On the atomic structure of the Nb/Al2O3 interface and the growth of Al2O3 particles

1989 ◽  
Vol 4 (4) ◽  
pp. 972-977 ◽  
Author(s):  
M. Kuwabara ◽  
J. C. H. Spence ◽  
M. Ruhle
Keyword(s):  
Internal Oxidation ◽  
Growth Mechanism ◽  
Atomic Structure ◽  
Standoff Distance ◽  
Recent Theory ◽  
Misfit Dislocations ◽  
Final Layer ◽  
Metal Ceramic ◽  
Atomically Flat ◽  
Good Agreement

The growth mechanism for small precipitates of Al2O3 formed by internal oxidation in the Nb–Al2O3 interface is studied in detail. The observations show that the Nb (001)/Al2O3 (00.1) interface is almost atomically flat and that there are no interface compounds. We suggest that the final layer on the Al2O3 side of this interface consists of oxygen atoms. The effects of image forces on misfit dislocations are found to result in a standoff distance between dislocation cores and the interface, in good agreement with the recent theory. The implications of this for the strength of metal-ceramic bonding are discussed.

Atomic structure of misfit dislocations in metal‐ceramic interfaces

1995 ◽  
Vol 71 (6) ◽  
pp. 1219-1239 ◽  
Author(s):  
V. Vitek ◽  
G. Gutekunst ◽  
J. Mayer ◽  
M. Rühle
Keyword(s):  
Atomic Structure ◽  
Misfit Dislocations ◽  
Metal Ceramic ◽  
Ceramic Interfaces

Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

1992 ◽  
Vol 50 (1) ◽  
pp. 106-107
Author(s):  
H.W. Zandbergen ◽  
M.R. McCartney
Keyword(s):  
Electron Microscopy ◽  
Copper Oxide ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Oxygen Deficiency ◽  
Surface Layers ◽  
Layer Sequence ◽  
Surface Reconstructions ◽  
Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

Atomic structure of stair rod misfit dislocations at the GaAs on Si(100) interface

1990 ◽  
Vol 48 (4) ◽  
pp. 342-343
Author(s):  
D. Gerthsen
Keyword(s):  
Lattice Constant ◽  
Atomic Structure ◽  
Spherical Aberration ◽  
Stacking Faults ◽  
Misfit Dislocations ◽  
Gaas On Si ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Intersection Line ◽  
Oriented Parallel

The prospect of technical applications has induced a lot of interest in the atomic structure of the GaAs on Si(100) interface and the defects in its vicinity which are often studied by high resolution transmission electron microscopy. The interface structure is determined by the 4.1% lattice constant mismatch between GaAs and Si, the large difference between the thermal expansion coefficients and the polar/nonpolar nature of the GaAs on Si interface. The lattice constant mismatch is compensated by misfit dislocations which are characterized by a/2<110> Burgers vectors b which are oriented parallel or inclined on {111} planes with respect to the interface. Stacking faults are also frequently observed. They are terminated by partial dislocations with b = a/6<112> on {111} planes. In this report, the atomic structure of stair rod misfit dislocations is analysed which are located at the intersection line of two stacking faults at the interface.A very thin, discontinous film of GaAs has been grown by MBE on a Si(100) substrate. Fig.1.a. shows an interface section of a 27 nm wide GaAs island along [110] containing a stair rod dislocation. The image has been taken with a JEOL 2000EX with a spherical aberration constant Cs = 1 mm, a spread of focus Δz = 10 nm and an angle of beam convergence ϑ of 2 mrad.

