bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission Electron Microscope Investigations Of Defects Produced By Individual Displacement Cascades In Si And Ge
Authors: Ruault M. O. , Jäger W. 
Published: August 2011

SUMMARYMonocrystalline {111} Si and Ge specimens have been irradiated with atomic and molecular heavy ions in order to study the influence of the cascade energy density and the interaction between displacement cascades on the defect production. Transmission electron microscope (TEM) studies were performed to investigate the defect parameters. After atomic irradiation of Si and Ge the defects analysed (typical size 3–5 nm) are of interstitial type. Both defects with three‐dimensional strain centres and defects with a strongly asymmetric strain field were observed. An analysis of the yield and the defect size in Si as a function of ion dose suggests that the defects are formed within individual cascades rather than by a process involving overlapping cascades. Changes of the energy density locally deposited in the lattice do not affect yield and size significantly. Under otherwise similar experimental conditions, the average defect depth is significantly larger for Bi2+ irradiations than for Bi+ irradiations.
Extended Screw Dislocation Networks In Silicon
Authors: Gwinner D. , Packeiser G. , Labusch R. 
Published: August 2011

SUMMARYTwisting silicon single crystals around a <111>‐axis and subsequent annealing produces a high fraction of screw dislocations that are arranged in hexagonal networks as is shown by TEM investigations. A maximum fraction of screws is obtained with a twist angle of 24° mm−1 and an annealing time of 4 h at 1420 K. Using stereopairs, the spatial structure of the networks was investigated. The dislocation structure in as‐deformed samples is regarded as an initial state from which hexagonal networks can be formed during heating. A weak beam analysis reveals two types of intrinisic‐extrinsic node pairs, one of which is considered to be a possible intermediate stage of the formation processes. An explanation is given, taking dislocation cross‐slip and climb into consideration.
Microscopy Of Semi‐Insulating Gallium Arsenide
Authors: Augustus P. D. , Stirland D. J. 
Published: August 2011

SUMMARYOptical and electron microscopy examinations of a wide range of semi‐insulating, n‐type and (one) p‐type single crystal {001} gallium arsenide specimens have been made. It has been found that grown‐in line dislocations are decorated with small (50–100 nm diam.) precipitates in all these specimens. Energy dispersive X‐ray analysis and spark source mass spectrometry data have been employed in attempts to identify the precipitates.
Use of fast X‐ray film for low‐fluence biological electron microscopy at 100 kV and 1000 kV
Authors: Parsons Donald F. , Marko Michael , King Murray Vernon 
Published: August 2011

SUMMARYA user evaluation has been made by electron microscopists of an X‐ray film for routine electron microscopy. The recent improvements in mammographic X‐ray films, with the attempt to reduce the patient dose required to produce a high‐resolution mammogram, have resulted in some useful films for medium‐ and high‐voltage electron microscopy. They can yield essential cytological information with a reduction of the electron fluence (exposure) applied to the specimen of more than an order of magnitude compared with conventional electron‐microscope films. Their use is indicated in situations where beam damage is severe.
A simple preparation, for microscopical investigations, of monolayered cells at specific cell‐cycle stages
Authors: Gwynn I. Ap , Meredith R. W. J. 
Published: August 2011

SUMMARYA technique is described whereby cells at the mitotic stage are washed off into specially designed culture tubes. Because these tubes have a small culturing area in relation to the volume of medium they contain, and the area of the original culture flask, a usable number of cell‐cycle synchronized cells are obtainable for microscopical study.
Phase separation in alcohol/liquid carbon dioxide solvent systems facilitates critical point drying
Authors: Mckanna James A. , Lempka Tim 
Published: August 2011

SUMMARYCarbon dioxide and methanol or ethanol, although miscible, form alcohol/CO2 solutions that do not easily mix with additional pure liquid CO2. If the CO2 inlet is situated at the top of a critical point drying apparatus chamber, pure CO2 will entirely displace the alcohol/CO2 phase (which is more dense) while keeping the chamber filled with liquid. This unexpected phenomenon is invaluable in critical point drying delicate biological tissues which remain continuously immersed, avoiding surface or convection currents. By providing an objective criterion for intermediate solvent displacement, the protocol also eliminates ambiguous ‘flushing’ steps.
A method for providing comparative counts of small particles in electron microscopy
Authors: Roberts I. M. 
Published: August 2011

