The Structure of Spinel/Oxide Reaction Fronts During Spinel-Forming Solid State Reactions

1994 ◽  
Vol 357 ◽  
Author(s):  
D. Hesse ◽  
R. Scholz ◽  
S. Senz ◽  
H. Sieber ◽  
P. Werner ◽  
...  
Keyword(s):  
Solid State ◽  
Reaction Front ◽  
Lattice Misfit ◽  
Solid State Reactions ◽  
Interface Plane ◽  
Misfit Dislocations ◽  
Spinel Oxide ◽  
Oxygen Sublattice ◽  
Cross Sectional ◽  
Reaction Fronts

AbstractA series of spinels were grown by topotaxial solid state reaction on MgO(001) and sapphire(11.2) substrates. The structure of the various spinel/oxide reaction fronts was investigated by cross-sectional high resolution electron microscopy and other methods. While for extremely low misfit the reaction front is completely coherent, different interfacial defects form in other cases, depending on sign and amount of the spinel/oxide lattice misfit. For a large positive misfit, a network of misfit dislocations occured all running along <100<, with Burgers vectors of types a/2[101] and a/2[011] pointing out of the interface. The perpendicular Burgers vector component along [001] permits these dislocations to glide in order to cope with the advancing reaction front, avoiding kinetically unfavourable climb processes. The latter have, however, been observed in negative misfit, where the interfacial dislocations run along <110>, with their Burgers vectors lying in the interface plane. At the sapphire/MgAl2O4 front the structure is completely different. Here the h.c.p.-type oxygen sublattice of sapphire is reconstructed into the f.c.c-type oxygen sublattice of the spinel, which requires a tilt of the MgAl2O4 lattice and the formation of interfacial ledges.

The wustite-spinel interface

1987 ◽  
Vol 45 ◽  
pp. 268-269
Author(s):  
S.R. Summerfelt ◽  
C.B. Carter
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Strain Energy ◽  
Matrix Material ◽  
Lattice Misfit ◽  
Solid State Reactions ◽  
Oxygen Sublattice ◽  
Large Particles ◽  
Small Lattice ◽  
Coherent Interfaces

The wustite-spinel interface can be viewed as a model interface because the wustite and spinel can share a common f.c.c. oxygen sublattice such that only the cations distribution changes on crossing the interface. In this study, the interface has been formed by a solid state reaction involving either external or internal oxidation. In systems with very small lattice misfit, very large particles (>lμm) with coherent interfaces have been observed. Previously, the wustite-spinel interface had been observed to facet on {111} planes for MgFe2C4 and along {100} planes for MgAl2C4 and MgCr2O4, the spinel then grows preferentially in the <001> direction. Reasons for these experimental observations have been discussed by Henriksen and Kingery by considering the strain energy. The point-defect chemistry of such solid state reactions has been examined by Schmalzried. Although MgO has been the principal matrix material examined, others such as NiO have also been studied.

Time-Dependent Interfacial Reaction Mechanism in a Spinel-Forming Solid State Reaction Studied by TEM

1996 ◽  
Vol 466 ◽  
Author(s):  
P. Werner ◽  
H. Sieber ◽  
R. Huxebrand ◽  
D. Hesse
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Interfacial Reaction ◽  
Lattice Misfit ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Time Dependent ◽  
Solid State Reactions ◽  
Misfit Dislocations ◽  
Resolution Electron

ABSTRACTInterfacial reaction mechanisms were investigated in case of topotaxial formation of MgIn2O4 spinel on MgO crystals, which is an appropriate model system for thin film solid state reactions in ceramics. The reaction interface MgO/MgIn2O4(001), which is characterized by a large lattice misfit (+4.2%) between these cubic crystals, was investigated by transmission electron microscopy (TEM). Thin spinel films (thickness t< 0.5μm) consist of domains tilted off (≈3.5°) the exact cube-to-cube orientation into four directions, while thicker films (t> 1μm) show an accurate (001) orientation. High-resolution electron microscopy (HREM) showed that this time-dependent orientation behavior correlates with the atomic scale structure of the interface, especially with the different types of misfit dislocations. Based on these results, the misfit accommodation mechanism at the propagating reaction front in this spinel system is discussed including transitions between glide and climb processes.

