bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmission electron microscopy of 1/4-micron SOI structures
Authors: Conner J. R. , Theodore N. D. , Arney S. C. , Carter C. B. , MacDonald N. C.
Published: June 2020

As silicon devices are scaled into the submicron regime, parasitic circuit elements due to wiring and junction capacitance become increasingly significant. One way to reduce these parasitic elements is to fabricate circuits in thin silicon layers on an insulating substrate. Silicon-On-Insulator (SOI) structures can be fabricated by various techniques, including ion implantation of oxygen, recrystallization of amorphous or polycrystalline silicon films deposited on insulating thin films, and oxidation of porous silicon. A new SOI technique, in which islands of silicon become isolated from the silicon substrate during a thermal oxidation step, has been optimized for submicron-width silicon structures. The large stresses associated with the two-dimensional oxidation give rise to the generation and propagation of dislocations in the silicon island during the oxidation sequence. The characterization and removal of these dislocations is an important factor in optimizing these structures.

TEM samples have been prepared to evaluate the defect configurations present in these novel submicron SOI structures.
Investigation of CPE/PVC morphology via STEM
Authors: Rightor E. G. , Garcia-Meitin E. I. , Liou D. W.
Published: June 2020

Microscopic characterization of the phase morphology of poly(vinyl chloride) (PVC) modified with chlorinated polyethylene (CPE) is vital to understanding the blend physical properties. A 2-3 week CPE selective staining technique, developed by Fleischner et al., has been the mainstay for recent TEM investigations of CPE/PVC. Several researchers employing this method have reported a network structure of CPE surrounding primary PVC particles.

Rapid electron beam-induced dehydrochlorination of chlorinated polymers prohibits TEM examination of unstained sections. Chemical changes resulting from such dehydrochlorination of polymers was addressed recently by Vesely and Finch. In this study we investigated unstained thin sections, obtained at ambient temperature with a diamond knife, by scanning transmission electron microscopy (STEM) on a JEOL 2000 FX.

As the STEM micrographs show (Figs. 1-3), sufficient contrast was available to distinguish CPE (light phase) from the PVC matrix (dark). Differences in initial chlorine concentration and rates of beam-induced mass loss most likely account for the contrast between phases.
Thin film standardless analysis used in TEM asbestos EDS analysis
Authors: Li X. , Xingxing J. , Zi-qin W. , Lee R. J. , Dunmyre G. R. , Anderson K. L.
Published: June 2020

A thin film standardless analysis method, based on the Cliff-Loriner factor k, has been used to do quantitative x-ray analysis of asbestos fibers in the TEM. The results of the analysis of four minerals at 120 keV were close to the theoretical value. The ionization cross section Q has been revised experimentally to improve the analysis of asbestos.

The Cliff-Lorimer factor has been used in TEM thin film analysis since 1975. The factor kAB is used in the following equation:

CA/CB= kABIA/IB

where CA and CB is the weight percent of the elements A and B. The IA and IB are x-ray intensities corresponding to elements A and B. In this paper the calculated k values2 will be used for standardless quantitative analysis.

In the thin film, when the effects of the backscattering electron, x-ray absorption, and secondary fluorescence are not considered, the x-ray intensity is

where pt is the mass depth AA is the atomic weight of element A, W is the fluorescence yield, L is the ratio of the x-ray lines and T is the detector efficiency.
Monte-Carlo simulation of intensity ratio Is/Ic from substrate and film to determine the film thickness
Authors: Guangxiang Jin , Jianlin Li , Li Xu , Ziqin Wu
Published: June 2020

The methods of thickness of film on substrate by electron probe have been published in literatures. It may be carried out simply by constructing a calibration curve from x-ray intensity measurments made on a series of films with known thickness on substrate.

Sweeney et al. obtained a calibration curve based on a calcula- tied x-ray Ø(p z). As the calculation of Ø(p z) is difficult, Cockett and Davis, proposed using the experimental Ø(p z) of Castaing and Descamps. Bishop and Poole utilised Ø(p z) established by Monte-Carlo calculation for calibration curve.

Huchings' method took into account the different electron scattering and absorption in the film on substrate and the bulk standard.

Reuter et al., constructing a curve of Ic/Ib (Ic, intensity of the film on substrate; Ib, intensity of bulk standard) versus electron accelerating voltage E, exterpolate the curve so that Ic/Ib equals to 1, the excited x-ray depth obtained is just equal to the thickness of the film. The thickness of the film can be obtained by the use of an appropiate equation of excited x-ray depth.
Pre-commercial days in SEM
Authors: Boyde A.
Published: June 2020

