bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sample preparation of sub-micron precipitates in rapidly solidified Mg-20Nd
Authors: Omlor Ralph E. , Robertson Lt Erica , Lloyd Pamela F. 
Published: June 2020

The Mg-20Nd melt spun ribbonsare being examined in depth because of their potentiodynamic polarization response as compared to that of 7075-T73 aluminum. The Mg-20Nd ribbon exhibited pseudopassivation behavior at a current density approximately one order of magnitude less than the aluminum alloy. In previous work, this was found to be due to the presence of a tessellatal precipitated network which formed in the ribbons during melt spinning. EDS results on TEM foils gave similar compositional values on both matrix and precipitates. These results were not trusted due to the small size and large volume fraction of the precipitates.The Mg-20Nd ribbon was swabbed with a dilute solution of sulfuric acid to loosen the particles in the matrix. A heavy oxide film was also formed on the surface at this time. Plastic replication solution was then applied to this surface and stripped away when dry. The particle side of the plastic film was then carbon coated. This film was placed on 3mm grids and the plastic dissolved away leaving the carbon film and the oxide precipitate mixture.
An integral field emission “microSEM” for UHV surface analysis
Authors: Veneklasen Lee H. , Todd George , Poppa Helmut 
Published: June 2020

It has been recognized for some time that the application of high sensitivity surface analytical techniques at high spacial resolution is highly desirable. For surface characterization, concentration distribution and topography are superior to average concentration, and sensitivity is increased by localizing the analysis to regions of higher concentration. In the field of Auger electron spectroscopy, this trend is reflected by the increasing popularity of scanning AES (SAM) instrumentation.Due to the low yield of characteristic secondary particles (e.g. Auger electrons or X-rays), the central technological challenge is the delivery of relatively large beam currents into sufficiently small probes (often <30nm). However, electron optical design must also provide for optimum detector collection efficiency, for in many cases beam induced alterations and specimen damage rather than electron optics may limit the useable beam current in small probes.Two basic instrumental configurations are in use; the off-axis approach that treats beam generation and signal detection systems as isolated entities, and the coaxial approach in which the electron gun is an integral part of the detector (e.g. cylindrical mirror analyzer).
Outline of an imaging magnetic energy filter free of second-order aberrations
Authors: Pejas W. , Rose H. 
Published: June 2020

An imaging magnetic energy filter free of second-order aberrations is proposed for a high-resolution fixed-beam transmission electron microscope. The filter consists of four homogeneous bending magnets symmetrically arranged about the central plane of the filter (see Fig. 1). A distorted stigmatic image of the object plane is located at the midplane (see Fig. 2). Due to the required midplane symmetry of the fields and the Gaussian rays, the dispersion of first degree, the second-order aperture aberration, and the second-order distortion vanish in the image plane. The remaining second-order aberrations in this plane, the inclination of image field, and the field astigmatism consist of three linearly independent components. These aberrations decisively limit the field of view.Energy selection is performed at the diffraction image D2 on the far side of the filter. The field aberrations cause the selected energy to depend on the off-axial position of the object points [1]. To guarantee a large field of view with equally well-resolved image points, all second-order aberrations must be cancelled or sufficiently reduced.
Theoretical investigations on rotationally symmetric guns with field-emission source
Authors: Kern D. 
Published: June 2020

The principal procedure in computing the properties of an electron-optical system consists of two steps, first the calculation of the electric or magnetic field, and then the calculation of trajectories, from which the properties may be obtained.In regions free from current and charge, the electric or magnetic field follows as the gradient of a solution of Laplace's equation for a scalar potential. Analytic solutions are known only for a few specific cases. They are essentially based upon the separation of Laplace's equation in curvilinear orthogonal coordinates; the difficulties arise from boundaries which cannot be represented as coordinate surfaces.With a numerical solution of this problem, using either the finite-element or the finite-difference-method, difficulties arise when dividing the region considered into triangles or meshes, since the dimensions of the electrodes and of the tip in a field emission gun differ by several orders of magnitude. Combining an analytical with a numerical solution, these difficulties can be avoided.
New type electron gun with electrostatic and electromagnetic lenses
Authors: Ichinokawa T. , Maeda H. 
Published: June 2020

