bluuebunny/crossref_metadata_2025 huggingface dataset:
Observation of transmission electron sputtering at 100 and 120 kV
Authors: Bradley Charles R. , Zaluzec Nestor J.
Published: June 2020

Calculations indicate that baring contamination problems it should be possible to observe transmission electron sputtering of some materials at 120kV. Figure 1 shows a plot of the calculated total Mott cross-section for zinc. The calculation shown includes an estimate of the enhancement expected due to collision cascades in the bulk of the sample. The higher curve assumes a surface binding energy equal to the sublimation energy of zinc; the lower curve assumes a surface binding energy equal to twice the sublimation energy. The actual surface binding energy is unknown, but is expected to lie between these two limits. At 120kV, then, the cross- section should be between 3033 bams and 717 barns. It should be possible to observe sputtering of a material with such a high cross-section. Chems has observed sputtering of gold films and has measured cross-sections from approximately 300 bams to 2200 bams. Since gold surfaces are singularly clean it is expected that observation of sputtering in zinc will be more difficult.
Design and initial performance of a UHV-HREM
Authors: Marks L. D. , Kubozoe M. , Tomita M. , Ukiana M. , Furutsu T. , Matsui T.
Published: June 2020

We report here on the basic design and the initial performance of a fully bakeable UHV-HREM. The instrument, see Figure 1,is based upon a conventional H-9000 electron microscope with the natural differential pumping of the column separating the standard gun and photographic chambers from the UHV specimen chamber. The addition of small ion pumps at the condenser aperture, the selected area aperture and between the two projector lenses (see Figure 2) (which attain operational pressures of ∼2 X 10-8, ∼2 X 10-8 and ∼2 X 10-7 Torr respectively) assist this differential pumping. To achieve full UHV performance the specimen region is bakeable to 200°C using a combination of tape and band heaters and quartz-halogen lamps. Specimens for HREM analysis can be pretreated in the transfer chamber which is shown in Figure 3. The specimens, held in a detachable side entry cartridge, can be moved both back and forward and rotated by 360° to face ports onto which equipment for LEED, ion beam, X-ray, evaporation and dye laser treatment of surfaces will be mounted; the transfer chamber acts as a conventional multi-port surface science chamber.
Identification of dislocations on crystal surfaces
Authors: Peng L.-M. , Cowley J.M. , Hsu Tung
Published: June 2020

A dislocation, when meeting an external crystal surface, will result in the re-arrangement of surface atoms because of the strain field associated with it. For a free surface further complication comes from the requirement that no forces can act on the surface. The displacement field is then a superposition of the displacement field from the dislocation in an infinite crystal and from the surface stress relaxation that cancels the stress field from the dislocation on the surface. The general case for a straight dislocation of arbitrary Burgers vector and arbitrary emerging angle in a semi-infinite, elastically isotopic medium has been solved by Yoffe, and this general solution has been used in our calculations.

In the technique of reflection electron microscopy (REM) an electron beam is incident on the surface. The reflection electron imaging is extremely sensitive to any deviation from a perfect surface, and therefore provides a ideal method of observing the surface dislocations.
TEM/STEM characterization of industrial type supported Pd catalysts: Effect of an in situ hydrogen activation
Authors: Szymanski R. , Lynch J.
Published: June 2020

TEM is routinely used to control the metallic dispersion of industrial supported metal catalysts, since in complement to the chemisorptive methods it provides unique local information about particle size distribution, i.e. about the quality of the metal dispersion. An evaluation by TEM of the mean particle size can be useful to quantify the metal dispersion assuming a simple model for the particle shape, e.g. spherical or cubic. However, except for the cases where chemisorption fails (e.g. poisonning), this evaluation is mainly considered as a mean of checking the representativity of the statistical distribution of local information in comparison with chemisorption results. Discrepancies are often observed between the two techniques and many reasons can be advanced for these such as statistics, particle shape models, electron beam induced changes, chemisorption assumptions (cf coverage), etc... In fact, we consider that in a number of cases one of the primary limitations is likely to be due to the in situ problem in TEM, which is inherent to most techniques involving an ex situ characterization.
Electron microscopy of a rigid-rod/nylon thermoplastic molecular composite physical blend
Authors: Lloyd P. , Omlor R. , Vezie D. , Krause S. J. , Kumar S. , Adams W.W.
Published: June 2020

“Molecular composites” are a new class of structural polymers which are high-strength, high-modulus, thermally stable, and environmentally resistant. A rigid-rod, extended chain polymer component is used to reinforce a matrix of a ductile polymer with the intent of achieving a composite on the molecular level. The critical factor in processing a “molecular composites” is that the rigid-rod reinforcing component be well dispersed and not phase separate from the matrix component at any stage of processing. For the greatest versatility, a “molecular composites” system should be amenable to fabrication with traditional thermoplastic processing techniques. We previously reported on the morphology of “molecular composites” formed by coagulation spinning from a solution of rigid-rod/stiff-coil polymer blend and from a solution of a rigid-rod/stiff-coil triblock copolymer. Although these polymer systems formed “molecular composites”, they did not have a glass transition temperature below the degradation temperature and could not be consolidated by thermal processing techniques. In this paper we are reporting on the morphology of rigid-rod and flexible-coil thermoplastic blends which are processable by precipitation and thermal consolidation.
Interfaces and substructures in copper-based shape memory alloys
Authors: Perkins Jeff , Wu M. H. , Adachi K.
Published: June 2020

The delineation of interfaces and substructures by conventional transmission electron microscopy is reviewed for three different transformations of interest in copper-based shape memory alloys.

