, a GaN nuc-leation layer with delayed 3D → 2D growth transition and inherently lower threading dislocation density was adapted to cantilever epitaxy. Several techniques show that a dislocation density of only 2–3×107/cm2 was achieved by combining these two approaches. We also suggest other developments of cantilever epitaxy for reducing dislocations in heteroepitaxial systems.

Growth of Metamorphic InGaP for Wide-Bandgap Photovoltaic Junction by MBE

2010 ◽  
Vol 1268 ◽  
Author(s):  
John Simon ◽  
Stephanie Tomasulo ◽  
Paul Simmonds ◽  
Manuel J Romero ◽  
Minjoo Larry Lee
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam ◽  
Strain Relaxation ◽  
Wide Bandgap ◽  
Threading Dislocation ◽  
Step Size ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Substrate Temperatures

AbstractMetamorphic triple-junction solar cells can currently attain efficiencies as high as 41.1%. Using additional junctions could lead to efficiencies above 50%, but require the development of a wide bandgap (2.0-2.2eV) material to act as the top layer. In this work we demonstrate wide bandgap InyGa1-yP grown on GaAsxP1-x via solid source molecular beam epitaxy. Unoptimized tensile GaAsxP1-x buffers grown on GaAs exhibit asymmetric strain relaxation, along with formation of faceted trenches 100-300 nm deep in the [01-1] direction. Smaller grading step size and higher substrate temperatures minimizes the facet trench density and results in symmetric strain relaxation. In comparison, compressively-strained graded GaAsxP1-x buffers on GaP show nearly-complete strain relaxation of the top layers and no evidence of trenches. We subsequently grew InyGa1-yP layers on the GaAsxP1-x buffers. Photoluminescence and transmission electron microscopy measurements show no indication of phase separation or CuPt ordering. Taken in combination with the low threading dislocation densities obtained, MBE-grown InyGa1-yP layers are promising candidates for future use as the top junction of a multi-junction solar cell.

Dependence of the Defects Present in InAlAs/InP on the Substrate Temperature

1991 ◽  
Vol 240 ◽  
Author(s):  
F. Peiro ◽  
A. Cornet ◽  
A. Herms ◽  
J. R. Morante ◽  
A. Georgakilas ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Substrate Temperature ◽  
Molecular Beam ◽  
Stacking Faults ◽  
Structural Defects ◽  
Threading Dislocations ◽  
Transmission Electron ◽  
Inp Substrates

ABSTRACTThe crystalline quality of InAlAs layers, grown by Molecular Beam Epitaxy on (100) InP substrates, has been investigated by Transmission Electron Microscopy in order to study the influence of InAlAs growth temperature (Tg) on the density of structural defects present in the layers. Tg was varied from 300°C up to 530°C. The density of stacking faults and threading dislocations drops dramatically as Tg increas

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.

Surface Films on Zircaloy-2 Samples Cracked in Neutral Aqueous NaCl by Stress Corrosion

1973 ◽  
Vol 31 ◽  
pp. 46-47
Author(s):  
R.A. Ploc
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Stress Corrosion ◽  
Zirconium Dioxide ◽  
Surface Film ◽  
Surface Films ◽  
Continuous Layer ◽  
Transmission Electron ◽  
Product Film

Samples of low-nickel Zircaloy-2 (material MLI-788-see(1)), when anodically polarized in neutral 5 wt% NaCl solutions, were found to be susceptible to pitting and stress corrosion cracking. The SEM revealed that pitting of stressed samples was occurring below a 2000Å thick surface film which behaved differently from normal zirconium dioxide in that it did not display interference colours. Since the initial film thickness was approximately 65Å, attempts were made to examine the product film by transmission electron microscopy to deduce composition and how the corrosion environment could penetrate the continuous 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.

Vertical self-organization of Ge1−xMnx nanocolumn multilayers grown on Ge(001) substrates

2016 ◽  
Vol 30 (20) ◽  
pp. 1650269 ◽  
Author(s):  
Thi Giang Le ◽  
Minh Tuan Dau
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam Epitaxy ◽  
Elastic Constant ◽  
Structural Properties ◽  
Molecular Beam ◽  
Self Organization ◽  
Transmission Electron ◽  
2D Model

High-resolution transmission electron microscopy (HR-TEM) has been used to investigate the structural properties of GeMn/Ge nanocolumns multilayer samples grown on Ge(001) substrates by means of molecular beam epitaxy (MBE) system. Four bilayers with the spacer thickness in the range between 6 nm and 15 nm and 10 periods of bilayers of Ge[Formula: see text]Mn[Formula: see text]/Ge nanocolumn are presented. A simplified 2D model based on the theory of elastic constant interactions has been used to provide reasonable explanations to the vertical self-organization of GeMn nanocolumns in multilayers.

TEM Characterization of As-Deposited and Annealed Ni/Al Multilayer Thin Film

2010 ◽  
Vol 16 (6) ◽  
pp. 662-669 ◽  
Author(s):  
S. Simões ◽  
F. Viana ◽  
A.S. Ramos ◽  
M.T. Vieira ◽  
M.F. Vieira
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Ion Beam ◽  
Microstructural Characterization ◽  
Multilayer Thin Films ◽  
Tem Analysis ◽  
Plan View ◽  
Transmission Electron

AbstractReactive multilayer thin films that undergo highly exothermic reactions are attractive choices for applications in ignition, propulsion, and joining systems. Ni/Al reactive multilayer thin films were deposited by dc magnetron sputtering with a period of 14 nm. The microstructure of the as-deposited and heat-treated Ni/Al multilayers was studied by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) in plan view and in cross section. The cross-section samples for TEM and STEM were prepared by focused ion beam lift-out technique. TEM analysis indicates that the as-deposited samples were composed of Ni and Al. High-resolution TEM images reveal the presence of NiAl in small localized regions. Microstructural characterization shows that heat treating at 450 and 700°C transforms the Ni/Al multilayered structure into equiaxed NiAl fine grains.

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