SUMMARYA method for estimating the relative concentrations of particles by electron microscopy is described. The method involves the determination of the area of the field of view in the microscope binoculars, relative to a standard area, and is independent of grid type, magnification, operator or microscope. Particle counts using this method are in close agreement with counts made from electron micrographs. The method is simple, rapid and reproducible, and, for low numbers of particles, more accurate than conventional methods.
Advances in the electrical assessment of semiconductors using the scanning electron microscope
Authors: Davidson S. M. , Dimitriadis C. A. 
Published: August 2011

SUMMARYRecent developments in the application of the SEM to semiconductor assessment are described. Formulae are presented for the calculation of the mean carrier density injected by the electron beam. A procedure for the correction of diffusion length measurements for surface recombination is outlined. Measured diffusion lengths and lifetimes in GaP agree well. Lifetime measurements, when applied to the study of dislocations in GaP, show that recombination occurs mainly at a Cottrell atmosphere of impurities/defects surrounding the dislocation.
Electron beam depth profiling in semiconductors
Authors: Possin G. E. , Kirkpatrick C. G. 
Published: August 2011

SUMMARYA technique for depth profiling of semiconductors is described based upon the measurement of induced junction currents as a function of beam energy. Using the known energy loss relation and electron hole pair generation rate it is possible to infer quantitative information about the semiconductor structures as a function of depth between ∼0·02 and ∼5 μm for silicon. Examples of the application of the technique to implanted and electron beam pulse annealed silicon and to a JFET transistor are described. Calculations of diffusion length limits, junction depths, poly‐silicon thickness, epitaxial layer thickness and surface recombination velocity are discussed.
A correlation between the electrical breakdown of silicon bipolar transistors and impurity precipitates
Authors: Augustus P. D. , Knights J. , Kennedy L. W. 
Published: August 2011

SUMMARYThe contamination of Si integrated circuits during B diffusion is shown to produce an α‐Fe precipitate which electrically degrades p‐n junctions. The precipitates are shown to strain the Si lattice inducing dislocations which can glide to other parts of the circuit.
SEM analyses of cathodoluminescence in MgO, CdS and GaAs/GaxAl1–xAs crystals
Authors: Datta S. , Aeberli K. E. , Boswarva I. M. , Holt D. B. 
Published: August 2011

SUMMARYThe method of analysis developed for the study of cathodoluminescence in the scanning electron microscope is briefly outlined. Current studies of cathodoluminescence in three types of crystal are presented. These are: (1) deformed and annealed MgO, (2) CdS into which Ga has been diffused, and (3) double heterostructure GaAs/GaxAl1–xAs laser material.
Diffusible ion localization by ion microscopy: a comparison of chemically prepared and fast‐frozen, freeze‐dried, unfixed liver sections
Authors: Stika Katherine M. , Bielat Kenneth L. , Morrison George H. 
Published: August 2011

SUMMARYThe necessity of low temperature preparative procedures for diffusible ion localization using the ion microscope has been established with rat liver as the test material. Using conventional fixation procedures, significant ion loss and redistribution were observed which exceeded the 1 μm lateral resolution of the direct imaging ion microanalyser. The compositional morphology evidenced in chemically prepared versus fast‐frozen, freeze‐dried, unfixed material was compared and evaluated in terms of ion retention, ion redistribution and morphological integrity. A mass spectral analysis of both preparations has been presented and discussed with regard to spectral interferences and elemental sensitivities. Ion images of sodium and potassium were recorded for chemically prepared liver sections and compared with the ion distributions obtained for unfixed, fast‐frozen, freeze‐dried 1 μm thick sections. The magnitude of ion loss during preparation of samples removed at different stages in the course of chemical processing was determined by atomic absorption and flame emission spectrophotometry.
Determination of the mean caliper diameter of lung nuclei by a method which is independent of shape assumptions
Authors: Woody Dawn , Woody Erik , Crapo James D. 
Published: August 2011