The first case considers the interfacial structure of martensite plate boundaries in a Cu-14.6Zn-16.1Al (atomic %) alloy. The detailed structure of such interfaces is important to their relative mobility in shape memory alloys. One-dimensional lattice images such as seen in Fig. 1 help to model the effect of substructural features in the martensite on the atomistic structure and so the mobility of such boundaries1. In the example shown, the presence of very thin structural faults with a 2H structure are detected within an otherwise 18R martensite plate.

The second case describes the interaction of the state of parent phase order with the structure of bainite plates formed upon isothermal aging at 150-350 C in a Cu-27Zn-4Al (weight %) alloy . Two types of atomic ordering occur in the parent phase and tend to be inherited by the bainite transformation product.
Examination of CaO-Dy2O3 for potential use as a high-temperature transformation toughening System
Authors: Fleming M. M. , Kriven W. M.
Published: June 2020

Similarities exist between the tetragonal to monoclinic transformation of ZrO2 and the monoclinic (B) to cubic (C) transformation of Dy2O3. On cooling the transformation occurs at 1950°C and is accompanied by an 8 % volume increase which causes shattering of bulk specimens. The transformation can be suppressed, however, by minor additions of CaO. An attempt was made to fabricate a “PSD” analogue to partially stabilized zirconia (PSZ).

As-received and chemically precipitated powders of pure Dy2O3 were mixed with CaO (0 to 25 mol%), uniaxially and cold isostatically pressed, sealed in small Mo crucibles and sintered at various temperatures (1900° or 1650°C) and times before cooling or subsequent annealing treatments. Some pellets were annealed in the two phase (B + C) region at 1700°C for 2 hours before quenching. Specimens were examined by XRD, TEM, EDS, HVEM, and STEM.

A fast quenching in combination with the =8 mol% CaO additions were found to be essential for retention of the high temperature B phase down to room temperature.
Intermetallic contacts to gallium arsenide: Doping and alloying by limited solid-phase reactions
Authors: Sands T.
Published: June 2020

Further advances in the miniaturization and integration of GaAs-based electronic and photonic devices necessitate the development of low-resistance (ohmic) and rectifying (Schottky) contacts that are thermally stable and morphologically uniform. In principle, optimum stability and morphology can be achieved by codepositing intermetallic phases (e.g. NiGa, CoGa and AuGa2) that are known to be in thermodynamic equilibrium with GaAs at the relevant temperatures. Such an approach must, however, be combined with a mechanism by which the GaAs may be doped or alloyed to yield contacts with a range of electrical properties (e.g. low-barrier ohmic, tunneling ohmic or high-barrier Schottky contacts). In this paper, the fabrication of stable and uniform ohmic and Schottky contacts using limited reactions between GaAs and intermetallic phases that contain the doping (e.g. Ge or Si) or alloying (e.g. Al or In) element is described. The fact that these reactions are limited - involving only 5-10 nm of GaAs at the metallization/GaAs interface - makes TEM an essential tool for characterizing these contacts.
Digital restoration of ADF-STEM images
Authors: Kirkland Earl J.
Published: June 2020

Frieden and Wells have derived a maximum likelihood (ML) image restoration algorithm that accurately models the noise in each image element using Poisson counting statistics. This method also leads naturally to “maximum entropy” like ideas. They have reported a rather dramatic resolution enhancement when this method was applied to low light level astronomical images in which the image noise was essentially due to photon counting statistics. This low light level situation also accurately models the ADF (annular dark field) STEM (scanning transmission microscope) image if the image is aquired digitally by electronically counting the individual scattered electrons for each position of the focused probe.

The simplest ADF-STEM image model assumes that the electron intensity distribution in the focused probe is the incoherent point spread function (psf) of the image.

where g(x)=recorded image, f(x)=ideal image, n(x)=random noise, * represents convolution and
The maximum-likelihood method for EM autoradiography: Evaluation and comparison to cross-fire-analysis
Authors: Roysam Badrinath
Published: June 2020

Electron microscopic autoradiography is of growing importance as a technique for the quantification of radiolabelled biochemicals in subcellular structures. In this paper, we present the results of a series of experiments that evaluate the Maximum-Likelihood (ML) method of Miller et al. and compare its performance with the well-known crossfire (CF) method.

