bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Historical Account Of The Development And Applications Of The Negative Staining Technique To The Electron Microscopy Of Viruses
Authors: Horne R. W. , Wildy P. 
Published: August 2011

SUMMARYA brief historical account of the development and applications of the negative staining techniques to the study of the structure of viruses and their components as observed in the electron microscope is presented.Although the basic method of surrounding or embedding specimens in opaque dyes was used in light microscopy dating from about 1884, the equivalent preparative techniques applied to electron microscopy were comparatively recent. The combination of experiments on a sophisticated bacterial virus and the installation of a high resolution electron microscope in the Cavendish Laboratory, Cambridge, during 1954, subsequently led to the analysis of several important morphological features of animal, plant and bacterial viruses. The implications of the results from these early experiments on viruses and recent developments in negative staining methods for high resolution image analysis of electron micrographs are also discussed.
Total quantitative recording of elemental maps and spectra with a scanning microprobe
Authors: Legge G. J. F. , Hammond I. 
Published: August 2011

SUMMARYA system of data recording and analysis has been developed by means of which simultaneously all data from a scanning instrument such as a microprobe can be quantitatively recorded and permanently stored, including spectral outputs from several detectors. Only one scanning operation is required on the specimen. Analysis is then performed on the stored data, which contain quantitative information on distributions of all elements and spectra of all regions.
Complementary freeze‐fracture, freeze‐etch specimens
Authors: Steere Russell L. , Erbe Eric F. 
Published: August 2011

SUMMARYA procedure is described for the preparation and comparison of complementary freeze‐fracture‐freeze‐etch specimens. These complementary replicas reveal the value of etching some specimens even when the cryoprotectant concentration amounts to as much as 25% glycerol and 25% sucrose. As expected, the peplomers on the outer surface of the surrounding membrane of potato yellow dwarf virus are clearly revealed on the etched specimens but nearly invisible in the complementary freeze‐fracture specimen. Unexpected differences in the internal structure of vesicles within a freeze‐etched chloroplast have been revealed. The cross‐fractured surfaces of some other vesicles have a rough structure, whereas the complementary freeze‐etch surfaces, also shadowed at 123 K, are extremely smooth, suggesting that the contents must have been liquid at 175 K. Large ice crystals form within tobacco mosaic virus (TMV) crystals in infected cells frozen rapidly without cryoprotectant. Cryoprotectant consisting of 25% glycerol and 25% sucrose prevents formation of ice crystals when these specimens are frozen under the same conditions. When cryoprotectant concentrations are decreased from the above level, ice crystals within the TMV crystals are often clearly demonstrated in the freeze‐etch specimen but not in the complementary freeze‐fracture specimen. These results suggest that the complementary freeze‐fracture‐freeze‐etch procedure and the extremely fragile TMV crystalline inclusions are ideal for examining the value of various cryoprotectants and the effect of freezing rates, etching temperatures, and etching times on the final image.
Imaging modes in confocal scanning light microscopy (CSLM)
Authors: Brakenhoff G. J. 
Published: August 2011

SUMMARYThe optical arrangement for confocal scanning light microscopy can be incorporated in various imaging modes. Light microscopical specimens can be imaged with contrast enhanced, under γ‐control, inverted, etc. In interference, conditions can be set such that either pure phase or pure amplitude images result. Stereoscopic images at arbitrary aspect ratios can be realized in CSLM by electronic processing of the data obtained when the specimen is sampled with more than one confocal point concurrently. Also forms of differential imaging either amplitude or phase are possible. The coupling of these imaging modes with the improved resolving powers of CSLM results in some unique imaging opportunities, especially of value for high resolution light microscopy of living specimens.
Ultrastructure of red cells frozen with hydroxyethyl starch
Authors: Allen Edward D. , Weatherbee Lee 
Published: August 2011

