X-ray topography of natural beryl using synchrotron and conventional sources

1983 ◽  
Vol 16 (1) ◽  
pp. 47-56 ◽  
Author(s):  
N. Herres ◽  
A. R. Lang
Keyword(s):  
Synchrotron Radiation ◽  
Radiation Damage ◽  
Continuous Spectrum ◽  
Lattice Defects ◽  
Growth Sector ◽  
X Ray ◽  
Diffraction Contrast

Continuous-spectrum synchrotron-radiation Laue transmission topographs of natural beryl have been compared with the corresponding projection topographs taken with conventional apparatus and Cu Kα 1 and Mo Kα 1 radiations in an analysis of configurations of grown-in lattice defects and of the diffraction contrast they produce. The natural defects studied included grown-in dislocations, impurity zoning and fault surfaces. A growth-sector map was constructed for the (0001) specimen slice examined. Differences of contrast among the various reflections appearing on the synchrotron-radiation topographs are discussed and it is demonstrated that the contrast characteristics of the synchrotron-radiation images which consist of a superimposition of 3{\bar 2\bar 1}1 and 6{\bar 4 \bar 2}2 reflections can be satisfactorily synthesized by a weighted superimposition of the 3{\bar 21}1 image recorded with Cu Kα 1 and the 6{\bar 4\bar 2}2 with Mo Kα 1. Synchrotron-radiation damage to the crystal manifested itself on the X-ray topographs both as area contrast and as contrast at the periphery of the irradiated area, yet no visual absorption or birefringence due to this damage was detected. Annealing at 770 K for 3 h completely removed the contrast due to radiation damage.

Synchrotron Radiation Damage Mechanism of X-Ray Mask Membranes Irradiated in Helium Environment

1992 ◽  
Vol 31 (Part 1, No. 12B) ◽  
pp. 4459-4462 ◽  
Author(s):  
Tomiyuki Arakawa ◽  
Hiroshi Okuyama ◽  
Koichi Okada ◽  
Hiroyuki Nagasawa ◽  
Tsutomu Syoki ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Radiation Damage ◽  
Damage Mechanism ◽  
X Ray

scholarly journals Soft X-Ray Microscopy Radiation Damage On Fixed Cells Investigated With Synchrotron Radiation FTIR Microscopy

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
A. Gianoncelli ◽  
L. Vaccari ◽  
G. Kourousias ◽  
D. Cassese ◽  
D. E. Bedolla ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Radiation Damage ◽  
Ftir Microscopy ◽  
X Ray

On the growth-sectorial dependence of defects in natural diamonds

1974 ◽  
Vol 340 (1621) ◽  
pp. 233-248 ◽  
Keyword(s):  
Growth Sector ◽  
X Ray Diffraction ◽  
Crystal Surfaces ◽  
X Ray ◽  
Flat Surfaces ◽  
Diffraction Contrast ◽  
Nitrogen Impurity ◽  
Growth History ◽  
Localized Defects ◽  
Good Lattice

Certain rare diamonds have had epochs of growth during which they were bounded by two surface forms: normal {111} facets together with non­-flat surfaces of mean {100} orientation (‘cuboid’ surfaces). Differences of lattice imperfection content in octahedral and cuboid growth sectors (i. e. in regions that had crystallized respectively on {111} facets or on cuboid surfaces) have been studied by birefringence, ultramicroscopy, cathodoluminescence and various X-ray topographic techniques in­cluding X-ray topographic recording of the intensity of the anomalous ‘spike’ X-ray reflexions which are due to {100}-orientation-platelet pre­cipitates. Dissimilar manifestations of combined octahedral and cuboid growth are illustrated in the growth histories of three specimens in­ tensively examined. The sequence of relative development of octahedral and cuboid growth is found by mapping X-ray topographically both the differences in texture presented by the X-ray images of octahedral com­pared with cuboid growth material, and the diffraction contrast at growth-sector boundaries which arises from oherency strains of localized defects in the boundaries. The ratio of growth rates on {111} compared with cuboid surfaces may vary continuously and smoothly during a sub­ stantial part of the crystal’s growth history, or may have major or minor discontinuities. Particles ranging up to micrometre sizes are found dis­persed in cuboid growth sectors. They can be detected by the X-ray diffraction contrast they generate through straining the diamond matrix surrounding them. They may be resolved individually by ultramicroscopy (if the specimen shape is favourable), and by their individual diffraction-contrast images (provided that inter-particle distances exceed a few micro metres). In some parts of one specimen a dense sheet of particles coincides with the growth-sector boundaries at which adjacent cuboid growth sectors met, and a zone about 20 μm thick on each side of the boundary is depleted of particles. As to whether the bodies are precipitates or inclusions the X-ray topographs show no instances of ‘grown-in’ dislocations originating at the particles (such as are often observed at inclusions of micrometre sizes and greater which have been trapped at growing crystal surfaces), and the few dislocations observed which issue from regions dense in diffraction-contrast-producing bodies are themselves ‘decorated' by apparently similar bodies. These observations favour precipitation, but do not exclude the possibility that the bodies are entirely inclusions. They also admit the possibility that the present size of the bodies was attained through post-growth segregation upon smaller inclusions. Cuboid-growth material not distorted by the diffraction-contrast-producing bodies can exhibit a low integrated Bragg reflexion, indicating very good lattice perfection. Octahedral-growth material Bragg reflects more strongly (sometimes markedly so) indicating unresolved lattice imperfections finely distributed. Octahedral growth sectors show strong ‘spike’ reflexions in comparison with cuboid sectors; and where the diamond matrix integrated reflexion is lowest, ‘spike’ reflexion is weakest. The ‘spike’ topographs show that the density of {100}-orientation platelets (presumably largely nitrogen impurity) is less (sometimes much less) in cuboid than in octahedral-growth material of similar epoch. It is suggested that {111} facets of diamond act as sinks for nitrogen present in the surrounding growth medium.

