scholarly journals Trevor Evans. 26 April 1927 — 10 October 2010

2021 ◽  
Author(s):  
L. M. Brown ◽  
I. M. Mills
Keyword(s):  
Natural Diamond ◽  
High Energy ◽  
Dislocation Loops ◽  
Synthetic Diamonds ◽  
Transmission Electron ◽  
Ejection Process ◽  
De Beers ◽  
The Uk

Trevor Evans was responsible for revealing the main physical processes which take place in natural diamond both in the upper mantle of the earth, where it is stabilized by high pressure and temperature, and as it is ejected by volcanic action to the surface. By measuring the activation energies required for graphitization, he clarified the reason for its very long life as a metastable crystal, valuable both as a gemstone and as an industrial abrasive. He learned how to make diamond specimens for examination in the transmission electron microscope, which enabled his discovery of dislocation loops and platelet precipitates in nitrogen-containing (type 1) stones. In a series of exacting laboratory experiments under geologically relevant conditions he pioneered the study of the emergence of nitrogen from solution to precipitation during the ejection process. In synthetic diamonds, using high-energy electron irradiation, he was able to reproduce the sequence of all the various types of nitrogen aggregation found in natural diamond. His work played a major role underpinning the characterization of gemstones, explaining many features of their colour. For many years he led diamond research in the UK, supported by De Beers. His work stimulated and has been confirmed by research in many other laboratories around the world.

Reflection electron microscopy of as-grown diamond surfaces

1993 ◽  
Vol 51 ◽  
pp. 1006-1007
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Electron Microscopy ◽  
Synthetic Diamond ◽  
High Energy ◽  
Dark Field ◽  
Reverse Direction ◽  
Diamond Surfaces ◽  
Grain Sizes ◽  
Synthetic Diamonds ◽  
De Beers ◽  
Reflection Electron Microscopy

It has been found that the abrasion of diamond-on-diamond depends on the crystal orientation. For a {100} face, the friction coefficient for sliding along <011> is much higher than that along <001>. For a {111} face, the abrasion along <11> is different from that in the reverse direction <>. To interpret these effects, a microcleavage mechanism was proposed in which the {100} and {111} surfaces were assumed to be composed of square-based pyramids and trigonal protrusions, respectively. Reflection electron microscopy (REM) has been applied to image the microstructures of these diamond surfaces.{111} surfaces of synthetic diamond:The synthetic diamonds used in this study were obtained from the De Beers Company. They are in the as-grown condition with grain sizes of 0.5-1 mm without chemical treatment or mechanical polishing. By selecting a strong reflected beam in the reflection high-energy electron diffraction (RHEED) pattern, the dark-field REM image of the surface is formed (Fig. 1).

Structure Determination of Clusters Formed in Ultra-Low Energy High-Dose Implanted Silicon

2005 ◽  
Vol 108-109 ◽  
pp. 303-308 ◽  
Author(s):  
N. Cherkashin ◽  
Martin J. Hÿtch ◽  
Fuccio Cristiano ◽  
A. Claverie
Keyword(s):  
Electron Microscopy ◽  
Geometric Phase ◽  
Low Energy ◽  
High Dose ◽  
Dislocation Loops ◽  
Weak Beam ◽  
Transmission Electron ◽  
Geometric Phase Analysis

In this work, we present a detailed structural characterization of the defects formed after 0.5 keV B+ implantation into Si to a dose of 1x1015 ions/cm2 and annealed at 650°C and 750°C during different times up to 160 s. The clusters were characterized by making use of Weak Beam and High Resolution Transmission Electron Microscopy (HRTEM) imaging. They are found to be platelets of several nanometer size with (001) habit plane. Conventional TEM procedure based on defect contrast behavior was applied to determine the directions of their Burger’s vectors. Geometric Phase Analysis of HRTEM images was used to measure the displacement field around these objects and, thus, to unambiguously determine their Burger’s vectors. Finally five types of dislocation loops lying on (001) plane are marked out: with ] 001 [1/3 ≅ b and b ∝ [1 0 1], [-1 0 1], [0 1 1], [0 -1 1].

Characterization of neutron irradiation damage in zirconium alloys—an international “round-robin” experiment

1978 ◽  
Vol 36 (1) ◽  
pp. 366-367
Author(s):  
D.O. Northwood ◽  
R.W. Gilbert ◽  
P.M. Kelly ◽  
P.K. Madden ◽  
D. Faulkner ◽  
...  
Keyword(s):  
Zirconium Alloys ◽  
Round Robin ◽  
Irradiation Damage ◽  
Exact Nature ◽  
Dislocation Loops ◽  
The Past ◽  
Irradiation Growth ◽  
Transmission Electron ◽  
International Round

Over the past few years there has been disagreement between laboratories on the exact nature of the damage in irradiated zirconium alloys. The main disagreement has centred on whether or not dislocation loops with c-component Burgers' vectors are formed during the irradiation. Since the presence of c-component loops was required in one of the current theories of irradiation growth and is considered in many other models, it was desirable to clear up this point and others relating to the nature of the damage such as loop size, loop concentration and the nature of the loop population, i.e. vacancy or interstitial. To this end a ‘round-robin’ series of transmission electron microscopy (TEM) examinations of neutron irradiated zirconium alloys was organized and the results are reported herein.The participants in the ‘round-robin’ included laboratories who had previously claimed to have seen evidence for c-component damage. The materials examined included zirconium and Zircaloy-2 irradiated at temperatures from 250-400°C, Table 1, the materials irradiated at 400°C providing samples with dislocation loops large enough to determine the interstitial/vacancy nature by inside/outside contrast techniques.