These are personal reminiscences of my earliest experiences with SEM, not a history of the evolution of the practical instruments. However, to cover that ground in short, although demonstrated as a principle in Germany before war, the really practical development of SEMs began in Cambridge in under the direction of Charles Oatley. Beginning with MacMullan, continuing with a series of PhD students whose names today are literally hall of fame of the field, his team had really proved the potential of method by the mid-1950s. As this development happened in a university engineering laboratory, there was only one working instrument at a time, and that was when it worked. The principles were far more important than actually having an instrument which people could come and use! (My friends in similar laboratories today are still touched with the same problem). The pulp and paper people in Canada were the first to see the practical importance of SEM for their own research and had KCA Smith at the Cambridge University Engineering Labs build one to be used as a microscope.
Results on obtaining structural and analytical information with high lateral resolution in a STEM
Authors: Hubert G. , Krisch B. , Willasch D.
Published: June 2020

A unique feature of high-performance STEMs is their ability to combine high-resolution imaging with the possibility to perform structural and chemical analysis in areas considerably smaller than 10 nm. The STEM ELMISKOP® ST 100 F has been used to demonstrate some of the potential applications in various modes of operation.

Lattice imaging and defect analysis: It is well known that the unit cell charge distribution of certain crystals can be imaged in phase contrast TEM for structure determination and the investigation of lattice defects on an atomic level. In STEM one can obtain similar lattice images in phase contrast using a small-angle detector which samples the interference pattern in the detection plane between the undiffracted and at least one Bragg-diffracted wave (indicated in Fig.la by their wave vectors). Two ways of arranging the detector are possible: For axial (Fig.1a) or symmetrical imaging conditions (Fig.lb). Axial imaging includes instrument-induced chromatic aberration and yields an isotropic transfer function, symmetrical imaging excludes chromatic aberration but leads to an anisotropic transfer function not suitable for most applications.
Reduction of aberrations by new optimization techniques
Authors: Szilágyi M.
Published: June 2020

A novel method has been proposed by the author for minimizing the aberrations of electron optical systems [1ś. The method involves restricting the possible electrostatic or magnetic field distributions to those connecting the intersection points of a rectangular computational grid by straight lines and gives a recursive algorithm for choosing distributions that minimize a given combination of aberration coefficients.

The application of this method to the minimization of the spherical aberration of round magnetic lenses leads to interesting results [2ś. A graph of optimized h(z) distributions of the reduced flux density along the optical axis is shown in Fig. 1 for the case of δ = Δh Δz = 0.005 where Δh andΔz are the linear dimensions of a unit cell of the computational grid. In this case the object is immersed into the field at z = 0. A rich variety of different field distributions has been obtained.
Compensation of aberrations of deflected electron probe by means of dynamical focusing with stigmator
Authors: Baba Norio , Ito Yasuhiro , Kanaya Koichi
Published: June 2020

An electron beam passing through a deflecting field is, in general, subject to aberrations such as distortion, astigmatism and coma in accordance with the deflecting angle. Accordingly, aberration defects of deflected beam are most serious limiting factor in performance of high resolution scanning electron microscopes.

Based on the aberration formula(Wendt 1942, 1947 and Glaser 1956a), the distorted spot patterns of an electron probe deflected at two dimensional directions are calculated by using the conventional form of deflector field f (z) = [1+(z/a)2]-m. The important compensation conditions are induced by means of dynamical focusing with the stigmator.

1] Field distribution and magnitude of deflection

The magnitude of deflection by the electro-static field is given by,

where E(z) is the axial field strength, Φ the accelerating potential, and za and zb are the co-ordinates of the entrance and specimen position, respectively. Now, assuming the function E(z)/Eo=[1+(z/a)2]-m (1) which corresponds to the axial field strength distributions of semi-infinite co-planar sheets(m=l/2), parallel cylinders or wires(m=l) and parallel plates with fringing effects(m=l∼5), deflection distances e and angles |e'|=α for various deflection geometry can be expressed analytically.
Advantages and limitations of a condenser objective for minimum exposure
Authors: Herrmann K.-H. , Kowalsky U. , Kunath W. , Weiss K. , Zemlin F.
Published: June 2020

A single field condenser objective permits the imaging of a diaphragm onto the specimen such that areas with diameters smaller than 1000 Å can be illuminated. Combined with an electronic deflection system, this feature is particularly advantageous for radiation-sensitive specimens which should be exposed for the minimum dose required by the recorder.This method is preferable to others which, for example, require mechanical movement of the stage. In addition it can be directly combined with electronic image recording systems [1].

A two-stage deflection system fabricated by printed circuit techniques [2] can be readily fitted into the upper part of the objective. The printed pattern is such that the current produces an almost homogeneous deflecting field. A second one-stage deflecting system in the intermediate lens system provides automatic retracking of the image such that by suitable control only the image with respect to the detector is moved, and not the illuminated region
Proposal for an electrostatic energy filter and a monochromator
Authors: Plies Erich
Published: June 2020