Solid state reactions between Ni3Al and SiC

1990 ◽  
Vol 5 (9) ◽  
pp. 1985-1994 ◽  
Author(s):  
T. C. Chou ◽  
T. G. Nieh
Keyword(s):  
Growth Rate ◽  
Solid State ◽  
Solid State Reactions ◽  
Growth Rate Constant ◽  
Cross Sectional ◽  
Rate Limiting Step ◽  
Nial Phase ◽  
Reaction Zones ◽  
Carbon Precipitation ◽  
Terminal Component

Solid state reactions between SiC and Ni3Al were studied at 1000°C for different times. Multi-reaction-layers were generated in the interdiffusion zone. Cross-sectional views of the reaction zones show the presence of three distinguishable layers. The Ni3Al terminal component is followed by NiAl, Ni5.4Al1Si2, Ni(5.4−x)Al1Si2 + C layers, and the SiC terminal component. The Ni5.4Al1Si2 layer shows carbon precipitation free, while modulated carbon bands were formed in the Ni(5.4−x)Al1Si2 + C layer. The NiAl layer shows dramatic contrast difference with respect to the Ni3Al and Ni5.4Al1Si2 layers, and is bounded by the Ni3Al/NiAl and Ni5.4Al1Si2/NiAl phase boundaries. The kinetics of the NiAl formation is limited by diffusion, and the growth rate constant is measured to be 2 ⊠ 10−10 cm2/s. The thickness of the reaction zone on the SiC side is always thinner than that on the Ni3Al side and no parabolic growth rate is obeyed, suggesting that the decomposition of the SiC may be a rate limiting step for the SiC/Ni3Al reactions. The carbon precipitates were found to exist in either a disordered or partially ordered (graphitic) state, depending upon their locations from the SiC interface. The formation of NiAl phase is discussed based on an Al-rejection model, as a result of a prior formation of Ni–Al–Si ternary phase. A thermodynamic driving force for the SiC/Ni3Al reactions is suggested.

Transmission Electron Microscopy Study of Epitaxial Co/Au and Co/Pd (111) Multilayers

1992 ◽  
Vol 263 ◽  
Author(s):  
A.E.M. de Veirman ◽  
F. Hakkens ◽  
W. Coene ◽  
F.J.A. Den Broeder
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Interface Plane ◽  
Misfit Dislocations ◽  
Transmission Electron Microscopy Study ◽  
Cross Sectional ◽  
Transmission Electron

ABSTRACTThe results of a transmission electron microscopy study of Co/Au and Co/Pd multilayers are reported. Special emphasis is put on the epitaxial growth and the relaxation of the misfit strain of these high misfit systems. In bright-field cross-sectional images, periodic contrast fringes are observed at the interfaces, which are the result of Moiré interference and which allow determination of the degree of misfit relaxation at the interface. It was established that 80-85% of the misfit is relaxed. From high resolution electron microscopy images the Burgers vector of the misfit dislocations was derived, being a/2<110> lying in the (111) interface plane. The results obtained for the Co/Au and Co/Pd multilayers will be discussed in comparison with those obtained for a bilayer of Co and Au.

Strain Relaxation in GaAs on Si by Two Groups of Misfit Dislocations

1995 ◽  
Vol 399 ◽  
Author(s):  
M. Tamura ◽  
T. Saitoh ◽  
T. Yodo
Keyword(s):  
Strain Relaxation ◽  
Lattice Misfit ◽  
Misfit Dislocations ◽  
Cross Sectional ◽  
Plan View ◽  
Partial Dislocations ◽  
Group I ◽  
Transmission Electron ◽  
Before And After ◽  
Gaas Films

ABSTRACTHigh-resolution cross-sectional and conventional plan-view transmission electron microscope observations have been carried out for molecular beam epitaxially grown GaAs films on vicinal Si (001) as a function of film thicknesses and observation directions between two orthogonal <110> directions before and after annealing. Two groups of misfit dislocations are characterized by analyzing whether their extra half planes exist in the film and the substrate side. The group I misfit dislocations due to a stress caused by a lattice misfit between GaAs and Si consist of partial and, 60° and 90° complete dislocations in an as-grown state. After annealing partial dislocations almost disappear and 90° perfect dislocations are predominantly observed. The group II misfit dislocations due to a thermal-expansion misfit-induced stress are all of the 60° type complete dislocations, independent of film thickness and annealing.