We used the ML and CF methods to analyze a common set of 48 different simulated micrographs (Fig.1) at 5 different grain-counts and 3 different Half-Distances (HDs) for a point-spread modelling H. The CF method was implemented ideally to correspond to the use of an uncountably infinite number of mask points. The count-levels and HDs were chosen to span the range of realistic values. The experiments were repeated a large number of times and the ensemble signal-to-noise ratio (ESNR), measured in decibels (dB) was computed and used as an average performance measure. A 3dB performance improvement in ESNR amounts to a doubling of accuracy.
Digital image processing methods applied to the study of annealing time on semiconductor-metal eutectic composites
Authors: Hefter J.
Published: June 2020

Semiconductor-metal composites, formed by the eutectic solidification of silicon and a metal silicide have been under investigation for some time for a number of electronic device applications. This composite system is comprised of a silicon matrix containing extended metal-silicide rod-shaped structures aligned in parallel throughout the material. The average diameter of such a rod in a typical system is about 1 μm. Thus, characterization of the rod morphology by electron microscope methods is necessitated.

The types of morphometric information that may be obtained from such microscopic studies coupled with image processing are (i) the area fraction of rods in the matrix, (ii) the average rod diameter, (iii) an average circularity (roundness), and (iv) the number density (Nd;rods/cm2). To acquire electron images of these materials, a digital image processing system (Tracor Northern 5500/5600) attached to a JEOL JXA-840 analytical SEM has been used.
On the characterization of superstructures in HREM images of YBa2Cu3O7-x using image processing techniques
Authors: Pérez-Ramírez J.G. , Pérez R. , José-Yacamán M.
Published: June 2020

Electron diffraction patterns obtained from samples of YBa2Cu3O7-x (0≤x≤1) compound shows besides the normal tetragonal or orthorhombic structures also superstructure reflections corresponding to various diffuse scattering effects which are attributed to the ordering of the oxigen vacancies existing in the samples. The diffuse scattering was not always the same in appearance. It was often not localized at position but appeared as lines with uniform intensity connecting neighbouring diffraction spots. Optical diffraction patterns from HREM images of this compound have indicated the presence of a superstructure with a period equal to the double periodicity obtained under [001] zone axis diffraction conditions. In this work we studied HREM images of twin and matrix crystals adjacent to the commonly found (110) twin boundaries in the superconducting compound. Image processing techniques have been applied to these images and the results indicate also the presence of a superstructure which can clearly be seen in the enhanced processed images.
A transmission electron microscopic study of ceramic superconducting thin films prepared by laser deposition
Authors: Hwang D. M. , Nazar L. , Wu X. D. , Inam A. , Venkatesan T.
Published: June 2020

Many applications of the new high temperature ceramic superconductors require the materials to be prepared in a thin film form. The substrates play an essential role in the superconducting properties of these films. In order to optimize the critical temperatures and currents of the films and to search for new suitable substrates of desirable properties, it is important to understand the interfacial interaction between the films and the substrates. TEM studies of the cross-sectioned specimens are indispensable in providing such information.

In this paper, we describe the microscopic structures of two types of Y-Ba-Cu-O thin films deposited on SrTiO3 substrates with a KrF excimer laser. The high-temperature-processed specimens are deposited at 450 C in vacuum and post-annealed for 1 hr at 900 C in an oxygen atmosphere. The low-temperature-processed specimens are deposited at 650 C in an oxygen pressure of 5 mTorr, and post-annealed for 3 hr at 450 C in an oxygen atmosphere.
Composition variations near grain boundaries in YBa2Cu3O7-δ
Authors: Babcock S.E. , Kelly T.F. , Larbalestier D.C.
Published: June 2020

Detailed electromagnetic characterization of samples of YBa2Cu3O7-δ (123) have shown this material, at least in its sintered form, is composed of islands of good superconductor which are separated from one another by “weak links” consisting of regions of poor superconductor or normal material. A number of researchers have suggested that these weak links are associated with grain boundaries. Therefore, conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDAX) have been used to investigate the morphology, crystallography, and composition of typical grain boundaries in this material.

The electromagnetic properties of the specific samples from which the TEM specimens were prepared had been studied in detail. Briefly, these samples possessed relatively low normal state resistivities and nearly field independent transport critical current densities, indicating that they were of relatively high quality.