SUMMARYWhen determining the number of nuclei (therefore cells) present in a known volume of tissue it is necessary to determine the overall mean caliper diameter of nuclei for each cell type studied. Most previous methods for determining the mean caliper diameters (D̄) of cell nuclei were strongly dependent upon assumptions of the shape of the particles in question (Greeley et al., 1978). A computer program has now been designed to calculate D̄ from three‐dimensional reconstructions of nuclei in a manner that is independent of all shape assumptions. The D̄s of ten capillary endothelial cell nuclei from normal rat lungs have been determined by this shape‐independent method. The resulting overall mean caliper diameter for this group of ten nuclei varied only slightly from that previously estimated for them by a method which assumes them to be triaxial ellipsoids. In a similar comparison, the D̄s for ten normal human lung endothelial cell nuclei were determined by both methods. The overall mean caliper diameter determined by the shape‐independent method was 10% larger than that estimated by the shape‐dependent method. This suggests that human lung endothelial nuclei vary significantly from the shape assumption (triaxial ellipsoid) employed in the shape‐dependent method, and the shape‐independent method was considered to yield a more accurate measurement of D̄.
Scanning electron microscopic examination of the scolex and external tegumental surface of Proteocephalus ambloplitis
Authors: Jilek Reid , Crites John L. 
Published: August 2011

SUMMARYThis examination represents the first scanning electron microscopic study of a proteocephalid tapeworm, Proteocephalus ambloplitis, and it also serves as the first comparative study between the adult and larval stages of a tapeworm. Proteocephalus ambloplitis has numerous microtrichs whose densities and diameters differ greatly from those of cyclophyllidean and pseudophyllidean tapeworms previously examined. Proteocephalus ambloplitis also has an external apical organ and a subcuticular organ.
Differential sensitivity of neurosecretory and non‐neurosecretory neurones of an aphid to sucrose during fixation for electron microscopy
Authors: Hardie Jim 
Published: August 2011

SUMMARYThe Group 1 neurosecretory cells and a proportion of the non‐neurosecretory cells in the protocerebrum of the aphid Megoura viciae show gross differences in preservation when sucrose is used to increase the osmolarity of a glutaraldehyde primary fixative and an osmium tetroxide secondary fixative. The neurosecretory cells are well preserved whilst a proportion of the non‐neurosecretory cells are shrunken and electron dense, the proportion of affected cells increases with the concentration of sucrose used. This difference is not seen when either the primary or the secondary fixatives are used alone, when a mixture of the primary and secondary fixatives is used or when the osmotic pressure is increased with inorganic salts.
The observation of amorphous materials at high voltage and high resolution
Authors: Smith David J. , Saxton W. O. , Cleaver J. R. A. , Catto C. J. D. 
Published: August 2011

SUMMARYThin films of amorphous carbon, silicon and germanium have been examined at high resolution at accelerating voltages up to 575 kV with the Cambridge University high resolution electron microscope. The directly interpretable resolution has been demonstrated to extend to 0ṁ22 nm, so that the microscope is capable of providing unambiguous structural information at the atomic level. The observations of both carbon and silicon were, however, somewhat disappointing in that no significant specimen detail was revealed despite the improved performance compared with that of conventional 100 kV instruments. Some of the factors involved in observation and interpretation of these images are discussed.
Preliminary electron microscopical observations of defects in cold rolled amorphous Cu60Zr40
Authors: Chevalier J. P. 
Published: August 2011

SUMMARYAmorphous Cu60Zr40 alloy, prepared by a levitation melt and double roller quenching technique has been severely cold rolled. Preliminary observations show the presence of two kinds of defects with different morphologies. In both cases the defects have a contrast which corresponds to that for a lower projected atomic density at the defect.
Investigations of the structure of amorphous and partially crystalline metallic alloys by high resolution electron microscopy
Authors: Gaskell P. H. , Smith David J. 
Published: August 2011