Both instruments suggested here are composed of several cylindrical mirror analyzers (CMA) with the centres of object and image on the cylinder axis, see fig. 1. Usually the whole 360° ring zone of the CMA is used but in our case the electrons fly only within a segment of the ring zone. In the curvilinear xyz coordinate system of this bundle, there exist five fundamental rays xα, yβ,xγ,yδ and xϰ (fig. 1). As is well-known from [1], 2nd-order focusing occurs in the first principal section if ⊝=42.31° and R2/R1 = 3.705 (relativistic effects and fringing fields neglected). 50kV electrons need ⊝=43.07° and R2/R13.660. Due to the axial symmetry, the beam is also focused in 2nd order in the 2nd principal section. If one shifts the curved optic axis in the Z-direction, one obtains the ray γxγ.The trajectory is found using Helmholtz's theorem and the conservation of the Z-component of the angular momentum.
Electrostatic energy analyzers for electron microscopes
Authors: Ovsyannikova L.P , Yavor S.YA. , Ioffe A.F.
Published: June 2020

The application of energy analyzers in electron microscopy, the raster one in particular, is an interesting and comparatively new trendI-3. The analyzers can be used, for instance, for separating the elastically and inelastically scattered electrons, which leads to substantial improvement of the image contrast, and, accordingly, the space resolution. Monoenergetic images of a specimen obtained with energy analyzers permit of judging the topography of the specimen surface in connection with various physical properties of the specimen.

At present, cylindrical mirrors are usually used as the analyzers for the above purpose. They are applicable, however, only for wide angle beams (the optimal angles lie within the range of 40°-50°).

We propose an energy analyzer designed to operate both at narrow and wide angles of beam.

The analyzer consists of two coaxial electrodes in the shape of surfaces of revolution, i.e. hyperboloids, paraboloids, cones (Fig.). Ringed windows (I,2) are cut in the electrodes for passage of a beam which has the form of a hollow cone.
The ANL HVEM-tandem accelerator facilities
Authors: Lyles R. , Taylor A. , Merkle K. , Okamoto P. , Pronko P.
Published: June 2020

The ANL HVEM-TANDEM accelerator facilities are being developed to provide a unique combination of techniques for basic studies in the field of materials science. In addition to the methods of high voltage electron microscopy, the ion accelerator system will provide ion beam analysis and ion bombardment - implantation capability either in the HVEM or in an adjacent target area. The installation of the HVEM is completed and constitutes the first step in the development of a materials research laboratory, which will include a HVEM/ion beam interface with a 300 kV ion accelerator and a 2-MV tandem accelerator. The plan layout of these facilities is shown schematically in Figure 1.

ANL's 1.2 MeV HVEM is an improved version of the AEI EM-7 and has a guaranteed resolution of 5 Å point-to-point. The design of the microscope contains a number of unique features. These include a specially designed ion beam access flight tube, instrumentation for two independently adjustable dark field conditions, 100 - 1200 kV continuous-mode accelerating voltage selection, a negative ion trap, and an ion- pumped specimen chamber.
The use of scintillation detectors in the STEM
Authors: Wiggins J.W.
Published: June 2020

There are several characteristics desired of an electron detector that is to be used in a STEM. Depending on the particular instrument, one would like to have some or all of the following characteristics. It should have an output fast enough to keep up with the fastest scan rate of the microscope and should not introduce any noise into the signal. It should allow fabrication into sophisticated geometries required by some contrast mechanisms; for example, as an annulus for dark field contrast or as a sharp, straight edge for use as a spectrometer slit. Finally, it should have a high resistance to radiation damage by the electron beam.

Single crystals of europium-activated calcium fluoride [CaF2(Eu)] have been used as scintillation detectors because they satisfy all of the characteristics proposed above and are not even very expensive.

The complete electron detector consists of an appropriately shaped scintillator, a light-collection device, and a photomultiplier to convert light to an electrical signal.
Multi-purpose backscattered electron detector
Authors: Kikuchi M. , Takashima S.
Published: June 2020

Backscattered electrons (BSE) permit a variety of information regarding the specimen, e.g., composition, topography, magnetic domain structure, crystalline states, etc., to be obtained. However, since conventional BSE detectors are all single-purpose designed, several different detectors are required to obtain the required variety of information.

In order to circumvent this inconvenience, we have developed a multi-purpose BSE detector system. As shown in Fig. 1, the detector can be freely rotated around the specimen surface. In addition to which, the distance between the detector and the specimen can be varied. The newly developed solid state detector used in this system possesses high sensitivity and high response characteristics. Some advantages and applications of the system are given below.

1. By setting the detector at the low and high takeoff angle positions, topographic contrast and composite contrast (Z-contrast) can be respectively enhanced.

2. By using the rotation and distance varing mechanisms in combination, the optimum detecting condition for ensuring a good magnetic domain image can be selected.
Image registration with a computer driven S.T.E.M.
Authors: Schepman A.M.H. , van der Voort J.A.P. , Mellema J.E.
Published: June 2020

A Scanning Transmission Electron Microscope (STEM) was coupled to a small computer. The system (see Fig. 1) has been built using a Philips EM400, equipped with a scanning attachment and a DEC PDP11/34 computer with 34K memory. The gun (Fig. 2) consists of a continuously renewed tip of radius 0.2 to 0.4 μm of a tungsten wire heated just below its melting point by a focussed laser beam (1). On-line operation procedures were developped aiming at the reduction of the amount of radiation of the specimen area of interest, while selecting the various imaging parameters and upon registration of the information content. Whereas the theoretical limiting spot size is 0.75 nm (2), routine resolution checks showed minimum distances in the order 1.2 to 1.5 nm between corresponding intensity maxima in successive scans. This value is sufficient for structural studies of regular biological material to test the performance of STEM over high resolution CTEM.
X-ray micro tomography in the scanning electron microscope
Authors: Brünger W.
Published: June 2020

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.

Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.

During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.
Reduction of contamination in analytical electron microscopy by using specially designed cold traps
Authors: Tomita T. , Harada Y. , Watanabe H. , Etoh T.
Published: June 2020

For conventional transmission electron microscopy, specimen contamination is not so important as to take it into account, because recent electron microscopes are designed so as to provide the specimen chamber with a vacuum of the order of 10-7Torr. However, in analytical electron microscopy, contamination still presents serious problems requiring solution, because a very fine electron probe (less than 200Å) remains stationary on the specimen for a few minutes. In this case, a contamination spot is formed by the reaction of the electron probe with hydrocarbon molecules adsorbed on the specimen surface. The present paper describes detailed observations of contamination spots caused by very fine electron probe and the reduction of contamination spots by means of a specially designed liquid nitrogen cold trap assembly.

This cold trap assembly shown in Fig. 1 consists of two traps; an inner trap and outer trap. The inner trap, which is a conventional type, is designed to enclose the specimen.
Stereo imaging in the shadow electron microscope
Authors: Dowell W. C. T.
Published: June 2020

Stereo imaging is not new to electron microscopy. Von Ardenne, who first published transmission pairs nearly forty hears ago, himself refers to a patent application by Ruska in 1934. In the early days of the electron microscope von Ardenne employed a pair of magnetic lenses to view untilted specimens but soon opted for the now standard technique of tilting the specimen with respect to the beam.

In the shadow electron microscope stereo images can, of course, be obtained by tilting the specimen between micrographs. This obvious method suffers from the disadvantage that the magnification is very sensitive to small changes in specimen height which accompany tilting in the less sophisticated stages and it is also time consuming. A more convenient method is provided by horizontally displacing the specimen between micrographs. The specimen is not tilted and the technique is both simple and rapid, stereo pairs being obtained in less than thirty seconds.
Epitaxial growth of very thin films of germanium
Authors: Hoeike C.W.
Published: June 2020

The preparation of germanium electron microscopy specimens by chemically polishing slices cut from a single crystal is a standard technique (1). Also, epitaxial growth of germanium on crystalline substrates has been achieved by vapour deposition (2,3). However, the selfsupporting very thin films required for high resolution, crystal lattice imaging experiments cannot be easily prepared by either method.

A uniform amorphous film of germanium of any desired thickness can be prepared, however, by vacuum evaporation of germanium from a tungsten basket onto a suitable substrate at any temperature below 500 K. This amorphous film will crystallize when heated to 675 K or more (2). By controlling the heating of the substrate during evaporation and subsequent crystallization, it is possible to induce epitaxial film growth on single crystal substrates.

The work described here has established the conditions necessary for the growth of germanium single crystal films 140Å thick, with [111] and [100] surface orientations.
A sputter source for electron microscopic preparation
Authors: Jakopić E. , Brunegger A. , Essl R. , Windisch G.
Published: June 2020

Coating electron microscopic specimens by sputtering yields particulary fine grained coatings of strong adherence. Two methods have been applied up to now. Their difference lies in the arrangement of target and specimen. If, in one case both, target and specimen are arranged inside the discharge chamber,damage by the discharge of sensitive specimens is possible (Fig.la). If, in the other case both, target and specimen are arranged outside the discharge chamber, focussing of the ions is necessary, above all for shadowing (Fig.lb).Simple ion guns of low energy (some keV) however, yield a relatively low ion current, so that coatings with materials which are difficult to sputter, such as tungsten, can hardly be produced. With ions of higher energy the gain of sputtering particles would certainly increase. However, the danger arises that ions scattered at the target and neutral particles of high energy could damage the specimen.

The basic idea of the new sputter source consists of arranging the target inside the discharge chamber but the specimen outside of it (Fig.2).
Beam shaping techniques in scanning electron lithography systems
Authors: Pfeiffer H. C.
Published: June 2020

A variety of beam shaping techniques are described which we have developed to overcome writing speed limitations inherent to the serial exposure of scanning electron beam lithography systems. We will present experimental results demonstrating the technical feasibility of the various shaping techniques. Figure 1 illustrates E-beam pattern generation by a Gaussian round beam and various shaped beam configurations. The SEM-type, Gaussian round beam exposes one image point at a time. The size of the beam spot is identical with the spatial resolution of the system and is typically 4 to 5 times smaller than the minimum pattern features. For shaped-beam systems, the spatial resolution given by the edge slope of the beam profile is decoupled from the size and shape of the beam spot. Consequently, a plurality of image points can be projected in parallel without loss of resolution. This combination of scanning and projection techniques provides a fast exposure rate without sacrificing the flexibility of computer-controlled pattern generation.
Fourier spectrum analysis of phase contrast of support film
Authors: Oikawa Tetsuo , Ishigaki Fumiko , Hojou Kiichi , Kanaya Koichi
Published: June 2020