For these initial studies, specimens for TEM and STEM/EDAX were prepared by dimpling plus ion milling (3-4kV, 0.5mA per gun, liquid nitrogen cooled stage).
Microstructure of polycrystalline silicon implanted with As ions at high and low temperatures
Authors: Cole Melanie W. , Shih Yih-Cheng , Cook Charles F.
Published: June 2020

Ion implantation is an important process for doping polycrystalline silicon layers during IC device fabrication. The use of higher beam currents is desirable from the process point of view to achieve shorter implant times. An important consideration of using Increased beam current, with its resultant higher implant temperature, is the effects on the layer's electrical properties and microstructures. In order to better understand this phenomenon two sets of samples implanted at room temperature and 400°C were investigated by transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS) and spreading resistance analysis (SEA). Both sets were implanted at 190 KeV with an As ion dose of 2 x 1016/cm2 into a 220 nm thick polycrystalline silicon layer overlying an oxide layer on a Si wafer substrate. These sample were then annealed at 975°C for 1 hr in a nitrogen atmosphere.
Defect generation and propagation in GaAs solar cells
Authors: Jones K.M. , Matson R.J. , Al-Jassim M.M. , Vernon S.M.
Published: June 2020

It is well known that dislocations have deleterious effects on the performance of minority carrier semiconductor devices. In a previous study(1), the results of an EBIC examination of GaAsP wide bandgap solar cells was reported. The effects of defects in the 106-108 cm-2 range on various cell parameters were investigated. However, the equally important 104-106 range was not studied. In this work, we report a study on defects in low bandgap (1.4 eV) GaAs cells in the 104-108 cm-2 range. These cells were grown by low pressure MOCVD on GaAs substrates. In order to introduce dislocations with such a wide range of densities, an intermediate mismatched layer of GaAs1_xPx was introduced into the structure (Fig. 1). Five different device-type structures were grown in which the P concentration (x) was varied from 2% to 32%. These concentrations correspond to a lattice mismatch of 7.3x10-4 and 1.2xl0-2respectively. As expected, the higher the P concentration the larger the mismatch being introduced into the system and therefore, the higher the defect density.
SEM mounts coated with evaporated carbon
Authors: Stoner John O.
Published: June 2020

In x-ray studies, interferences from metallic components in SEM mounts are usually avoided by use of carbon mounts or coverings on aluminum mounts. Carbon planchets, beryllium planchets and carbon paints are used as such coverings.

Such methods for avoiding x-ray characteristic lines have disadvantages: Carbon mounts are fragile and slippery. Planchets and paint represent additional handling; paints introduce volatiles into the microscope.

We have tested evaporated carbon coatings on aluminum specimen mounts in an attempt to remove these difficulties. Spectrographically pure graphite was evaporated onto cleaned aluminum specimen mounts. Several different carbon thicknesses were tested for efficacy in reducing the aluminum K x-ray emission.

The best results were obtained with coatings having thickness of at least 5 micrometers (Fig. 1). Simple calculations verified that this thickness was sufficient to stop completely the electron beam at 20 keV. Spectra of coated mounts showed primarily a slowly varying bremsstrahlung background.
In situ microprobe quantitation of inorganic particle burden in paraffin sections of lung tissue
Authors: Abraham Jerrold L.
Published: June 2020

Inorganic particulate material of diverse types is present in the ambient and occupational environment, and exposure to such materials is a well recognized cause of some lung disease. To investigate the interaction of inhaled inorganic particulates with the lung it is necessary to obtain quantitative information on the particulate burden of lung tissue in a wide variety of situations. The vast majority of diagnostic and experimental tissue samples (biopsies and autopsies) are fixed with formaldehyde solutions, dehydrated with organic solvents and embedded in paraffin wax. Over the past 16 years, I have attempted to obtain maximal analytical use of such tissue with minimal preparative steps. Unique diagnostic and research data result from both qualitative and quantitative analyses of sections. Most of the data has been related to inhaled inorganic particulates in lungs, but the basic methods are applicable to any tissues. The preparations are primarily designed for SEM use, but they are stable for storage and transport to other laboratories and several other instruments (e.g., for SIMS techniques).
Scanning tip microscopies: An overview and some history
Authors: Clayton Teague E.
Published: June 2020

The generic concept of scanned tip microscopy is much the same as the conventional scanning electron microscope. Both provide a one-to-one mapping between a point sampling of some physical property of a probe-sample surface interaction and a corresponding point in an image. Correspondence between points on the sample surface and image points is achieved by synchronizing the image generation process with probe motion. Probe motion is generally in a rastered or boustrophedon path over a selected area of the sample (Fig.1). A very lucid description of this generic microscope concept is given in a paper by Matey and Blanc. The major differences with tip microscopy methods are that no lenses are used, probe motion relative to the specimen is produced mechanically, and the probe is a solid material.

Although the roots of scanned tip microscopy extend back almost twenty years to the work of Williamson with diamond styli and Young et al.
Some instrumental aspects of single atom microscopy
Authors: Kopf D. , Utlaut M. , Crewe A.V. , Isaacson M. , Mankawich W.
Published: June 2020

We have indicated in previous publications that a scanning transmission electron microscope (STEM) capable of atomic resolution may be a useful instrument for surface science studies and, in particular, capable of observing the distribution and diffusion of single heavy atoms on thin film substrates (1-3). In our previous work, we have used a microscope which was primarily oriented towards biological work and had a very simple optical system (only an electron gun plus an objective lens (4)). This limited the flexibility with which optical conditions would be changed. Moreover, the stringent requirements for atom imaging were not necessarily compatible for routine biological electron microscopy. Thus, we decided to shift our physical experiments in atom microscopy to another, more versatile instrument.