SUMMARYThe freeze fracture appearance of red cells frozen in the presence of varying concentrations of hydroxyethyl starch (HES) is described. A technique is used which allows examination of a small portion of cells from a larger unit. The frozen cells appear distorted probably as a result of osmotic dehydration but indicate no evidence of intracellular ice. The frozen mixture with HES has three phases—a particulate phase consisting of the concentrated HES (and other salts), a sculptured ice phase and the red cells. When the concentration of HES is increased, the particulate phase becomes more prominent and at 14% HES appears to surround nearly all cells. In cells frozen in saline alone and 4% HES, the cytoplasm in a majority of cells has numerous cavities and depressions. Since such units haemolyse badly when thawed, it is possible that these regions indicate structural damage. In contrast, those units frozen with 14% HES (in which nearly 85% of the cells survive freeze‐thaw) possess cells which only infrequently have such regions in the cytoplasm.
Modification of an SEM for backscattered electron imaging at low vacuum
Authors: Kazmierski T. M. , Millington P. F. 
Published: August 2011

SUMMARYModifications to the Cambridge Scanning Electron microscope enable the viewing of untreated insulating materials directly with no evidence of charging. Beam damage under the conditions employed were quite small, even uncoated polythene could be viewed at magnifications of 20–2000 at 30 keV for long periods of time with little evidence of continuing changes in surface structure. Detailed descriptions of the modifications used are given. Studies on biological material were not satisfactory and work is in progress to confirm that the claims of Robinson (1975a) can be demonstrated in this type of instrument.
Energy Spectra Of Dislocations In Silicon And Germanium
Authors: Schröter Wolfgang , Scheibe Ernst , Schoen Helmut 
Published: August 2011

SUMMARYThe properties of edge‐type dislocations are strongly dependent on the temperature at which they have been introduced into the crystal. Dislocations produced at T < 0·6 Tm (Tm melting point) exhibit a richer variety of properties than those introduced at T > 0·6 Tm: in germanium a strong increase of the hole density, in silicon an electron para‐magnetic resource (EPR)‐signal, showing many fine details, and several peaks in the deep level transient spectroscopy (DLTS)‐signal, are only found after low‐temperature deformation. The increase in the hole density has been ascribed to point defect clouds, which surround the dislocation, and seem to control their mobility. The clouds are not stable at the deformation temperature.The electrical and optical properties of edge‐type dislocations, introduced at T > 0·6 Tm into germanium, can be interpreted in terms of a half‐filled one‐dimensional band (for T ≥ 50 K), which might be due to dangling bonds in the dislocation core. In silicon the experimental data indicate a similar form of the local energy spectrum at dislocations.
Interstitial Supersaturation And Climb Of Misfit Dislocations In Phosphorus‐Diffused Silicon
Authors: Strunk H. , Gösele U. , Kolbesen B. O. 
Published: August 2011

SUMMARYBipolar transistors showing the‘emitter‐push effect’ have been investigated by transmission electron microscopy. From the analysis of isolated dislocation helices in the boron base and the phosphorus emitter it is concluded that the diffusion of phosphorus into silicon is coupled with a supersaturation of silicon self‐interstitials. A new generation mechanism for this supersaturation is suggested.
The Nature And Origin Of {113} Faults In Irradiated Silicon And Germanium
Authors: Salisbury I. G. 
Published: August 2011

SUMMARYAt elevated temperatures, electron irradiation damage in silicon and germanium forms faulted defects on {113} which are elongated in <110>. During the present work on silicon, these {113} faults were observed to unfault, apparently by glide, to give elongated interstitial loops with b = a/2<110>. Since the tetrahedral interstitial sites between adjacent {113}s form a full {113}, in both number and distribution, it was concluded that the atoms were accommodated in these positions.A fault of this type comprises interstitial pairs, the atoms of which are on adjacent tetrahedral sites a/4<111> apart, and it is proposed that these already exist, or are formed, when a fault nucleates. Two‘di‐interstitials’ then close‐pack along one of the three <110>s normal to their <111> axis, thus nucleating a {112} loop. This is unable to grow in any direction other than <110>, because its habit plane is occupied by matrix atoms, so the loops become extended. The defect grows in width by nucleating further loops on {112} planes, extended parallel to the first, and the‘array’ forms an elongated {113} defect, on a plane 10° from the original {112}. This gives the observed faulted {113} loops, elongated in <110>, with R ≃/11<113>.
Electron Microscope Study Of Microtwins In Epitaxial Silicon Films On Sapphire
Authors: Lihl R. , Oppolzer H. , Pongratz P. , Skalicky P. , Svanda W. 
Published: August 2011