In high resolution electron microscopy, it is most important to determine the defocus of electron micrographs of amorphous support films. The variation of spatial frequencies of phase contrast of support films was obtained from the phase shift of the electron waves caused by defocus and spherical aberration as well as the atomic phase, which are demonstrated by use of optical Fourier transforms. The spatial frequencies of phase contrast of films of tungsten, prepared by ion bombardment, which are useful as support films for high resolution electron microscopy, has been discussed analytically.

Taking account of atomic phase shift, the transfer function, which was originally presented by Thon (1966), was modified. Optical Fourier transforms are in similar to the calculated Fourier transforms of corre- sponding computed images. Accordingly, it turned out that the atomic phase shift should not be neglected. The thickness of tungsten film, in case of less than 2 nm thickness, can be determined by comparing the optical Fourier transforms with the calculated ones.
Bright-field image contrast and resolution in STEM and CTEM
Authors: Cowley J. M. , Au Andrew Y.
Published: June 2020

For the high resolution imaging of thin specimens, it has been shown by Cowley and Au that the bright-field image intensity may be written as

Here s(r) and c(r) are the two-dimensional Fourier transforms of the imaginary and real parts of the transfer function, A(u)sinx(u) and A(u)COSX(u), where A(u) is the aperture function, x(u) is the phase factor usually written

and u = (2sinθ)/λ is the magnitude of the two dimensional reciprocal space vector u;

Δf and Cs are the defocus and spherical aberration constants of the objective lens and the * symbol indicates a convolution integral. In deriving equation (1) we have assumed the validity of the phase object approximation but not the usual weak phase object approximation (WPOA) which applies only for the weak-scattering case that σφ(r)<<l, where σ is the interaction constant (=п/λE) and ϕ(xy) is the projected potential of the object. The WPOA is known to have severely restricted validity for crystalline specimens or for specimens containing heavy atoms such as negatively stained or positively stained biological material.
Dark-field STEM imaging and diffraction calculations of heavy atoms on amorphous support films
Authors: Krakow William
Published: June 2020

It has been noted by several investigators that the observation of single heavy atoms and small molecules in a high resolution electron microscope depends upon the discrimination between the image of the specimen and the support film used. Neglecting statistical noise due to the number of electrons the possibility of contaminant heavy atoms or structural noise caused by local arrangements of support film atoms remains.

To evaluate the effect of the interference of scattered wavelets from a few atoms in a support film a model of a 10Å thick amorphous film was obtained using random number generators. The atoms were then packed in a 100 x 100 x 10Å volume until the density of amorphous carbon was attained (2400 atoms) with the constraint that the atoms could not be closer together than the nearest neighbor distance in carbon (1.5Å). A system of computer programs was then employed to simulate microdiffraction patterns and dark-field scanning transmission electron microscope (STEM) images.
High resolution electron microscopy and atomic positions in gadolinium silicate
Authors: Nissen H.-U. , Wessicken R.
Published: June 2020

We have investigated the possibilities of imaging atomic positions having distances below 2Å in the example of a silicate, the monoclinic Gd2SiO5 which has a high degree of stability in the electron beam, intermediate cell parameters (a = 9.12, b = 7.06, c = 6.73 Å, β = 107°35', space group P21/c) and two species of atoms (Gd,Si) as main contributors to the contrast. The atomic parameters of the structure used for contrast calculations were given by Smolin and Tkachev (1969).

Through-focus series for the projections along [100] and [001] were made for several specimens using a JEM 100 C electron microscope equipped with a high resolution objective pole piece (Yanaka et al., 1974). Powder flakes with platy surfaces show cleavage steps (terraces) along margins, each of which has a rather constant thickness. The contrast pattern varies within a single terrace, most likely as a result of minute differences in orientation due to bending of the crystal flake.
A walking platinum complex
Authors: Hainfeld J. F. , Wall J. S.
Published: June 2020

After Albert Crewe et al. first detected single heavy atoms using a high resolution STEM in 1970, several enterprising microscopists atempted to use single heavy atoms as biological markers. The results were somewhat disappointing. Langmore found that specifically stained DNA rapidly lost its mercurial label, making sequencing this way impossible. Cole, Wiggins and Beer found that polynucleotides stained with osmium exhibited too much heavy atom motion to localize bases, but found that the osmium stayed with 5-10Å of the strands. Further work by Isaacson et al. quantified uranium atom motion at room temperature. It may be possible to reduce this atom motion by: 1) reducing the temperature, 2) reducing the beam dose, 3)better controlling the surface chemistry of the specimen or 4) using markers that do not move as much. The Brookhaven National Laboratory STEM was previously used to investigate possibility 1 and it was found that uranium atom motion was reduced by a factor of 2.2 in going from -40°C to -100°C.
Characteristics of phase contrast in STEM
Authors: Isakozawa S. , Todokoro H. , Nomura S. , Tonomura A. , Komoda T.
Published: June 2020