This instrument is a modified version of a 100 keV STEM which has been described before (5). The basic system is indicated schematically in figure 1. It consists of a 3 cm Butler gun followed by a condensor lens, an objective lens and a projector lens (or in recent parlance, a “post specimen” lens).
Crossed lenses for electron-microscopic devices
Authors: Baranova L.A. , Petrov I.A. , Yavor S.Ya.
Published: June 2020

Efforts directed towards perfecting the contemporary electron-microscopic devices require improvements in quality of focusing elements, creation of high-parameter lenses, together with tendency to greater simplicity in design. One of possible solutions of this problem is the employment of electrostatic crossed lenses giving high-quality image and possessing high production effectiveness /1,2/. The electrodes of this lens consist of flat plates with apertures. The apertures are oblong in shape, e.g. rectangular. The electrodes are aligned along the optical axis, with the apertures of the adjacent electrodes positioned at 90° to each other.

Fig. 1 shows a single crossed lens. Such a lens is astigmatic, it converges charged particles in one direction and diverges them in the perpendicular direction. If the middle-electrode potential is lower than the potential of the extreme electrodes, then the lens converges electrons in the direction of elongation of the apertures of the extreme electrodes. With change in polarity of the electrodes, the converging and diverging planes exchange places.
Electron optical experiments with a magnetic imaging filter
Authors: Krahl D. , Herrmann K.-H. , Kumath W.
Published: June 2020

In the CTEM, imaging filter systems consisting of several magnetic prisms permit the removal of inelastically scattered electrons. Such systems transfer the diffraction plane and the intermediate image stigmatically. A prerequisite for a singly achromatic imaging is that the filter produces a radial intermediate image in its plane of symmetry.

The symmetry relations of the magnetic fields and the electron paths permit correction of the second-order distortion and of the second-order aperture aberration [1]. The aperture-dependent magnifications, however, remain uncompensated. These aberrations must be tolerated for filter systems which have stigmatic intermediate images [2], If, however, line foci exist between the prisms, hexapoles can be applied for correction (Fig. 1 [3,4]). Such corrections seem imperative in filters which are used for high resolution electron microscopy.

The adjustment of a symmetric optical path in our filter system by means of quadrupoles can be controlled by inserting an edge into the symmetry plane and simultaneously observing the image produced by the filter.
Detection efficiency and estimation of the performance of high voltage STEM
Authors: Ishikawa A. , Morita C. , Hibino M. , Maruse S.
Published: June 2020

One of the problems which are met in conventional transmission electron microscopy (CTEM) at high voltages is the reduction of the sensitivity of photographic films for high energy electron beams, resulting in the necessity of using high beam current. This cancels out an advantage of high voltage electron microscopy which is otherwise expected from the reduction of the inelastic scattering in the specimen, that is the reduced radiation damage of the specimen during observations. However, it is expected that the efficiency of the detector of scanning transmission electron microscopy (STEM) can be superior to that of CTEM, since the divergence of the electron beam in the detecting material does not affect the quality of the image. In addition to observation with less radiation damage, high voltage STEM with high detection efficiency is very attractive for observations of weak contrast objects since the enhancement of the contrast (which is an important advantage of STEM) is easily realized electrically.
Electron exposure-dependent contrast transfer
Authors: Chiu Wah , Glaeser Robert M.
Published: June 2020

The use of electron microscope images for high resolution biological structure analysis has the important advantage that the structural phase information, which is not easily obtained in x-ray or electron diffraction studies, may be easily obtained from images by suitable numerical computations. It has been shown that the phase error determined from image data is much smaller than that which is generally achieved in the use of the isomorphous replacement method in protein x-ray crystallography (1). Due to the constraints imposed by electron radiation damage in the specimen, however, it is quite difficult to obtain high resolution image data for most biological specimens. The use of low-dose image recording techniques, and subsequent computer averaging, has made it possible to obtain 7 Å resolution images of a crystalline specimen embedded in glucose (1). The limitation at this resolution could be caused by instrumental factors and/or poor signal transfer in the recording medium when it is exposed to only a small number of electrons.
The DQE of an electron image recording system
Authors: Herrmann K.-H. , Krahl D. , Rust H.-P
Published: June 2020

The high detection quantum efficiency (DQE) is the main requirement for an imagerecording system used in electron microscopy of radiation-sensitive specimens. An electronic TV system of the type shown in Fig. 1 fulfills these conditions and can be used for either analog or digital image storage and processing [1], Several sources of noise may reduce the DQE, and therefore a careful selection of various elements is imperative.