New Developments in the Defect Structure of Implanted Furnace-Annealed Silicon on Sapphire

1981 ◽  
Vol 10 ◽  
Author(s):  
Eliezer Dovid Richmond ◽  
Alvin R. Knudson ◽  
Tom J. Magee
Keyword(s):  
Silicon Film ◽  
Stacking Faults ◽  
High Energy ◽  
Structural Defects ◽  
Dislocation Loops ◽  
Bulk Silicon ◽  
New Developments ◽  
Transmission Electron ◽  
Silicon Implantation ◽  
First Time

ABSTRACTThe structural defect properties of silicon on sapphire (SOS) are investigated with transmission electron microscopy and Rutherford backscattering. The results for as-grown SOS films are compared with SOS films which have been implanted with 1016 Si+ ions cm− 2 at an energy of 170 keV and annealed at 600°C (1 h) and 1000°C (18 h). The regrowth proceeds from the silicon surface even though it is noncrystalline as determined by reflection high energy electron diffraction. The structural defects consist of stacking faults, microtwins and dislocations. The stacking faults and microtwins show a dramatic reduction with processing. The nature of the structural defects at the interface after implantation and annealing is reported here for the first time. It is different from the bulk of the silicon film and consists of a layer of dislocation loops of various sizes and short dislocation lines which follow the interface and curve upwards. This behavior is analogous with the secondary defects generated in self-implanted bulk silicon. Suggestions, based on results from bulk silicon implantation, are made for optimizing the ion implantation furnace annealing process.

scholarly journals Comparison between magnetic properties of CoFe2O4 and CoFe2O4/polypyrrole nanoparticles

2018 ◽  
Vol 58 (3) ◽  
Author(s):  
Kęstutis Mažeika ◽  
Violeta Bėčytė ◽  
Yulia O. Tykhonenko-Polishchuk ◽  
Mykola M. Kulyk ◽  
Oleksandr V. Yelenich ◽  
...  
Keyword(s):  
Ball Mill ◽  
High Energy ◽  
Composite Nanoparticles ◽  
Specific Loss Power ◽  
Transmission Electron ◽  
High Energy Ball Mill ◽  
Energy Ball ◽  
Polypyrrole Nanoparticles ◽  
Polypyrrole Composite

CoFe2O4/polypyrrole composite nanoparticles were synthesized using a high energy ball mill. Mössbauer and Fourier transform infrared spectroscopies, magnetization measurements and transmission electron microscopy were used for the characterization of samples. Specific loss power (SLP) was determined by exposing nanoparticles to an alternating magnetic field. Some changes in coercivity were observed and explained comparing CoFe2O4 nanoparticles withCoFe2O4/polypyrrole composite nanoparticles.

Characterization of Si MBE Layers Doped in Situ by As Ion Beams

1987 ◽  
Vol 102 ◽  
Author(s):  
Max L. Swanson ◽  
N.R. Parikh ◽  
T.E. Jackman ◽  
D.C. Houghton ◽  
M.W. Denhoff
Keyword(s):  
Structural Damage ◽  
Electrical Activation ◽  
Dislocation Loops ◽  
Electrical Measurements ◽  
Implantation Energy ◽  
Mbe Growth ◽  
Transmission Electron ◽  
High Concentrations

ABSTRACTTo achieve high concentrations and electrical activation of As in Si without subsequent annealing, 500-3000 eV As + ions were implanted during MBE growth of Si at 450-840°C. The epitaxial layers were characterized by Rutherford backscattering/channeling, transmission electron microscopy, secondary ion mald spectroscopy, and electrical measurements. Samples containing 1.2×1020 As cm-3 grown at 700°C showed little damage, high As substitutionality and high electrical activation. However, similarly doped layers grown at 460°C showed lower As activation and varying amounts of structural damage. In one case, a band of damage near the Si substrate was observed which persisted even after rapid thermal annealing at 1120°C (10 s); the damage was characterized by a dechanneling step, non-substitutional As atoms and dislocation loops. A sample grown at 460°C with a high implantation energy (3 keV) was highly defected.

Nucleation and Growth of {113} Defects and {111} Dislocation Loops Insilicon-Implanted Selicon

1997 ◽  
Vol 469 ◽  
Author(s):  
G. Z. Pan ◽  
K. N. Tu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Microstructural Characterization ◽  
Nucleation And Growth ◽  
Growth Behavior ◽  
Dislocation Loops ◽  
Cross Sectional ◽  
Plan View ◽  
Transmission Electron

ABSTRACTPlan-view and cross-sectional transmission electron microscopy have been used to study the microstructural characterization of the nucleation and growth behavior of {113} rodlike defects, as well as their correlation with {111} dislocation loops in silicon amorphized with 50 keV, 36×1014 Si/cm2, 8.0 mAand annealed by rapid thermal anneals at temperatures from 500 °C to 1100 °C for various times. We found that the nucleations of the {113} rodlike defects and {111} dislocation loops are two separate processes. At the beginning of anneals, excess interstitials accumulate and form circular interstitial clusters at the preamorphous/crystalline interface at as low as 600 °C for 1 s. Then these interstitial clusters grow along the <110> direction to form {113} rodlike defects. Later, while the {113} defects have begun to grow and/or dissolve into matrix, the {111} faulted Frank dislocation loops start to form. We also found that the initial interstitial clusters prefer to grow along the <110>directions inclined to the implantation surface.

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