Quasiperiodic interfaces: HREM observations of grain and phase boundaries

1990 ◽  
Vol 48 (4) ◽  
pp. 332-333
Author(s):  
K. L. Merkle
Keyword(s):  
Atomic Structure ◽  
Direct Determination ◽  
Lattice Parameter ◽  
Atomic Scale ◽  
Misfit Dislocations ◽  
Oxide Systems ◽  
Atomic Structures ◽  
Periodic Arrays ◽  
Parameter Ratio ◽  
Metal Metal

The atomic structures of internal interfaces have recently received considerable attention, not only because of their importance in determining many materials properties, but also because the atomic structure of many interfaces has become accessible to direct atomic-scale observation by modem HREM instruments. In this communication, several interface structures are examined by HREM in terms of their structural periodicities along the interface.It is well known that heterophase boundaries are generally formed by two low-index planes. Often, as is the case in many fcc metal/metal and metal/metal-oxide systems, low energy boundaries form in the cube-on-cube orientation on (111). Since the lattice parameter ratio between the two materials generally is not a rational number, such boundaries are incommensurate. Therefore, even though periodic arrays of misfit dislocations have been observed by TEM techniques for numerous heterophase systems, such interfaces are quasiperiodic on an atomic scale. Interfaces with misfit dislocations are semicoherent, where atomically well-matched regions alternate with regions of misfit. When the misfit is large, misfit localization is often difficult to detect, and direct determination of the atomic structure of the interface from HREM alone, may not be possible.

Atomic structure of misfit dislocations in nonpolar ZnO/Al2O3 heterostructures

2010 ◽  
Vol 97 (12) ◽  
pp. 121914 ◽  
Author(s):  
H. Zhou ◽  
M. F. Chisholm ◽  
P. Pant ◽  
H. J. Chang ◽  
J. Gazquez ◽  
...  
Keyword(s):  
Atomic Structure ◽  
Misfit Dislocations

scholarly journals Observation of surface wave patterns modified by sub-surface shear currents

2019 ◽  
Vol 873 ◽  
pp. 508-530 ◽  
Author(s):  
Benjamin K. Smeltzer ◽  
Eirik Æsøy ◽  
Simen Å. Ellingsen
Keyword(s):  
Surface Wave ◽  
Empirical Support ◽  
Surface Flow ◽  
Recent Theory ◽  
Transient Effects ◽  
Surface Shear ◽  
Ship Waves ◽  
Shear Current ◽  
Wave Patterns ◽  
Good Agreement

We report experimental observations of two canonical surface wave patterns – ship waves and ring waves – skewed by sub-surface shear, thus confirming effects predicted by recent theory. Observed ring waves on a still surface with sub-surface shear current are strikingly asymmetric, an effect of strongly anisotropic wave dispersion. Ship waves for motion across a sub-surface current on a still surface exhibit striking asymmetry about the ship’s line of motion, and large differences in transverse wavelength for upstream versus downstream motion are demonstrated, all of which is in good agreement with theoretical predictions. Neither of these phenomena can occur on a depth-uniform current. A quantitative comparison of measured versus predicted average phase shift for a ring wave is grossly mispredicted by no-shear theory, but in good agreement with predictions for the measured shear current. A clear difference in wave frequency within the ring wave packet is observed in the upstream versus downstream direction for all shear flows, while wave dispersive behaviour is identical to that for quiescent water for propagation normal to the shear current, as expected. Peak values of the measured two-dimensional Fourier spectrum for ship waves are shown to agree well with the predicted criterion of stationary ship waves, with the exception of some cases where results are imperfect due to the limited wavenumber resolution, transient effects and/or experimental noise. Experiments were performed on controlled shear currents created in two different ways, with a curved mesh and beneath a blocked stagnant-surface flow. Velocity profiles were measured with particle image velocimetry, and surface waves with a synthetic schlieren method. Our observations lend strong empirical support to recent predictions that wave forces on vessels and structures can be greatly affected by shear in estuarine and tidal waters.