The noise of target and of video amplifier can be neglected when the converter stages produce sufficient target electrons per incident primary electron. The required gain depends on the type of the tube and also on the type of the signal processing chosen. For EBS tubes, for example, it exceeds 10. The ideal case, in which all impinging electrons create uniform charge peaks at the target, is not obtainable for several reasons, and these will be discussed as they relate to a system with a scintillator, fiber-optic and photo-cathode combination as the first stage.
Electron microscopy of nuclear etch tracks in solids
Authors: Vuković J. , Antanasijević R. , Todorović Ž.
Published: June 2020

A little over a ten years since the track etch method for ionizing particles in dielectric solids was introduced by R.Fleischer, P. Price and R.Walker (1,2). Some our results was presented at 2nd Balkan Congress on Electron Microscopy (3).

In this communication we have investigated solid state nuclear track detectors (SSNTD): cellulose nitrate-CN (domestic product), polycarbonate-PC (“Makrofol”) and crystals of mineral auripigment (As2S3) in order of alpha and fission tracks dating.

In CN and PC film a charged particle leaves a radiation damage-a latent track which is etched with H2O solution of NaOH in order to be visualized. For detailed analysis of such a track-etch pit we have used TEM for CN layers 3-4 microns thick and direct observation at 80-100kV (Fig.l). Tracks may be well shown also by the usual replication technique (Fig.2). The whole interior of the etched alpha track as well as the transparent carbon shell, is well recognized.
SEM and TEM investigation of VPE layer structure for Gap light emitting diodes
Authors: Darby D.B. , Palolil J. , Booker G.R.
Published: June 2020

A basic problem associated with the fabrication of GaP LEDs is the high dislocation density present in GaP VPE layers grown on GaP LEC substrates, which is detrimental to device performance. Most of the layer dislocations originate from loops present in the substrate that intersect the substrate surface when growth commences. This paper is concerned with an experiment designed to reduce the dislocation density in the layer by deliberately introducing lattice strains during the growth.

An experimental structure was prepared comprising a substrate cut 10° off the [100] axis, onto which was grown a layer 17μm thick doped with 2 × 1019 cm-3 of N atoms, followed by a layer 30μm thick undoped. The N causes a crystallographic mismatch at the two interfaces, and it was anticipated that some of the dislocations propagating through the first layer would bend around so as to lie along the second interface.
Interface structure and Schottky barrier height of silicade-silicon contact
Authors: Tu K.N. , Ohdomari I. , Libertini S.H.
Published: June 2020

At present most rectifying contacts in integrated Si devices are made of transition metal silicides such as Pd2Si and PtSi. The electrical potential difference across a metal to semiconductor rectifying contact is called Schottky barrier. While many theories and studies have been devoted to increase our understanding of the origin and details of Schottky barrier, we find very little effort has been given to correlate the electrical barrier and the metal-semiconductor interface structure. We expect that there exists such a structure-property correlation and we report here our preliminary finding of the correlation in Pd2 Si contacts to n-type Si.

Silicon wafers used here were n-type, 10 to 20 Ω-cm, both (111) and (001) oriented, 1 or 1 1/4" in diameter, and HF-etched before Pd deposition. For the structural study, a 800ÅPd film was e-beam evaporated in a vacuum of 10-7 torr onto the Si kept at various substrate temperature, Ts, shown in Table I
Electron micro-densitometry during in-situ TEM investigations
Authors: Heinemann Klaus , Poppa Helmut
Published: June 2020

An electron detector with small detection area for use in the final image plane of a transmission electron microscope has been commercially offered by TEM manufacturers (1). However, little has been reported about the application of such a device. In this report, the construction principle and the operation of a novel microdensitometry device is described which combines precision image point selection with versatility, high sensitivity, ease of operation, and comparatively low cost.

The electron microdensitometer system consists of a transparent phosphor screen onto which the electron image is projected, a small “channeltron” electron multiplier (supplied by Galileo/Bendix) underneath, and a closed-circuit TV system (Fig.l). The screen has an effective diameter of 45 mm and contains a 2 mm concentric hole which allows a small beam of electrons to pass unobstructed to the electron multiplier. The multiplier consists of a 3 mm O.D. tube in custom L-shaped configuration and is mounted such that its collector is located outside the screen area to minimize obstruction of the image viewed on the TV monitor.
Interaction effects in direct electron beam lithography on silicon substrates
Authors: Phang J.C.H. , Ahmed H.
Published: June 2020

The problems associated with the direct exposure of resist-coated silicon substrates with electron beams have been studied. The scattering of electrons in the electron resist, from the substrate, and from topographical features such as steps on the substrate causes exposure at some distance from the beam's point of entry. Experiments have been carried out by drawing lines with a 0.5 μm diameter probe at 15keV beam energy on a silicon wafer coated with a 0.35 μm thick PMMA resist. Two adjacent lines were exposed in each experiment. The separation between lines was increased in steps of 0.2 μm until the lines were well separated. A constant incident dose of 4 × 10 -6C/mm2 was used and standard development conditions were maintained at 1 minute in a 3:1 solution of IPA:MIBK. Measured line and gap widths are shown as functions of the separation between adjacent lines in Fig.
Incoherent illumination method with conventional electron microscope
Authors: Nagata Fumio , Matsuda Tsuyoshi , Komoda Tsutomu , Hama Kiyoshi
Published: June 2020

When fine details of thin films are observed, the image are generally composed of both amplitude and phase contrast. The image resolution is sometimes limited by the granular background noise of supporting film which is due to the phase contrast effect by fairly coherent illumination(CI).