On the variation of X-ray diffraction contrast with wavelength: A study with synchrotron radiation

1983 ◽  
Vol 16 (1) ◽  
pp. 113-125 ◽  
Author(s):  
A. R. Lang ◽  
A. P. W. Makepeace ◽  
M. Moore ◽  
W. C. Machado
Keyword(s):  
Synchrotron Radiation ◽  
Natural Diamond ◽  
Growth Surface ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Contrast ◽  
Theoretical Predictions ◽  
Fluorine Ions ◽  
Fracture Damage ◽  
Polished Plate

Diffraction contrast phenomena on X-ray topographs taken with continuous-spectrum synchrotron radiation have been studied at wavelengths of 0.057, 0.064, 0.071, 0.100, 0.154, 0.206 and 0.250 nm. The specimen was a polished plate of natural diamond with surfaces parallel to (110), ½ mm thick. Using the {\bar 1}11 reflection and a stored electron beam energy of 1.8 GeV all topographs (except that taken with λ = 0.25 nm) were harmonic free. The specimen exhibited mixed-habit growth, containing sectors of normal faceted {111} growth and sectors of non-faceted `cuboid' growth in which growth-surface orientation was variable and only approximately parallel to {100}. Prior to X-ray topography the specimen had received localized damage from implantation with fluorine ions of 17 MeV energy. Features whose variation with wavelength was studied included (1) the relative strengths of integrated reflections from {111} and `cuboid' growth sectors, (2) the intensity of `spike' disorder diffuse reflections relative to sharp Bragg reflections, (3) contrast from inclusions, polishing striae and fracture damage and (4) lattice bending and diffraction contrast at the sites of fluorine ion implantation. Theoretical predictions of the wavelength variation of the intensity of the diffuse reflection images and of contrast due to resolved defects showed good agreement with the observations.

Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation

1992 ◽  
Vol 50 (2) ◽  
pp. 1038-1039
Author(s):  
Shawn Williams ◽  
Xiaodong Zhang ◽  
Susan Lamm ◽  
Jack Van’t Hof
Keyword(s):  
Visible Light ◽  
Radiation Damage ◽  
Cross Section ◽  
Imaging Techniques ◽  
Dose Range ◽  
Specimen Preparation ◽  
X Rays ◽  
Metaphase Chromosomes ◽  
X Ray ◽  
Scanning Transmission

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.

Characterization of defects in tabular silver halide grains

1990 ◽  
Vol 48 (4) ◽  
pp. 1046-1047
Author(s):  
C. Goessens ◽  
D. Schryvers ◽  
J. Van Landuyt ◽  
A. Verbeeck ◽  
R. De Keyzer
Keyword(s):  
Radiation Damage ◽  
Silver Halide ◽  
Chemical Characteristics ◽  
X Ray ◽  
Free Region ◽  
Central Defect ◽  
Crystallographic Defects ◽  
Physical And Chemical ◽  
Two Sides

Silver halide grains (AgX, X=Cl,Br,I) are commonly recognized as important entities in photographic applications. Depending on the preparation specifications one can grow cubic, octahedral, tabular a.o. morphologies, each with its own physical and chemical characteristics. In the present study crystallographic defects introduced by the mixing of 5-20% iodide in a growing AgBr tabular grain are investigated. X-ray diffractometry reveals the existence of a homogeneous Ag(Br1-xIx) region, expected to be formed around the AgBr kernel. In fig. 1 a two-beam BF image, taken at T≈100 K to diminish radiation damage, of a triangular tabular grain is presented, clearly showing defect contrast fringes along four of the six directions; the remaining two sides show similar contrast under relevant diffraction conditions. The width of the central defect free region corresponds with the pure AgBr kernel grown before the mixing with I. The thickness of a given grain lies between 0.15 and 0.3 μm: as indicated in fig. 2 triangular (resp. hexagonal) grains exhibit an uneven (resp. even) number of twin interfaces (i.e., between + and - twin variants) parallel with the (111) surfaces. The thickness of the grains and the existence of the twin variants was confirmed from CTEM images of perpendicular cuts.

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