I. IntroductionThermionic electron gun with the Wehnelt grid is popularly used in the electron microscopy and electron beam micro-fabrication. It is well known that this gun could get the ideal brightness caluculated from the Lengumier and Richardson equations under the optimum condition. However, the design and ajustment to the optimum condition is not so easy. The gun has following properties with respect to the Wehnelt bias; (1) The maximum brightness is got only in the optimum bias. (2) In the larger bias than the optimum, the brightness decreases with increasing the bias voltage on account of the space charge effect. (3) In the smaller bias than the optimum, the brightness decreases with bias voltage on account of spreading of the cross over spot due to the aberrations of the electrostatic immersion lens.In the present experiment, a new type electron gun with the electrostatic and electromagnetic lens is designed, and its properties are examined experimentally.
In-situ cleaning of crystal surfaces in electron microscope by means of ion sputtering
Authors: Yagi K. , Morita E. , Takayanagi K. , Kobayashi K. , Honjo G. 
Published: June 2020

In-situ observation of epitaxial thin film growth in an electron microscope requires a versatile UHV electron microscope (10-8-10-10Torr) [1] and clean surface preparation techniques for thin substrate crystals. Present authors have developed following clean substrate preparation methods. (a) Flash cleaning by heating an air cleaved layer structure thin crystal at 800°C at the UHV specimen position (MoS2, graphite)[2].(b) In-situ sublimation cleaning at specimen position (PbS) [3]. (c) In-situ vacuum cleavage at specimen position by means of electron beam flashing (MgO)[4]. (d) In-situ epitaxial deposition of substrate crystal on thin crystals prepared by the methods (a) and (c) (Ag, Au, Pd, Pb Se, SnTe,..)[5]. Thus the wide range of substrate-deposit combinations has been studied and various growth modes have been observed in detail.In the present paper, in-situ ion sputter cleaning technique and its applications to MgO, Au and Si are described. Since the technique can clean surfaces of thin crystals which are prepared by chemical or elect-rolitical etching of bulk crystals, it allows us wider selection of substrate crystals.
Electron microscopy on etched thin foils. A comparative SEM, STEM and TEM analysis
Authors: Österlund R. , Vingsbo O. 
Published: June 2020

During the last decade, much effort has been devoted to relations between structure and mechanical properties, particularly in metals. The need for sophisticated structure studies has increased accordingly. Combinations of different types of microscope methods have been tried, for example by performing optical and scanning electron microscopy (SEM) on etched metallographic sections.Particularly in the case of more intricate phase analyses, it is often necessary to add information about the internal structure by means of transmission electron microscopy (TEM). The scope of the present work has been to combine the advantages of the “classical” methods of studying etched surfaces with those of transmission studies of the same field of observation. For that purpose, the scanning transmission electron microscope (STEM) technique is ideal, and has been applied on thin foils, which, after ordinary electro-polishing, were etched (nital, 10 sec.) and thereby given a structure-related surface topography. The microscope used was a JEOL 200B TEM with scanning attachment, operated at 200 kV in emissive SEM, STEM and conventional TEM mode.
A non-cyanide method of electropolishing silver
Authors: Lyles R. L. , Rothman S. J. , Jäger W. 
Published: June 2020

Standard techniques of electropolishing silver and silver alloys for electron microscopy in most instances have relied on various CN recipes. These methods have been characteristically unsatisfactory due to difficulties in obtaining large electron transparent areas, reproducible results, adequate solution lifetimes, and contamination free sample surfaces. In addition, there are the inherent health hazards associated with the use of CN solutions. Various attempts to develop noncyanic methods of electropolishing specimens for electron microscopy have not been successful in that the specimen quality problems encountered with the CN solutions have also existed in the previously proposed non-cyanic methods.The technique we describe allows us to jet polish high quality silver and silver alloy microscope specimens with consistant reproducibility and without the use of CN salts.The solution is similar to that suggested by Myschoyaev et al. It consists, in order of mixing, 115ml glacial actic acid (CH3CO2H, specific wt 1.04 g/ml), 43ml sulphuric acid (H2SO4, specific wt. g/ml), 350 ml anhydrous methyl alcohol, and 77 g thiourea (NH2CSNH2).
Orientation control of vacuum deposited epitaxial metal films by applying external stress
Authors: Maruyama S. , Yamamoto K. 
Published: June 2020