In the present work, incoherent illumination(ICI) method has been studied to avoid the phase contrast effect using a conventional electron microscope(Hitachi HU-12A).

The ICI method was made by enlarging the illumination angle(β) to be equivalent to the glancing angle(α=1.4x10-2 radians) of objective aperture. The large angle illumination was achieved by the strong excitation of an objective lens.

At first, the properties of phase contrast in ICI image were studied as functions of beam divergence angle and defocus using a carbon film. Both analytical and experimental investigations show that the granular noise in a phase contrast image decreases as β is increased from l×l0-4 to l×l0-2radians.
Atomic resolution from 500kv electron micrographs by computer image processing
Authors: Uyeda N. , Kirkland E. , Fujiyoshi Y. , Siegel B.
Published: June 2020

We have successfully applied the method suggested by P. Schiske (1) for optimally combining several micrographs of different defocus values (Δfβ) in the presence of additive noise. If c(k) represents the Fourier transform of tne ideal, unaberrated bright field image, and jβ(k) the transform of the real micrographs obtained at different defocus values, then the filter functions Qβ(k) that reduces

to a minimum, was shown (1) to be, within a common multiplicative factor,

The contrast transfer function (CTF) is where λ is the electron wavelength and Cs is the spherical aberration coefficient of the objective lens. η(k) is the noise to signal ratio in reciprocal space for unit CTF.

This procedure was applied to images of a tilted crystaline specimen of hexadecachloro- phtalocyanatocopper (II) taken on the Kyoto 500KV electron microscope (2).
Possible applications of fraunhofer holography in high resolution electron microscopy
Authors: Bonnet N. , Troyon M. , Gallion P.
Published: June 2020

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.

Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.

We show some applications of the method and results of preliminary tests.

Possible application to the study of cavities

Small voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.
A simple way for producing holographic filters suitable for image improvement
Authors: Herrmann K.-H. , Reuber E. , Schiske P.
Published: June 2020

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.

In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.

A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.
On a generalized view of holography in relation to the phase problem in electron microscopy
Authors: Lannes A.
Published: June 2020

Let xO = ϕ (ζ1, ζ2) the object wave function describing a given wave function in a given plane, and let x be its "projection" in the complex Hilbert space E corresponding to the (sampled) domain under consideration. Let U1,…, Uj, …, Up be unitary operators in E, and let J be the "intensity mapping" :

xk denotes the kth component of x (for simplicity, we assume that E is finite dimensional). The wave-retrieval (or wave-reconstruction) problem in holography is to solve simultaneous equations of the form :

where some components xk are known a priori. JoUj denotes the mapping involved in the formation of the hologram yj. for example, when Uj the is the operator involved in Fresnel's diffraction, yj. is said to be a Fresnel hologram. Likewise, when Uj corresponds to the Fourier transform, yj is said to be a Fourier-transform hologram.
Computer simulation of dark-field imaging as a tool for image interpretatin
Authors: Fertig J. , Rose H.
Published: June 2020

For very high-resolution imaging the dark-field mode is widely used in electron microscopy because it produces generally higher contrast than bright-field. The relation between image intensity and object potential is highly nonlinear for dark-field imaging. To allow for arbitrary objects, one can rewrite the expression for the image intensity in terms of the complex scattering amplitude of the object. In the case of dark-field imaging, the formula for image intensity will contain the square of the complex scattering amplitude. Consequently the image intensity of N atoms is the sum of the intensities of N single atom images plus the sum over the cross-terms (one for each pair of atoms) arising from partially coherent superposition of scattered waves emanating from different atoms. The mutual intensity can be positive or negative. Therefore, at a point between two adjacent atoms, the intensity may be lowered to such an extent that the atoms are resolved, even if their interatomic distance is smaller than the resolution limit of the microscope (“superresolution”).
Imaging and diffraction from localized defects and disorder in crystals
Authors: Cowley J.M. , Fields P M.
Published: June 2020

The atomic arrangements in local perturbations of a crystal structure may be investigated by studying the diffuse scattering in diffraction patterns. Alternatively, for isolated perturbations the atom arrangements may well be imaged directly by high resolution electron microscopy in the near future. For either approach, realistic estimates are necessary of the nature and magnitude of dynamical effects in diffuse scattering. For neither case can the commonly used assumption of the column approximation suffice and the kinematical approximation is rarely relevant.

