Oriented growth of sillimanite in andalusite, Placitas – Juan Tabo area, New Mexico, U.S.A.

1987 ◽  
Vol 24 (3) ◽  
pp. 580-590 ◽  
Author(s):  
R. H. Vernon
Keyword(s):  
New Mexico ◽  
Regional Metamorphism ◽  
Stacking Faults ◽  
Local Scale ◽  
Strain Accumulation ◽  
Oriented Growth ◽  
Screw Dislocations ◽  
Time Path ◽  
Granite Emplacement ◽  
Nucleation Sites

In metapelitic schists near the Sandia granite in the Placitas – Juan Tabo area, New Mexico, nucleation sites for sillimanite are very variable, but growth of sillimanite in andalusite is common, either as bundles of fibrous ("fibrolitic") sillimanite crystals or as coarser grained parallel prisms or dendritic crystals of sillimanite. Optical relationships indicate a coaxial relationship between the andalusite and the sillimanite but with a and b axes interchanged. Stacking faults formed by dissociated screw dislocations in the andalusite may have provided nucleation sites for sillimanite. Some large sillimanite grains appear to have formed by coarsening of fibrous sillimanite, but others show no evidence of such coarsening. Some fibrous sillimanite occurs in folia in zones of inferred noncoaxial strain accumulation. Some occurs in radiating or crystallographically controlled aggregates in low-strain zones between sillimanite folia. These aggregates do not necessarily indicate postdeformation growth, except on a very local scale, and many of the fibrous sillimanite aggregates have been deformed. Hence, the sillimanite is a product of syndeformational rather than post-deformational metamorphism, as previously suggested, although regional metamorphism and granite emplacement may have been broadly synchronous. The andalusite–sillimanite microstructural relationships indicate a prograde P–T–time path similar to those occurring in other low-pressure (andalusite–sillimanite) metamorphic areas.

The atomic structure of growth interfaces in Y–Ba–Cu–O thin films

1991 ◽  
Vol 6 (11) ◽  
pp. 2264-2271 ◽  
Author(s):  
R. Ramesh ◽  
A. Inam ◽  
D.M. Hwang ◽  
T.S. Ravi ◽  
T. Sands ◽  
...  
Keyword(s):  
Thin Films ◽  
Atomic Structure ◽  
Film Growth ◽  
Substrate Surface ◽  
Oriented Growth ◽  
Surface Steps ◽  
Nucleation Sites ◽  
Oriented Films ◽  
Second Phases ◽  
Ledge Mechanism

We have examined the atomic structure of growth interfaces in thin films of Y–Ba–Cu–O grown on [001] perovskite or cubic substrates. At substrate heater temperatures in the range of 780–820 °C c-axis oriented growth is observed on these substrates. On SrTiO3, the first layer appears to be either a BaO or a CuO2 plane while on LaAlO3 the first layer appears to be a CuO chain layer. The mismatch on the a-b plane is accommodated by the formation of interface dislocations. Defects on the substrate surface propagate as defects in the film. These defects are primarily translational boundaries and in some cases second phases. At lower substrate heater temperatures, i.e., 650–700 °C, a, b-axis growth dominates. Defects and steps on the substrate surface are more detrimental in the growth of a, b-axis oriented films, since they tend to favor the nucleation of c-axis oriented domains. This is ascribed to the ledge mechanism of c-axis film growth, for which the surface steps are good nucleation sites.

Dislocations Propagation Study Trough High-Resolution 4H-SiC Substrate Mapping

2019 ◽  
Vol 963 ◽  
pp. 276-279 ◽  
Author(s):  
Ruggero Anzalone ◽  
Nicolò Piluso ◽  
Andrea Severino ◽  
Simona Lorenti ◽  
Giuseppe Arena ◽  
...  
Keyword(s):  
High Resolution ◽  
Epitaxial Layer ◽  
Basal Plane ◽  
Stacking Faults ◽  
Screw Dislocations ◽  
Density Maps ◽  
Dislocations Density ◽  
Koh Etching

In this work a deep investigation of the dislocation on 4H-SiC substrate has been shown. The dislocation intersecting the surface were enhanced by KOH etching at 500 deg. C. performed on whole 6 inches substrate. A comparison between basal plane dislocations and threading screw dislocations in the substrate with the defects in the epitaxial layer (mainly stacking faults and carrots) was performed. The comparison between shows a correlation between basal plane dislocations density and stacking faults density maps.