SUMMARYSilicon on sapphire films were studied by TEM. The density of microtwins were closely investigated and a non‐uniform distribution with respect to the four {111} twinning planes was found. Crystallographic arguments are given to explain this non‐uniform distribution and the decrease of the fault density with the distance from the interface. Contrast analysis of the microtwins shows that most of them are not 3N‐layer twins but contain a stacking fault.
Characterization Of Grain Boundaries Observed In Polycrystalline Silicon For Solar Cell Applications
Authors: Fontaine Chantal , Rocher André 
Published: August 2011

SUMMARYThis paper describes some preliminary results concerning the TEM observations of grain boundaries in polycrystalline silicon for solar cell applications. A graphical method of grain boundary characterization has been developed. All the grain boundaries studied have been found to be characterized by twin relationships.
Electron Microscope Studies Of Vpe Gainas Layer Structures Suitable For Use As Infrared Leds
Authors: Hockly M. , Al‐Jassim M. , Booker G. R. , Nicklin R. 
Published: August 2011

SUMMARYElectron microscope investigations have been carried out on vapour grown (100) GaAs/GaInAs structures designed for use as infrared emitters of wavelength 1·06 μm. The structures consist of a GaAs substrate, a graded layer in which the indium concentration is increased from zero to 17 atomic %, and a constant composition Ga0·83In0·17As layer which contains a p‐n junction. X‐ray microprobe analysis of cross‐sections of the slices established the uniformity of the grading. TEM analysis showed a dense and extensive asymmetric network of misfit dislocations (1 × 1012 m−2 (108 cm−2)) in the graded layer, threading dislocations and other anomalous contrast features extending from the graded layer through the p‐n junction to the surface (local densities of 1 × 1011–1 × 1012 m−2 (107–108 cm−2)), and a planar network of dislocations just below the surface (spacing 0·2–2 μm). SEM EBIC and CL studies of the layer above the junction revealed dark spots, and a cross‐grid of dark lines, which could be correlated with the threading defects, and the dislocation network just below the surface, respectively. The SEM results showed that these defects had a deleterious effect on the luminescent and electrical properties of the material in the vicinity of the p‐n junction, and would therefore impair the performance of devices made from these layer structures.
Use of differential interference contrast microscopy to determine cell renewal times in mouse intestine
Authors: Smith M. W. , Jarvis L. G. 
Published: August 2011

SUMMARYPieces of mouse mid jejunum have been cleared in glycerin and examined by differential interference contrast microscopy at low powers of magnification. The position and number of crypts and villi can be determined in the same specimen using this technique. The calculated value for crypt/villus ratio 4·53 ± 0·99 (mean ± SD) is less than a previously published value obtained using indirect techniques. A revised estimate of cell renewal time, based on this newly determined value for crypt/villus ratio, is 45 h. This agrees with earlier estimates derived from entirely different methods of analysis. The general usefulness of this form of light microscopy in helping one appreciate some three‐dimensional problems in mucosal architecture is emphasized.
A critical examination of the electron‐microscopical evidence for swollen hydrated cellulose fibrils in green plants
Authors: Willison J. H. M. , Brown R. M. , Mueller S. C. 
Published: August 2011

SUMMARYThe electron‐microscopical evidence for the existence of ‘nascent cellulose fibrils in green plants’ (Leppard, G.G. & Colvin, J.R., J. Microsc. 113 (1978), 181) is examined critically. It is concluded that images of pre‐shadowed carbon replicas which appear to show cell wall microfibrils having a sheath enclosing a core are unavoidable technical artefacts in which the sheath consists of the replicating carbon. This interpretation is supported by the finding of similar apparent sheaths around air‐dried microfibrils which were suspended above the main plane of the substrate surface at the time of replica‐making. It is shown that the impressions of microfibrils in fractured plasma membranes have greater cross‐sectional dimensions than the microfibrils themselves as a result of the relationship between the microfibrils and the plasma membrane, and that such impressions are not evidence of ‘nascent fibrils’. Furthermore, it is argued that there is no evidence at present which supports the hypothesis that a swollen, sheathed ‘nascent fibril’ of cellulose is produced by prokaryotic Acetobacter xylinum. A light core is demonstrated in images of unshadowed replicas of microfibrils and it is proposed that radiation damage may play a rôle in the formation of this image. It is demonstrated that the coincidence of Fresnel fringes around unshadowed defocused replicas of microfibrils can also lead to the formation of an apparent core. Problems associated with obtaining measurements from replicas of cell wall microfibrils are discussed and some recommendations are made.
Interactions of uranyl ions with lipid bilayer membranes
Authors: Ting‐Beall H. P. 
Published: August 2011