Observation of atoms and elemental analysis of micro-area by energy analyzer have been made with our field emission scanning transmission electron microscope(FESTE M), whose point resolution is around o.3nm, and the phase contrast resolution is better than 0.2nm(Fig. 1). With this instrument, the fundamental characteristics of phase contrast images were studied. Especially it is interesting to know if illuminating electron beam can get information of lattice spacing when the spacing is fairly larger than the spot diameter, and the behavior of lattice image by STEM is the same as that obtained by CTEM.

In the present experiment, phase contrast, bright field and dark field images are observed under the detecting angles of β1≤ 10-3 rad., β2≤ 10-2 rad. andrad, respectively (Fig. 2).

Th-phthalocyanine is selected as a specimen whose lattice spacing (d=1.34nm) is quite larger than the point resolution of the STEM (Fig. 3). The bright and dark field images are found to be almost the same at any defocus, except the reversed contrast
HRTEM observation of stacking and ordered interstratification in rectorite
Authors: Mckee Thomas R. , Buseck Peter R.
Published: June 2020

Rectorite (=allevardite) is a perfectly ordered mixed layer clay mineral consisting of double layer units of alternating 2:1 (or T-O-T) nonexpandable mica-like and expandable smectite-like 10Å component layers (1,2). Complete dispersion of Na-saturated rectorite results in flakes equal in thickness to the basic unexpanded (20Å) double layer unit. Mixed layered (or interstratified) clay minerals are ubiquitous in both sediments and epithermal deposits; however their routine identification is difficult and is based upon various assumptions concerning their X-ray powder diffraction characteristics. Therefore, rectorite was studied by high resolution transmission electron microscopy (HRTEM) to test existing mixed layering models.

Oriented specimens of air-dried rectorite (Fort Sandeman district, Baluchistan, Pakistan) were prepared by three methods: (a) ultrasonic dispersion in acetone, (b) diamond knife ultrathin-sectioning of epoxy embedded dispersions and (c) ion thinning of epoxy embedded aggregates. Dispersed mounts were also prepared after treatment with n-dodecylammonium ions to expand the smectite-like interlayers, producing a double layer repeat of 28Å (3).
High resolution electron microscopy of lanthanum phosphate crystals
Authors: Wheatley J. C. , Cowley J. M.
Published: June 2020

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.

Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.

The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).
Structure images of Si, Ge and Mos2 crystals and some application to radiation damage studies
Authors: Izui K. , Nishida T. , Furuno S. , Otsu H. , Kuwabara S.
Published: June 2020

Recently we have observed the structure images of silicon in the (110), (111) and (100) projection respectively, and then examined the optimum defocus and thickness ranges for the formation of such images on the basis of calculations of image contrasts using the n-slice theory. The present paper reports the effects of a chromatic aberration and a slight misorientation on the images, and also presents some applications of structure images of Si, Ge and MoS2 to the radiation damage studies.

(1) Effect of a chromatic aberration and slight misorientation: There is an inevitable fluctuation in the amount of defocus due to a chromatic aberration originating from the fluctuations both in the energies of electrons and in the magnetic lens current. The actual image is a results of superposition of those fluctuated images during the exposure time. Assuming the Gaussian distribution for defocus, Δf around the optimum defocus value Δf0, the intensity distribution, I(x,y) in the image formed by this fluctuation is given by
1 MV super-high-resolution electron microscopy of Nb2O5-WO3complex compounds with TTB type subcells
Authors: Horiuchi Shigeo
Published: June 2020

It is known that, over a composition range in a Nb2-O5-WO3 system, the crystal structure
of compounds is composed of subcells with tetragonal tungsten bronze ( TIB ) type.) Different models have however been reported for some of them. The crystals are usually prepared in sealed tubes and sometimes show different colours due to a reduction in spite of a definite starting composition. Moreover, they frequently include small domains, which make the structure analysis by x-ray diffraction very difficult. In the present study we examine a series of these compounds, prepared under various conditions, by a super-high-resolution, high-voltage electron microscope ( Hitachi 1250 ),in which the lattice fringes of 2.0 Å in width can be resolved at an accelerating voltage of 1 MV under an axial illumination with equipping a specimen goniometer.2)

Fig.l is a crystal structure image of 4Nb2O5.9WO3. According to electron diffractions the lattice parameters are a=12.3, b=36.6 and c=3.94 Å (orthorhombic).
High resolution lattice images of aluminum-copper alloy containing Guinier-Preston zones
Authors: yoshida H. , Hashimoto H. , Yokota Y.
Published: June 2020

Imaging of atomic structure of sinple crystals such as A1 and Au by the conventional high resolution electron microscope operated at 100 kV is still not very easy, because the lattice spacing of the crystals are smaller than about 2. 3 A, which equivalent to the resolving power of the microscopes. However, if the crystal lattice image is taken at the “Aberration Free Focus” condition(l), the fine structure of the crystal lattice can be photographed. Using this technique, atomic structure arround G.P. zone is studied in the present paper. Since local orientation in the specimen film disturbes the Bragg condition, we did not succeed to observe the atomic structure but could see the lattice fringes, which are formed by the systematic reflection from the crystal position. The fringe position obtained such condition corresponds to the position of atomic rows.