Nucleation & Growth of Defects in SOI Materials

1995 ◽  
Vol 378 ◽  
Author(s):  
G. C. M. Silvestre ◽  
R. A. Moore ◽  
B. J. Kennedy
Keyword(s):  
Stacking Faults ◽  
Silicon On Insulator ◽  
Device Performance ◽  
Low Doses ◽  
Bulk Silicon ◽  
Counting System ◽  
Partial Dislocations ◽  
Nucleation Sites ◽  
Oxygen Precipitates ◽  
Interface Effects

AbstractTo produce Silicon-On-Insulator (SOI) materials with thin Si overlayer, sacrificial oxidation is often used. This creates defects which have adverse effects on device performance. It has been observed that Stacking Faults (SFs) in thin Separation-by-IMplantation-of-OXygen (SIMOX) or Bonded-and-Etched-back-SOI (BESOI) films of less than 600 Å, do not shrink as expected during neutral Ar anneals. Shrinkage of SFs in standard bulk substrates with different capping layers has been investigated to promote the understanding of the Si/Si02 interface effects on Si interstitial incorporation during anneals. The activation energy for growth and shrinkage of SOI samples thicker than 800 A was found to be the same as bulk Si: 2.3 eV (growth) and 4.6 eV (shrinkage). Bulk silicon implanted with low doses of oxygen, permitted investigation of the nucleation sites of SFs in SIMOX where oxygen precipitates are believed to act as nuclei for SFs. A five step etch procedure was modified to reveal the defects in very thin SOI and an automatic defect counting system developed at T.C.D. permitted fast and reliable measurements of size and density of the defects. It appears that the two Frank partial dislocations that bound SFs, are pinned at the two Si/Si02 interfaces for both SIMOX and BESOI films thinner than 500 Å. In thicker SOI, the mechanisms for growth and shrinkage of SFs are the same as for bulk silicon.

Investigation of Structural Stability in 4H-SiC Structures with Heavy Ion Implanted Interface

2006 ◽  
Vol 527-529 ◽  
pp. 395-398 ◽  
Author(s):  
Augustinas Galeckas ◽  
Anders Hallén ◽  
Adolf Schöner ◽  
Jan Linnros ◽  
P. Pirouz
Keyword(s):  
Imaging Spectroscopy ◽  
Stacking Faults ◽  
Heavy Ion ◽  
High Energy ◽  
Irradiation Damage ◽  
Impurity Atoms ◽  
Nucleation Sites ◽  
Comprehensive Picture ◽  
Cvd Growth ◽  
Homoepitaxial Layers

We investigate the possibility of controlling formation of stacking faults (SFs) at the interface region by implanting the 4H-SiC substrate with low-energy antimony ions (75 keV Sb+) prior to conventional CVD growth of the homoepitaxial layers. This approach is based on the solidsolution hardening concept, according to which interaction of impurity atoms with dislocations makes the motion of the latter more difficult. Photoluminescence imaging spectroscopy is employed to investigate incorporation of Sb+ implants at the buried interface and also to assess its impact on structural degradation. Spectral results are analyzed considering both the onset of n-type doping and irradiation damage. The latter factor was estimated separately from supplementary measurements of high-energy (2.5 MeV H+) proton-irradiated 4H-SiC epilayers. We compare results of optically stimulated SF formation in virgin and Sb implanted regions and provide a comprehensive picture of the defect evolution, including microscopic details of the imminent nucleation sites.

Modelling the X-ray powder diffraction of nitrogen-expanded austenite using the Debye formula

2008 ◽  
Vol 41 (3) ◽  
pp. 537-543 ◽  
Author(s):  
Jette Oddershede ◽  
Thomas L. Christiansen ◽  
Kenny Ståhl
Keyword(s):  
Dislocation Density ◽  
Powder Diffraction ◽  
Stacking Faults ◽  
Screw Dislocations ◽  
X Ray ◽  
Debye Formula ◽  
Interstitial Nitrogen ◽  
Expanded Austenite

Stress-free and homogeneous samples of nitrogen-expanded austenite, a defect-rich f.c.c. structure with a high interstitial nitrogen occupancy (between 0.36 and 0.61), have been studied using X-ray powder diffraction and Debye simulations. The simulations confirm the presence of deformation stacking faults in the structure, while twin or growth faulting can be ruled out. Screw dislocations are abundant and the dislocation density increases with the interstitial nitrogen occupancy. Whether the N atoms are clustered or distributed randomly among the octahedral interstices was found to be indistinguishable to X-ray powder diffraction.