Calculations of dynamical scattering amplitudes, for isolated defects can be made by use of an artificial super-lattice with one defect per superlattice unit cell and a multislice calculation with slice content varying in the propagation direction. Calculations of images and diffraction patterns for split interstitials in Au and A1, with and without lattice relaxation have been reported by Fields and Cowley. Figure 1 shows images and diffraction patterns calculated for a single [100] split interstitial in Au with no relaxation followed by various thicknesses of perfect crystals, with 1MeV electrons, Cs = 1.8mm and objective aperture radius uo = 0.45Å-1.
Lattice imaging and pore structure of β ferric oxyhydroxide
Authors: Baird T. , Fryer J.R. , Galbraith S.T.
Published: June 2020

Introduction Previously we had suggested (l) that the striations observed in the pod shaped crystals of β FeOOH were an artefact of imaging in the electron microscope. Contrary to this adsorption measurements on bulk material had indicated the presence of some porosity and Gallagher (2) had proposed a model structure - based on the hollandite structure - showing the hollandite rods forming the sides of 30Å pores running the length of the crystal. Low resolution electron microscopy by Watson (3) on sectioned crystals embedded in methylmethacrylate had tended to support the existence of such pores.

We have applied modern high resolution techniques to the bulk crystals and thin sections of them without confirming these earlier postulates

Experimental β FeOOH was prepared by room temperature hydrolysis of 0.01M solutions of FeCl3.6H2O, The precipitate was washed, dried in air, and embedded in Scandiplast resin. The sections were out on an LKB III Ultramicrotome to a thickness of about 500Å.
Analysis and lattice imaging of a transitional event on garnets
Authors: Laval J.Y.
Published: June 2020

The exsolution of magnetite from a substituted Yttrium Iron Garnet, containing an iron excess may lead to a transitional event. This event is characterized hy the formation of a transitional zone at the center of which the magnetite nucleates (Fig.1). Since there is a contrast between the matrix and these zones and since selected area diffraction does not show any difference between those zones and the matrix in the reciprocal lattice, it is of interest to analyze the structure of the transitional zones.

By using simultaneously different techniques in electron microscopy, (oscillating crystal method microdiffraction and X-ray microanalysis)one may resolve the ionic process corresponding to the transitional event and image this event subsequently by high resolution technique.
Lattice imaging of Pd2Si thin films
Authors: Kuan T.S. , Tu K.N.
Published: June 2020

Thin films of near-noble metal silicide such as Pd2Si and PtSi are now being used as rectifying and ohmic contacts in high performance Si devices. These silicides are made by depositing and annealing the metals on Si. The substrate temperature and orientation and the annealing condition can affect the microstructure of the silicide (1) and in turn change the electrical characteristics of the contact.This study attempts to show that detailed structural information about thin Pd2Si films can be obtained from lattice imaging technique. We chose the Pd2Si because it has a hexogonal structure (2) and grows epitaxially on (111) Si with the orientation relationships:(001)Pd2Si // (111)Si and [100]Pd2Si // [110]Si. The epitaxially-grown film will provide a large area or the single crystal Pd2Si for lattice imaging.

The Si wafers used were n-type, 10 to 20 Ω-cm, (111) oriented, and HF etched before deposition. The deposition of Pd film of 100Å was carried out by e-beam evaporation at a rate of ∼5Å/sec. in a vacuum of 2x10-7 torr onto room temperature substrates.
Low resolution STEM imaging
Authors: Hutchings R. , Jones I.P. , Loretto M.H.
Published: June 2020

Introduction

In recent papers (Fraser and Jones 1975, Fraser, Jones and Loretto 1977) it has been shown that STEM does not offer an increase in penetration of metallurgical specimens over that available in CTEM. It was argued that two factors, lack of intensity and a top/bottom effect, limit penetration in both CTEM and STEM and the relative importance of these factors is expected to differ for different experimental requirements. The present paper examines an experiment with requirements such that the intensity limit in STEM may be overcome by using a large probe of about 40nm diameter.

Experimental

Specimens of a complex copper alloy (Long 1977) containing particles of Cr (∼10nm in diameter) and particles of SiO2 (∼0.5 μm in diameter) have been examined at 100kV in STEM and CTEM using a Philips EM40O fitted with a conventional tungsten hairpin filament. In addition micrographs have also been obtained at 1MV in an AEI EM7. The contrast mechanism was of structure factor type.
Bright field and weak-beam images of dislocations gliding on (001) planes in F.C.C. metals
Authors: Karnthaler H. P. , Korner A.
Published: June 2020

In f.c.c. metals slip is observed to occur generally on {111} planes. Glide dislocations on intersecting {111} planes can react with each other and form Lomer-Cottrell locks which lie along a <110> direction and are sessile since they are split on two {111} planes. Cottrell already pointed out that these dislocations could glide on {001} planes if they were not split. The first study of this phenomenon has been published recently. It is the purpose of this paper to report some interesting new details of the dislocations gliding on {001} planes in pure Ni, Cu, and Ag deformed at room temperature.

Single crystals are grown with standard orientation and strained into stage II. The crystals are sliced parallel to the (001) planes. The dislocation structure is studied by TEM and the Burgers vectors ḇ and glide planes of the dislocations are determined unambiguously.

In Fig.l primary P and secondary S dislocations react and form composite dislocations K.