SUMMARYUranyl ions (UO22+), once bound to the phosphate moieties of phospholipid head groups, stabilize bimolecular lipid membranes (BLMs) as well as decrease the nonactin‐induced membrane conductance. UO22+ bind to a phosphatidyl choline‐cholesterol (2:1, molar ratio) BLM surface with a dissociation constant of 2·3 μM and a maximum change in surface potential of 88 mV, which corresponds approximately to one uranyl ion per 31 nm2 surface area. Furthermore, uranyl ions can penetrate the lipid bilayers as neutral complexes such as uranyl acetate.
Nonradiative recombination at dislocations in III–V compound semiconductors
Authors: Petroff P. M. , Logan R. A. , Savage A. 
Published: August 2011

SUMMARYCarrier recombination at individual dislocations is investigated for the case of misfit dislocations at a heterojunction between Ga1–xAlxAs1–yPy epitaxial layers. Through the combined use of scanning transmission electron microscopy, electron beam induced current and cathodoluminescence analysis, it is shown that the non‐radiative and radiative recombination properties of dislocations are associated with their fine crystallographic configuration. The edge Lomer‐Cottrell dislocation is found to be electrically neutral. The absence of carrier recombination strongly suggests that core reconstruction may be important in eliminating dangling bonds and kink sites along the core of these dislocations. An undissociated dislocation with a Burgers vector b=1/2a〈110〉 is proposed as the more likely configuration for the edge Lomer‐Cottrell dislocation. An asymmetry in the nonradiative recombination properties and crystallographic structure of the 60° dislocation is also reported and discussed.
Observation of dislocations and microplasma sites in semiconductors by direct correlations of STEBIC, STEM and ELS
Authors: Fathy D. , Sparrow T. G. , Valdrè U. 
Published: August 2011

SUMMARYA high voltage electron microscope, equipped with scanning transmission (STEM) attachment, electron beam induced conductivity (EBIC) facilities, and electron energy loss spectrometer (ELS), has been used to investigate semiconductor devices. The capability of STEM to produce, simultaneously or sequentially, conductive and transmission images of the same specimen region, which can also be ELS analysed, is exploited in order to establish direct and unambiguous correlations between EBIC and STEM images of defective regions (dislocations and microplasma sites) in silicon devices.The results obtained are discussed in terms of correlations, resolution, contrast, and radiation damage; in addition, a comparison is made between this method and the other correlation methods based on EBIC/SEM (scanning electron microscope) and TEM (transmission electron microscope).
Minority carrier lifetime mapping in the SEM
Authors: Steckenborn A. 
Published: August 2011

SUMMARYA method is described for obtaining two‐dimensional distributions of minority carrier lifetimes in semiconductor materials for optoelectronic applications. The novel features of the system are: on line analogue calculation of the lifetime from the decay of the cathodoluminescence signal after switching off the SEM electron beam; simultaneous computerized mapping of the signals obtained in this manner in the scanning electron microscope. Typically, it permits establishing a map of 1 mm2 with 512 times 512 data points in 10 min for lifetimes down to 3 ns.
EBIC microscopy of double‐heterostructure laser materials and devices
Authors: Stevenson J. L. , Skeats A. P. , Heckingbottom R. 
Published: August 2011