Localized heat flow and Tertiary mineralization in southern New Mexico

Geophysics ◽  
1983 ◽  
Vol 48 (9) ◽  
pp. 1212-1218
Author(s):  
Gary W. Zielinski ◽  
Gail Moritz DeCoursey
Keyword(s):  
New Mexico ◽  
Heat Flow ◽  
Heat Source ◽  
Heat Production ◽  
Convective Instability ◽  
Local Scale ◽  
Surface Heat ◽  
The Body ◽  
Hydrothermal Mineralization ◽  
Granitic Intrusion

Eight shallow (<100 m deep) relative heat flow determinations from southern New Mexico reveal a systematic 3 HFU [Formula: see text] increase occurring within a distance of 2 km. The maximum surface heat flow appears roughly to overlie a Tertiary granitic body at a depth of about 600 m within an area of known hydrothermal mineralization. The presence of the anomaly, believed to be of subsurface origin, implies an active heat source centered at a depth of 1140 m, perhaps associated with hydrothermal circulation. Higher radioactive heat production in granites may contribute to convective instability and explain the apparent lateral coincidence between the anomaly and the body. This situation appears, on a local scale, analogous to coinciding zones of high present‐day heat flow and mineralization in England and Wales (Brown et al, 1980). In both cases, mineralization is associated with granitic intrusion that has occurred at a previous time which is much greater than the thermal time constant for cooling bodies. Shallow heat flow determinations may be useful in locating other similar areas and investigating possible associations of mineralization and thermal history.

Performance of Silicon Carbide PiN Diodes Fabricated on Basal Plane Dislocation-Free Epilayers

2006 ◽  
Vol 527-529 ◽  
pp. 371-374 ◽  
Author(s):  
Ze Hong Zhang ◽  
A.E. Grekov ◽  
Priyamvada Sadagopan ◽  
S.I. Maximenko ◽  
Tangali S. Sudarshan
Keyword(s):  
Basal Plane ◽  
Stacking Faults ◽  
Surface Damage ◽  
Induced Current ◽  
Pin Diodes ◽  
Current Stressing ◽  
Forward Current ◽  
Nucleation Sites ◽  
Basal Plane Dislocation ◽  
Electron Beam Induced Current

The nucleation sites of stacking faults (SFs) during forward current stress operation of 4H-SiC PiN diodes were investigated by the electron beam induced current (EBIC) mode of scanning electron microscopy (SEM), and the primary SF nucleation sites were found to be basal plane dislocations (BPDs). Damage created on the diode surface also acts as SF nucleation sites. By using a novel BPD-free SiC epilayer, and avoiding surface damage, PiN diodes were fabricated which did not exhibit SF formation under current stressing at 200A/cm2 for 3 hours.

METAMORPHISM OF THE MEGUMA GROUP OF NOVA SCOTIA

1966 ◽  
Vol 3 (7) ◽  
pp. 959-974 ◽  
Author(s):  
F. C. Taylor ◽  
E. A. Schiller
Keyword(s):  
Nova Scotia ◽  
Regional Metamorphism ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Contact Metamorphism ◽  
Granitic Rocks ◽  
Structural Elements ◽  
Early Ordovician ◽  
Quartz Veins ◽  
Granite Emplacement

The Meguma group of lithic greywacke, feldspathic quartzite, slate siltstone, and argillite is Early Ordovician or older in age and has undergone both regional and contact metamorphism. Both types of metamorphism have resulted in recrystallization and locally in orientation of newly formed minerals. Metasomatism and retrogressive metamorphism are subordinate and only locally important. Regionally metamorphosed rocks are divided into greenschist and almandine–amphibolite facies, although some assemblages cannot be assigned with certainty. Locally, biotite and garnet isograds are mappable within the greenschist zone.Relationships between regional metamorphism and structural elements (folding) show that deformation preceded regional metamorphism. Intrusion of granitic rocks has produced a zone of contact metamorphism (hornblende–hornfels facies) that is superimposed upon regional greenschist facies rocks, which shows that granite emplacement occurred after the regional grade was reached. Gold–quartz veins are confined to areas lying in the greenschist zone of regional metamorphism, which suggests that the almandine–amphibolite zone is not favorable.

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