SUMMARYA number of amorphous and partially crystalline palladium‐silicon alloys have been examined by high resolution transmission electron microscopy at 500 kV. With the directly interpretable resolution extending beyond the first peak in the structure factor at 0ṁ23 nm, details of the local microstructure at the atomic level are visible. Images of small metallic particles show a well‐defined pattern of fringes over local regions. In some instances, especially in partially‐ordered alloys, neighbouring or overlapping fringe patterns appear to be orientationally‐related in a similar manner to fringe systems seen in symmetrically multiply‐twinned particles. The significance of this type of structural examination for amorphous metals is discussed.
Fast computational procedures for the simulation of structure images in complex or disordered crystals: a new approach
Authors: Dyck D. Van 
Published: August 2011

SUMMARYDespite the important contribution of high‐resolution electron microscopy to materials science, the use of computer simulation as a reliable tool for the interpretation of the structure images in complex crystals or disordered solids has been limited seriously by the high computer demands of the available computational techniques.
Some ordering phenomena in the β Cu4Ti phase
Authors: Ecob Roger C. , Bee John V. , Ralph Brian 
Published: August 2011

SUMMARYThis paper presents further evidence concerning the structure of the β phase which forms as Widmanstätten or cellular precipitates in dilute copper‐titanium alloys. The effect of deformation in producing faults in this ordered phase is considered, and illustrations are provided of the resultant dislocation structures. The observation of some intrinsic disorder is discussed in terms of the influence of a simultaneous phase transformation on the order‐disorder transition.
The analysis of a defect in ordered Ag3Mg
Authors: Portier R. , Gratias D. , Guymont M. , Stobbs W. M. 
Published: August 2011

SUMMARYThe high resolution image of an apparently displacive defect in the long period ordered structure of Ag3Mg is analysed in terms of a simplified substitutional model. It is demonstrated by image simulation that the characteristics of the image could be described equally well on the basis of progressive relative substitution of Ag for Mg on two of the four sublattices in the structure.
High resolution imaging of defects in sigma phase in a stainless steel
Authors: Southwick D. , Stobbs W. M. 
Published: August 2011

SUMMARYThe high resolution axial lattice imaging technique has been applied to the study of the faults which commonly occur in the sigma phase which can be formed from ferrite in a duplex high chromium stainless steel on ageing at 973 K. It was noted that axial lattice fringe images at (001)σ show no detailed correspondences with thickness and it was further demonstrated that lattice fringe displacements in axial images at strain free boundaries can be used to give an accurate measure of the magnitude of the associated lattice displacements. The displacement vectors associated with the common (100)σ faults in the material were classified.
Intermediate transformation structures in silicon carbide
Authors: Jepps N. W. , Page T. F. 
Published: August 2011

SUMMARYIn order to examine the detailed structural origins of the confusing diffraction patterns often exhibited by partially transformed polytypic materials, HREM lattice imaging techniques have been used to examine directly the layer‐by‐layer stacking sequences in a range of samples of cubic (β) SiC partially transformed to α polytypes by high temperature annealing. A number of intermediate structures have been characterized, one of which provides the first direct evidence supporting an earlier model of the β→α transformation (Jagodzinski, 1971) in which three‐layer twins, separated by multiples of three layers, propagate through the cubic structure to produce a faulted haxagonal (6H) polytype. These observations, together with considerations of twin geometry, also suggest a means of co‐ordinating the sideways nucleation of 6H unit‐cell high steps, whose lengthways growth has been previously observed to effect the solid‐state β→α transformation (Jepps & Page, 1979).
Using RHEED to study polytypism
Authors: Gauthier J. P. 
Published: August 2011

SUMMARYUp to now, relatively few papers have dealt with electron beam investigations of polytypic substances. Recent work in SiC (Gauthier, 1978) pointed out the general interest in the use of reflection high energy electron diffraction (RHEED) for examining well‐ordered long‐period modifications. The main results are summarized here, showing what information can be obtained from RHEED patterns for the determination of polytype structures and hence possible explanations of growth mechanisms. In the same way, other materials have now been examined by the same technique and some results from zinc sulphide crystals are presented as an illustration. The mixtures of different ZnS modifications are complex; moreover, polytype disorder exists commonly in that substance. Such a situation vindicates the use of other techniques, particularly high resolution electron microscopy.
Structure‐staining relationships in histochemistry and biological staining
Authors: Horobin RichardW. 
Published: August 2011