Disc specimens were spark-cut from the sheet of an Al-3.97%Cu alloy.
On alloy lattice images
Authors: Boyes E.D. , Gai P.L. , Skarnulis A.J.
Published: June 2020

The models that are suggested to describe precipitation reactions and phase transformations are almost always on the atomic scale, but the experimental techniques that can be used to examine the phenomena often either integrate the information from many events or operate at somewhat lower resolution. However, phase-contrast lattice imaging and possibly weak beam (Yoshida et al. 1976) techniques of transmission electron microscopy and field-ion microscopy (FIM) (e.g. Boyes et al. 1975 and 1977) can be useful. In principle the images can be interpreted to yield microanalytical data about individual planes or layers of atoms.

Images of (200) lattice planes, or more correctly fringes, have been produced from a rolled high purity Aluminium 4.3% Copper alloy containing GP2 or θ" zones. The polycrystalline material is used since the composition is more representative of the applications of this alloy. It was more difficult to produce images of this material than, for example of the visual gold test specimens: it is suggested that this may be due to the increased inelastic cross-sections.
Pipe diffusion along the segment of faulted dislocation loops in aluminum
Authors: Yamaguchi H. , Kawamoto H. , Yoshida S.
Published: June 2020

The motion of a perfect dislocation loop during annealing was examined by several workers. They proposed a mechanism of pipe diffusion and analyzed this motion. However, these studies on pipe diffusion may have some errors caused by the prismatic glide. In this paper we studied on the motion of faulted dislocation loops under the mutual interaction and estimated the activation energy for pipe diffusion along the dislocation segment of faulted loops.

Figure 1 shows schematically a pair of regular hexagonal faulted dislocation loops lying on the (111) plane in quenched aluminum as well as their images observed with an electron microscope, where (a) is the one taken from [001] direction before annealing, (b) and (c) are those taken from [001] and [011] directions after annealing at 95°C for 2 hours, respectively. In order to determine the vector S which connects the center of loop 1 and that of loop 2 in Fig. 1, three different coordinate systems (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3) are set up on a specimen, an electron microscope and a micrograph, respectively,(Fig. 2).
Electron microscope studies of climb of dissociated dislocations
Authors: Carter C.B. , Cherns D. , Hirsch P.B. , Saka H.
Published: June 2020

The mechanism of climb of dissociated dislocations in f.c.c. metals and alloys is not well understood. Climb of dislocations by absorption or emission of vacancies at existing jogs in dissociated dislocations has been observed using the “weak-beam” technique of electron microscopy, but the mechanism of nucleation of jogs is not clear. In this paper we report some results of experiments designed to study the nucleation problem, and more generally the mechanism of absorption of point defects under conditions of high supersaturation.

Thin (111) sections of deformed single crystals of Cu-Al alloys, of various compositions, have been electron irradiated in an AEI EM7 HVEM up to 1 MeV, either at room temperature, or elevated temperatures up to 200°C, using a goniometer heating stage. Observations under weak beam conditions have been made a) in situ in the HVEM b) at 100kV in an JEM100B, following irradiation in the HVEM. Interstitials produced by the irradiation are expected to be preferentially attracted to the dislocations because of the strong dislocation-interstitial interaction.
Observations of multipoles in creep deformed 20 Cr 30 Ni steel
Authors: Nilsson J.-O. , Dunlop G. L.
Published: June 2020

Introduction: Previously, reports have been made on the existence of multipoles in f.c.c. single crystals deformed in easy glide at room temperatures and theories have been developed for their effect on work hardening. It has been suggested that multipoles consist of a series of dipoles held closely together hy interaction of their strain fields (Fig.1) so that often individual dislocations cannot he resolved hy conventional techniques. The present investigation has analysed multipoles which have heen observed in a 20 Cr 30 Ni austenitic stainless steel deformed in creep at 800°C and a tensile stress of 30 MPa.

Results and Discussion: An example of multipoles seen in crept material is shown in Fig. 2. Adjacent dislocations in multipoles were identified as having burgers vectors of opposite sign by observing the change in dislocation image spacing obtained with equal and opposite diffracting vectors (+g and -g). An example of this is shown in Fig. 3.
The influence of the vacuum environment on the growth of electron irradiation induced voids
Authors: Buswell J.T. , Baker C. , Rickards G.K.
Published: June 2020

The variability of the void swelling in nimonic alloy P.E.16 produced by electron irradiation in the high voltage electron microscope has indicated some influence of the vacuum environment on the nucleation and growth of voids.