The orientation of vacuum deposited, epitaxial metal films was controlled, by applying external stress, on copper gold ordered alloy, and on gold manganese ordered alloy.Ordered tetragonal or quasi-tetragonal epitaxial films such as CuAuI and gold manganese α″ have the mixed orientation of the shorter axis normal and parallel to the film plane,in the usual deposition in vacuum, i.e., (i)when the copper was deposited immediately after the gold was deposited, on cleaved surface of rock salt and homogenized, as is shown in Fig.la., or (ii)when it is formed by flash method (the two constituent atoms are deposited simultaneously), as shown in Fig.2a. This is very troublesome for the analysis or interpretation of the ordered structure of alloys. The author controlled the orientation so that the shorter axis is overall normal to the film plane in both CuAuI and gold manganese α″ by the following way. An epitaxial gold film held at room temperature for one night was rapidly heated to 350°C (at the rate of 15°C per minute), then copper or manganese was deposited onto it at that temperature, and homogenized
Growth and morphology of crystals in vacuum-deposited tellurium films
Authors: Shiojiri M. , Saito Y. , Sato M. 
Published: June 2020

Crystals of Te prepared by vacuum-deposition on cleaved NaCl surfaces at temperatures ranging from 20 to 140°C have been studied by SEM and TEM observations. The deposition was done at a deposition rate of 0.3 nm/s, monitored with quartz crystal oscillating microbalance. After the deposited films were backed by carbon films, they were wet-stripped from the substrates and mounted on standard electron microscope grids.Figure 1 shows electron micrographs of the films in different thicknesses which were prepared at different substrate temperatures. At the initial stage of deposition, spherical or polyhedral crystallites with the hexagonal structure grew with random orientations on the substrates. On the substrate at room temperature, the crystallites became large keeping the same shape and the number of the crystallites increased, as the film thickness increased. On the substrates above 80°C, they grew into slender crystals elongating along the c-axes, with increasing film thickness. The number of crystals did not increased so much.
Imaging of tilted, extended, thin phase-objects
Authors: Schiske P. 
Published: June 2020

In images of extended strongly tilted specimens, different parts of the object are subject to different defocus. This makes it possible to obtain, by a single exposure, an overall view of the transfer properties of the objective [1,2]; on the other hand, in reconstruction work it requires the use of correcting procedures [3]. The importance of both points seems to justify formal investigation--restricted here to thin phase objects. The geometrical data are shown in Fig. 1; the axis of tilt is normal to the plane of the drawing and is used as coordinate axis X2. Representing the scattered amplitude by u(k1,k2) where spatial frequencies k by δ = λk represent the inclination δ of the different components of the wave field a(x1,x2,z), one hasPutting z = x1 one finds for the amplitude immediately beyond the object(1)
Signal-to-noise enhancement in bright field images by incoherent superposition
Authors: Kunath W. 
Published: June 2020

Bright field imaging of heavy single atoms with hollow cone illumination results in images with only slightly reduced central contrast, compared to axial illumination, but strongly suppressed subsidiary maxima. This holds for certain values for the cone angle and defocus and is due to the triangle-shaped contrast transfer function. Computer-simulated micrographs of Hg atoms on a carbon support film show that the inherent structural noise is suppressed as well, resulting in twice as good a signal-to-noise ratio compared to axial illumination. The phase grating approximation is used.The computer-generated carbon film with an area of 48 Å by 48 Å is a random network of atoms, the sampling distance corresponding to 0.75 Å. It is fitted to give a noise-to-background ratio N = 5% in the Scherzer focus with the data λ = 3.7 • 10-2 A; Cs = 0.5 mm; Cc = 0.8 mm of our microscope.
Image contrast of cluster atoms taking account of inelastic scattering
Authors: Kanaya Koichi , Oikawa Tetsuo , Mizukoshi Nobuaki , Ikeguchi Kou , Shino Masayuki , Hojou Kiichi 
Published: June 2020