Non-Alloyed Ohmic Contacts to n-GaAs Using Epitaxial Ge Layers

1985 ◽  
Vol 54 ◽  
Author(s):  
T. Sawada ◽  
W. X. Chen ◽  
E. D. Marshall ◽  
K. L. Kavanagh ◽  
T. F. Kuech ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Solid State ◽  
Ohmic Contacts ◽  
Solid Phase ◽  
Solid State Reactions ◽  
Solid Phase Epitaxy ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Shallow Junctions

ABSTRACTAlloyed ohmic contacts (i.e. Au-Ge-Ni) to n-GaAs lead to non-planar interfaces which are unsuitable for devices with shallow junctions and small dimensions. In this study, the fabrication of non-alloyed ohmic contacts (via solid state reactions) is investigated. A layered structure involving the solid phase epitaxy of Ge using a transport medium (PdGe) is shown to produce low (1 — 5 × 10∼6Ω cm2) and reproducible values of contact resistivity. The resultant interface is shown to be abrupt by cross-sectional transmission electron microscopy.

The Spinel/Alumina Phase Boundary

1985 ◽  
Vol 43 ◽  
pp. 216-217 ◽  
Author(s):  
Y.M. Kouh ◽  
C.B. Carter ◽  
H. Schmalzried
Keyword(s):  
Solid State ◽  
Phase Boundary ◽  
Solid State Reactions ◽  
Oxygen Sublattice ◽  
Oxygen Ions ◽  
Shockley Partial ◽  
Alumina Phase ◽  
Small Rotation ◽  
Structural Aspects

The formation of spinel during solid-state reactions between two oxides of the type A0 (e.g. Mg0) and B203 (e.g. A1203), has been extensively studied both from a theoretical viewpoint and an experimental one. The present paper will illustrate the structural aspects of the study of the spinel/sesquioxide interface. It has recently been shown by Carter and Schmalzried, that, when Co0 and A1203 react to form Co-Al spinel, the {111} oxygen planes in the spinel do not lie parallel to the (0001) oxygen planes in the parent alumina even though the oxygen ions are almost close-packed in both planes. The small rotation which is present implies that the mechanism whereby the alumina is transformed to spinel is not simply the glide of either isolated, or bundles of, Shockley partial-like transformation dislocations as had previously been assumed, but rather involves a new defect which causes a rotation of the oxygen sublattice.

CaP/Si Heteroepitaxial Layers with Reduced Defect Density

1988 ◽  
Vol 116 ◽  
Author(s):  
A.E. Blakeslee ◽  
M.M. Al—jassim ◽  
J.M. Olson ◽  
K.M. Jones ◽  
S.M. Vernon
Keyword(s):  
Defect Density ◽  
Three Dimensional ◽  
Interface Plane ◽  
Misfit Dislocations ◽  
Cross Sectional ◽  
Single Temperature ◽  
Planar Network ◽  
Reduced Density ◽  
Oxide Contamination ◽  
Threading Defects

AbstractIt is shown that GaP layers grown upon Si at a single temperature of 900ºC can have a crystalline quality superior to that exhibited by previous two—step and one—step growth methods. The layers are characterized by a planar network of misfit dislocations confined to the interface plane an a reduced density of threading dislocations (low 106 cm-2; previously >108). Very few threading defects were observed in areas devoid of amorphous oxide contamination, as shown by HREM examination of cross—sectional samples. A low growth rate during nucleation enhances crystalline perfection, since it decreases the tendency toward three—dimensional islanding.

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