Specimens of double vacuum remelted nimonic alloy P.E.16 prepared under controlled conditions were preheated at 550°C for 1 hour in the microscope and then irradiated at temperature with 1 Mev electrons at a displacement rate of 2 x 10-3 per sec to a total dose of 10 - 20 displacements per atom.

Measurement of the vacuum environment around the specimen was made with a Vacuum Generators Micromass 2A mass spectrometer fitted with a long sampling tube extending to within 10cm of the specimen position. Control of the specimen environment was achieved by bleeding in a chosen gas by way of a Leybold leak valve fixed into the side of the specimen chamber so as to introduce the gas to a point within 5cm of the specimen position and on the same plane.
Bending of zirconium thin foils by in-situ ion irradiation
Authors: Parsons J.R. , Gilbert R.W.
Published: June 2020

In the present experiment the effects of neutron irradiation on zirconium were simulated by an in-microscope ion irradiation of prethinned foils on both sides of which were 60 to 80 Å of room-temperature oxide. Electron microscope observations were made of suitable thin areas prior to irradiation, during irradiation and after each incremental ion dose.

Ion Irradiation:- Specimens were irradiated in a Phillips 300 electron microscope with 100 keV oxygen ions emanating from oxide-coated emission filaments. The details involved in the preparation and activation of these filaments have been described elsewhere. Once activated the beam from the filaments consisted of oxygen ions and electrons thus permitting the simultaneous irradiation and observation of the specimen. Both ions and electrons had the same energy as determined by the microscope high voltage selector position. For all irradiations to be described, ions with an energy of 100 keV were used. Determination of the ion flux of approximately 1010to l012 ions cm-2sec-1, depending on the coated filament used, was made with a Faraday cage located just above the microscope final fluorescent screen
Electron microscopy investigation of clusters created in nickel by “in situ” rare gas ion irradiation
Authors: Lerme M. , Ruault M.O.
Published: June 2020

Irradiations by rare gas ions of 10 to 50 keV have been performed in nickel [10 ppm impurity) at temperatures between 100 and 500 K. The clusters have been observed “in situ” in a conventional electron microscope during irradiation(1).

1)Dose effect - Problems of cascade efficiency - For Argon ions of 25 and 50 keV and at irradiation temperatures between 100 and 500 K, the variation of the cluster density as a function of the dose is the same [see fig. 1). Two points are of interest :-the existence of a dose threshold (do) below which no defect is detectable : do ⋍ 1013ions/cm2;

the small number of clusters compared to the number of implanted ions [between 1/1000 and 5/1000). This phenomenon has never been observed before for irradiations with metallic ions(2,3).

The most likely interpretation is the creation of microclusters [smaller than 10 Å) due to the presence of rare gas ions.
An HVEM study of interstitial loop growth in nickel
Authors: Kosel T.H.
Published: June 2020

Previous investigators of radiation-induced growth of interstitial loops in nickel have reported observations of rounded Frank loops. Observations of Frank interstitial loops in copper have shown that during growth these loops assume a hexagonal shape with sides lying along <110> directions, due to the splitting of the Frank partial into a Shockley and a stair rod, making jog nucleation more difficult. This splitting should be much less in nickel due to its high stacking fault energy so that jog nucleation should proceed easily, leading to the observed rounded shape. The larger splitting of perfect dislocations should make jog nucleation on perfect loops more difficult than on dissociated Frank loops.

In the present work, the observation of rhombus shaped perfect loops growing near rounded Frank loops (Fig. 1) can be explained by the above reasoning. However, the occurrence of a low jog density growth form does not necessarily imply a large departure from diffusion controlled climb rates.
Depth distribution of cavities in 20- and 500-KeV4 He+-irradiated nickel
Authors: Das S. K. , Fenske G. , Kaminsky M.
Published: June 2020

Studies on depth distribution of damage and of cavities (voids and bubbles) in ion irradiated metals are of importance for an understanding of the mechanisms of radiation blistering and are of general interest to the field of radiation damage.The present paper describes transmission electron microscopy results on depth distribution of cavities and of dislocation damage in nickel irradiated at 500°C with 20- and 500-keV 4He+ ions. The results are compared with calculated projected range and damage energy distributions.

High purity (99.995%) annealed polycrystalline nickel foils were irradiated at 500°C with either 20- or 500-keV 4He+ ions to total doses of 2.9 x 1016 and 1 x 1017 ions/cm2, respectively. Thin foils suitable for transmission electron microscopy were prepared from the irradiated samples by a transverse sectioning technique described elsewhere, which allows one to obtain depth distribution of damage and of bubbles from a single specimen.

Figure 1 shows typical bright field transmission electron micrographs of the plated and irradiated regions of annealed polycrystalline nickel irradiated at 500°C with 500-keV 4He+ ions to a dose of 1 x 1017 ions/cm2.