Based on the image formation theory, the image contrast of cluster atoms taking account of inelastic scattering are simulated with the experimental result for carbon film made by sputter deposition. The contrast g for the cluster atoms has been calculated by integrating the scattering wave for coherent waves, and for incoherent waves the amplitude scattered outside the limiting angle αset by the aperture respectively,in which the first term (real part of the wave function we (υj,γj))is the phase contrast due to the total phase which is combined by ηj(O) and γj. The second term and the third term show the amplitude contrast by the elastic and inelastic scattering absorption respectively. The wave function of inelastic scattering Wine(υj,γj) is given by
Structure and migration of planar defects in crystals observed in atomic scale
Authors: Hashimoto H. , Sugimoto Y. , Takai Y. , Endoh H. 
Published: June 2020

As was demonstrated by the present authors that atomic structure of simple crystal can be photographed by the conventional 100 kV electron microscope adjusted at “aberration free focus (AFF)” condition. In order to operate the microscope at AFF condition effectively, highly stabilized electron beams with small energy spread and small beam divergence are necessary. In the present observation, a 120 kV electron microscope with LaB6 electron gun was used. The most of the images were taken with the direct electron optical magnification of 1.3 million times and then magnified photographically.1. Twist boundary of ZnSFig. 1 is the image of wurtzite single crystal with twist boundary grown on the surface of zinc crystal by the reaction of sulphur vapour of 1540 Torr at 500°C. Crystal surface is parallel to (00.1) plane and electron beam is incident along the axis normal to the crystal surface. In the twist boundary there is a dislocation net work between two perfect crystals with a certain rotation angle.
Some aspects of the defect structure in an austenitic stainless steel
Authors: Gonzalez R. , Bru L. 
Published: June 2020

The analysis of stacking fault tetrahedra (SFT) in fatigued metals (1,2) is somewhat complicated, due partly to their relatively low density, but principally to the presence of a very high density of dislocations which hides them. In order to overcome this second difficulty, we have used in this work an austenitic stainless steel that deforms in a planar mode and, as expected, examination of the substructure revealed planar arrays of dislocation dipoles rather than the cellular structures which appear both in single and polycrystals of cyclically deformed copper and silver. This more uniform distribution of dislocations allows a better identification of the SFT.The samples were fatigue deformed at the constant total strain amplitude Δε = 0.025 for 5 cycles at three temperatures: 85, 293 and 773 K. One of the samples was tensile strained with a total deformation of 3.5%.
Interstitial defect clusters in non-stoichiometric NiAl
Authors: Mukerjee D. , Loretto M.H. , Smallman R.E. 
Published: June 2020

IntroductionAs part of an extensive study of the nature of defect structure in B2 alloys the nature of defects in NiAl is being studied in some detail. In earlier work Ball reported and interpreted observations of unusual lattice defects in Al-rich NiAl. He showed that these defects lay on {100} and considered several possible models to account for the intrinsic displacement contrast observed. The absence of such defects on the Ni-rich side of stoichiometry was taken as confirmation of his chosen model. In the present paper it is shown that similar defects do in fact occur in Ni-rich specimens and that the nature of the displacement fringe contrast is extrinsic on both sides of stoichiometry. Possible formation mechanisms and structures of these defects are discussed.ExperimentalSpecimens with compositions covering the whole composition range both sides of stoichiometry were prepared by argon arc melting appropriate weighed amounts of Ni and Al, and discs for examination by electron microscopy prepared from these as-cast specimens and from specimens homogenized at 1300°C for 72 hrs.
Progress in transmission electron microscopy of NaCl crystals
Authors: Strecker H. , Strunk H. 
Published: June 2020