SUMMARYThe electron beam induced current (EBIC) mode of the scanning electron microscope (SEM) has been used to characterize double heterostructure laser materials and devices in GaAs/Ga1–xAlxAs. Scanning the electron probe across the cleaved face of the laser structure shows that displacement of the p‐n junction with respect to the heterojunctions is not uncommon with displacements ∼ 1 μm occurring. Concurrent measurement of the minority carrier diffusion length gives very short lengths of 0·3–0·4 μm, differing from those in much thicker layers. Scanning the electron probe in the contact plane indicates clearly that long‐lived lasers exhibit marked heterogeneity during degradation. Considerable complexity and variation is recorded depending upon the fabrication details and degradation conditions adopted.
SEM and TEM observations of emitter‐collector pipes in bipolar transistors
Authors: Gowers J. P. , Bull C. J. , Ashburn P. 
Published: August 2011

SUMMARYThe EBIC mode of the SEM has been used to identify the sites of emitter—collector pipes in diffused npn bipolar transistors. After thinning, the same devices were studied in the TEM at 1 MV. A one‐to‐one correlation was found between the sites of the pipes and the arms of complex dislocations originating from the emitter diffusion‐induced dislocation network and looping down into the collector. The white EBIC contrast at pipes was often accompanied by adjacent black contrast due to the recombination of electrons at parts of the dislocation in the base region.
SEM and TEM studies of defects in Si‐doped GaAs substrate material before and after Zn diffusion
Authors: Darby D. B. , Augustus P. D. , Booker G. R. , Stirland D. J. 
Published: August 2011

SUMMARYSi‐doped GaAs slices after Zn diffusion exhibited a marked decrease in luminous efficiency and a large increase in p‐n junction depth when the initial carrier concentration due to the Si was > 3·5 times 1024 m−3. SEM studies using the CL and EBIC methods, and TEM examinations using plan‐view and cross‐section specimens, showed that these behaviours were associated with high densities of structural defects, interpreted as Zn precipitation. Reasons for these behaviours in terms of nucleation behaviour and diffusion mechanisms are suggested.
X‐ray topography of large single crystals
Authors: Dineen C. , Jones F. J. , Isherwood B. J. , Wallace C. A. 
Published: August 2011

SUMMARYA requirement exists in the fabrication of certain electronic devices for non‐destructive examinations of the structural perfection of large single crystals. Two X‐ray topographical techniques which fulfill this requirement are described.A curved crystal transmission topography technique provides images of equivalent definition to those obtained by Lang topography, but with a very large gain in speed. This technique is restricted to the examination of flexible plates of uniform thickness and is particularly suited to silicon slices.A topographical method, incorporating an unorthodox scanning mode, has been applied to the assessment of the surface perfection of long crystals. Using this technique, crystals up to 205 mm in length have been examined on a suitably modified Lang camera of limited traverse capability.
Measurement of radiation damage by electron energy‐loss spectroscopy
Authors: Egerton R. F. 
Published: August 2011

SUMMARYInner shell ionization edges in the energy‐loss spectrum were used to measure the loss of gaseous elements from thin samples of nitrocellulose, polyvinyl formal, copper phthalocyanine, graphite bisulphate and sodium chloride during exposure to 80 keV electrons. The irradiation kinetics were measured for electron doses up to 104 C m−2 and for dose rates up to 10 mA m−2. The energy‐loss technique is discussed in relation to other methods for assessing radiation damage.
Improved handling of structural fragile cell‐biological specimens during electron microscopic preparation by the exchange method
Authors: Peters Klaus‐Rüdiger 
Published: August 2011

SUMMARYAn exact method of preparation of soft biological specimens for electron microscopic analysis of surface fine structures is described. It allows routine preparations of fragile specimens for SEM and TEM imaging modes. With this procedure physical preparation parameters such as mechanical loads on the specimen surface or changes of temperature are controlled. The wet specimens are premounted in cheap disposable BEEM‐containers or glass boats and are constantly kept under liquid in a closed system. The exchange of preparation media is performed continuously and, if necessary, over gradients. For comparative investigations with different EM‐modes, at each step of the procedure parts of the specimens may be removed for individual processing. Conventionally prepared critical‐point dried specimens are compared to those processed by the exchange technique and preservation of surface fine structures is demonstrated. Shadow‐casted clathrin cages and stereo‐replicas of virus infected cell cultures are shown in TEM preparations. For SEM, coverslip cell cultures and isolated glomerulus basement membranes are prepared and an additional flat embedding for TEM ultrathin sections is demonstrated.