Effect of C and Ge Concentration On The Thermal Stability of RTCVD Grown Si1-x-yGexCy Alloys

1997 ◽  
Vol 470 ◽  
Author(s):  
Patricia Warren ◽  
Stephane Retzmanick ◽  
Martin Gotza ◽  
Marc Begems
Keyword(s):  
Lattice Constant ◽  
Strain Relaxation ◽  
Mechanical Strain ◽  
Chemical Vapor ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
Cubic Silicon Carbide ◽  
Kinetics Of ◽  
Good Agreement

ABSTRACTSi / Si1-x-yGexCy / Si heterostructures containing up to 17 at.% Ge and 1.9 at.% C were grown on (001) silicon by low pressure Rapid Thermal Chemical Vapor Deposition, using a mixture of silane, germane and methylsilane, diluted in hydrogen. The samples were then annealed in a Rapid Thermal Processing furnace, under an atmospheric pressure of nitrogen, at temperatures ranging from 900 to 1130 °C.The samples were characterized using infrared spectroscopy and x-ray diffraction. SIMS profiling and TEM observation were performed on some of the samples.Substitutional C gradually disappeared, either precipitating out to form cubic silicon carbide (β-SiC), or simply vanishing into interstitial positions. In any case, the in-plane lattice constant remained constant after annealing, indicating that there was no mechanical strain relaxation by formation of misfit dislocations. The perpendicular lattice constant increased due to the decrease in substitutional C concentration, as well as it decreased due to the germanium out-diffusion. This variation of the strain during annealing was modeled, and allowed the determination of the kinetics of the substitutional carbon disappearance. The same behavior was observed for all samples. Indeed, the Cs disappearance rate was always increased for samples with higher initial Ge and C concentrations. The kinetics of this precipitation was found in very good agreement with previous published results.

Misfit dislocations at metal-ceramic interfaces

1995 ◽  
Vol 149 (1) ◽  
pp. 95-103 ◽  
Author(s):  
W. P. Vellinga ◽  
J. Th. M. De Hosson
Keyword(s):  
Misfit Dislocations ◽  
Metal Ceramic ◽  
Ceramic Interfaces

Micro-Computed Tomography Image Based Numerical Elastic Homogenization of MMCs

2014 ◽  
Vol 627 ◽  
pp. 437-440 ◽  
Author(s):  
Yuriy Sinchuk ◽  
Stefan Dietrich ◽  
Matthias Merzkirch ◽  
Kay André Weidenmann ◽  
Romana Piat
Keyword(s):  
Computed Tomography ◽  
Elastic Properties ◽  
Ceramic Composite ◽  
Finite Element Models ◽  
Micro Computed Tomography ◽  
Tomography Image ◽  
Metal Ceramic ◽  
Computed Tomography Image ◽  
2D And 3D ◽  
Good Agreement

Properties of an interpenetrating metal–ceramic composite with freeze-cast preforms are investigated. For the estimation of elastic properties of the composite numerical homogenization approaches for 2D and 3D finite element models are implemented. The FE models are created based on micro-computed tomography (μCT) images. The results of the numerical 2D and 3D modeling coincide and are in good agreement with available experimental measurements of elastic properties.

The oval defects on MBE grown GaAs(100)

1990 ◽  
Vol 48 (4) ◽  
pp. 720-721
Author(s):  
Tung Hsu ◽  
G.S. Petrich ◽  
P. I. Cohen
Keyword(s):  
Electron Microscope ◽  
Computer Model ◽  
Flux Ratio ◽  
Specimen Surface ◽  
General Shape ◽  
Atomic Steps ◽  
Stages Of Growth ◽  
Atomically Flat ◽  
Good Agreement

Oval defects were observed on specimens of MBE grown GaAs(100) samples. Substrates were GaAs(100) tilted 2ò toward [011] (A misorientation); chemically etched before growing 0.2μm of GaAs at 600òC, at a rate of 0.4μm/h, and using a 3:1 As:Ga flux ratio. After the growth samples were transferred through air to a JEOL-200CX electron microscope for REM and RHEED study,Surfaces of the sample exhibited bunched atomic steps and wide atomically flat (100) terraces. There were approximately 100 such defects, large and small, within a specimen surface of 1 mm2.The defects were of various sizes, indicating that they were at different stages of growth, but had the same general shape. After shooting a series of pictures from different azimuth angles, a three demensional computer model is then constructed and the model is tilted and rotated to simulated the views from different directions. There is a good agreement between the simulated and the experimental pictures.

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