ScopeUpon exposure to ionizing radiation, NaCl, like all other alkali halides, is damaged severely, mainly by formation of defects due to electronic excitations. Investigation by transmission electron microscopy is hence only possible, if special experimental measures are taken in order to reduce this type of damage effectively. This has been achieved by cooling the specimens to <20K in the microscope /1/ or by using a high accelerating voltage of ≥400kV /2/. The simultaneous application of both precautions /3/ provides observation times long enough to permit a detailed contrast analysis and has been demonstrated successfully in the investigation of pure NaCl crystals.It is the aim of the present paper to survey the recent progress of this experimental technique. Some details will be reported on the dislocation distribution observed in (001)-orientated NaCl crystals, which were deformed in compression at 220K and 78K. The preparation of the samples involved sectioning, subsequent pinning of the dislocations by X-irradiation, waterfreee thinning and transfer into the microscope /4/.
A standard for transmission electron spectroscopy
Authors: Maher Dennis , Joy David , Mochel Peggy 
Published: June 2020

A variety of standard specimens is needed in order to systematically investigate the instrumentation, specimen, data reduction and quantitation variables in electron energy-loss spectroscopy (EELS). Pure single element specimens (e.g. various forms of carbon) have received considerable attention to date but certain elements of interest cannot be prepared directly as thin films. Since studies of the first and second row elements in two- or multicomponent systems will be of considerable importance in microanalysis using EELS, there is a need for convenient standards containing these species. For many investigations a standard should contain the desired element, or elements, homogeneously dispersed through a suitable matrix and at an accurately known concentration. These conditions may be met by the technique of implantation.Silicon was chosen as the host lattice since its principal ionization energies, EL23 = 98 eV and Ek = 1843 eV, are well removed from the K-edges of most elements of major interest such as boron (Ek = 188 eV), carbon (Ek = 283 eV), nitrogen (Ek = 400 eV) and oxygen (Ek = 532 eV).
Electron back-scattering patterns in a field emission gun scanning electron microscope
Authors: Harland C.J. , Klein J.H. , Akhter P. , Venables J.A. 
Published: June 2020

INTRODUCTION.The electron back-scattering pattern (EBSP) is a simple means of obtaining the crystallographic orientation of samples in the SEM. Kikuchi bands are observed on a fluorescent screen ∼15mm in front of a (tilted) sample /l/ and shadows, for example of three spherical balls, can be used to obtain orientation determinations accurate to ± 0. 5° /2/. We have also shown that a fibre-optic detector of angular diameter <2θB can be used to form images of polycrystalline material with markedly increased grain contrast /3/.In the present paper we report that these techniques have been transferred onto an ultra-high vacuum SEM equipped with a field emission gun (FEG). The higher brightness of the FEG enables the spot size to be reduced markedly. The transition between the orientation of one grain and the next has been shown to be as sharp as 50nm. Shifts due to sub-grain boundaries down to ∼1° can be readily seen
Cell structure properties during in situ creep experiments in the H.V.E.M.
Authors: Caillard D. , Martin J.L. 
Published: June 2020

The behaviour of the dislocation substructure during the steady stage regime of creep, as well as its contribution to the creep rate, are poorly known. In particular, the stability of the subboundaries has been questioned recently, on the basis of experimental observations |1||2| and theoretical estimates |1||3|. In situ deformation experiments in the high voltage electron microscope are well adapted to the direct observation of this behaviour. We report here recent results on dislocation and subboundary properties during stationary creep of an aluminium polycristal at 200°C.During a macroscopic creep test at 200°C, a cell substructure is developed with an average cell size of a few microns. Microsamples are cut out of these specimens |4| with the same tensile axis, and then further deformed in the microscope at the same temperature and stain rate. At 1 MeV, one or a few cells can be observed in the foil thickness |5|. Low electron fluxes and an image intensifier were used to reduce radiation damage effects.