SUMMARYA description is given of the choice, rationale and calculation of several numerical coefficients for describing the chemical structures of staining reagents such as dyestuffs, enzyme substrates, diazonium and tetrazolium salts. Using such coefficients, structure‐staining correlations may be made for many staining systems. Examples include the structural correlations of the quantitative affinity measurements of the staining of chromatin with basic dyes, the tetrazolium salts for use as visualizing agents in enzyme histochemistry, and the use of bis‐azo compounds as acid or basic dyes, or as fat stains. The value of such structure‐staining correlation models for assisting the rational selection and design of new histochemical reagents, and for understanding old reagents and procedures, is discussed.
Structure‐staining relationships in histochemistry and biological staining
Authors: Horobin RichardW. , Flemming Linda 
Published: August 2011

SUMMARYCorrelations between the structural features of dyes and staining performance for elastic fibres were investigated. Dyes studied included the traditional stains (such as Gomori's Aldehyde‐Fuchsin and Weigert's Resorcin‐Fuchsin), acid dyes used from alkaline aqueous‐organic solvent mixtures (the Horobin‐James system), and basic dyes used from acidic aqueous‐ethanolic mixtures (the Taenzer‐Unna system). In all three classes effective elastic fibre stains had large conjugated bond numbers, and were often hydrophobic (i.e. had high Hansch π values). By choosing dyes with conjugated bond numbers at or over a critical value (25 for the TU system, 35 for the HJ) it is possible to select new and effective dyes for use in the HJ and TU staining systems. Mechanistically these results support the view that for typical commercial dyes and also for the traditional stains van der Waals attractions provide the important contributions to dye‐elastic fibre affinities, with hydrophobic bonding playing a subsidiary role. However, supporting the views of Lillie, it was also noted that even hydrophilic dyes of low conjugated bond number could stain elastic fibres, if the dye carried a sufficiently reactive primary amino group as a substituent. The additional substituent groupings needed to generate such reactivity have been specified, for both acidic and alkaline reaction conditions.
The molecular biology of histochemical staining by cationic phthalocyanin dyes: the design of replacements for Alcian Blue
Authors: Scott J. E. 
Published: August 2011

SUMMARYFour cationic copper phthalocyanin dyes are compared with Alcian Blue 8G for specificity of interaction with a range of natural and synthetic polyanions. The CEC system is used to estimate dye‐substrate affinities.The results support the hypothesis that the tissue staining pattern of Alcian Blue is determined by (a) exclusion of the dye from polynucleotide stacked base pairs by steric hindrance due to bulky substituents on the chromophore and (b) the presence of pendant quaternary charges whose affinity for negative sites on polyanionic substrates is without regard for the precise chemical nature of the anion.These conclusions, and practical considerations lead to the choice of quaternized Astra Blue 6GLL as a replacement for Alcian Blue (now no longer manufactured).It is superior to Alcian Blue in pH range, and stability in solution. It is easily prepared from a readily available precursor.
On the mechanism of Mallory's phosphotungstic acid‐haematoxylin stain
Authors: Puchtler Holde , Waldrop FayeSweat , Meloan SusanN. 
Published: August 2011

SUMMARYThe mechanism of Mallory's (1900) phosphotungstic acid‐haematoxylin (PTAH) stain is not yet fully understood; staining properties vary with the age of the dye solution. In this study, a 1‐year‐old solution was employed as described previously. Paper chromatograms revealed blue, red and yellow components of phosphotungstic acid‐haematoxylin. Modification of reactive groups as well as consecutive treatment of sections with haematoxylin and phosphotungstic acid indicated hydrogen bond formation by the blue component. Substitution of brazilin for haematoxylin proved that two free phenolic ‐OH groups per dye residue are essential for binding of the blue phosphotungstic acid‐haematoxylin chelate. Uptake of the red fraction was determined by the polyacid moiety of the dye. Van der Waals forces presumably contributed to dye binding, but did not govern the selectivity of the red and blue components of PTAH for various tissue structures.