bluuebunny/crossref_metadata_2025 huggingface dataset:
Is there a “universal” MAC equation?
Authors: Ogilvie Robert E.
Published: June 2020

The search for an empirical absorption equation begins with the work of Siegbahn (1) in 1914. At that time Siegbahn showed that the value of (μ/ρ) for a given element could be expressed as a function of the wavelength (λ) of the x-ray photon by the following equation

where C is a constant for a given material, which will have sudden jumps in value at critial absorption limits. Siegbahn found that n varied from 2.66 to 2.71 for various solids, and from 2.66 to 2.94 for various gases.

Bragg and Pierce (2) , at this same time period, showed that their results on materials ranging from Al(13) to Au(79) could be represented by the following

where μa is the atomic absorption coefficient, Z the atomic number. Today equation (2) is known as the “Bragg-Pierce” Law. The exponent of 5/2(n) was questioned by many investigators, and that n should be closer to 3. The work of Wingardh (3) showed that the exponent of Z should be much lower, p = 2.95, however, this is much lower than that found by most investigators.
Eds Of Radioactive Particles By Self-Induced Fluorescence
Authors: Finch Gregory L. , Cuddihy Richard G.
Published: June 2020

The elemental composition of individual particles is commonly measured by using energydispersive spectroscopic microanalysis (EDS) of samples excited with electron beam irradiation. Similarly, several investigators have characterized particles by using external monochromatic X-irradiation rather than electrons. However, there is little available information describing measurements of particulate characteristic X rays produced not from external sources of radiation, but rather from internal radiation contained within the particle itself. Here, we describe the low-energy (< 20 KeV) characteristic X-ray spectra produced by internal radiation self-excitation of two general types of particulate samples; individual radioactive particles produced during the Chernobyl nuclear reactor accident and radioactive fused aluminosilicate particles (FAP). In addition, we compare these spectra with those generated by conventional EDS.

Approximately thirty radioactive particle samples from the Chernobyl accident were on a sample of wood that was near the reactor when the accident occurred. Individual particles still on the wood were microdissected from the bulk matrix after bulk autoradiography.
A Study Of Diffusion Zones With Electron Microprobe Compositional Mapping
Authors: Marinenko R. B. , Bright D. S. , Handwerker C. A. , Mecholsky J. J.
Published: June 2020

Digital compositional mapping with the electron microprobe has been used to study diffusion zones at metal-metal and metal-glass interfaces. Image enhancement techniques and concentration-histogram images (CHI’s) have been used with these digital maps to improve visual display and interpretation of the movement of elements in these zones.

Metal-Metal Interface. In figure la is a WDS concentration map of gold taken from a specimen of a gold sheet about 40 μm wide sandwiched between two platinum sheets. This specimen was observed as part of a metallurgical study of some ancient Ecuadorian artifacts to better understand the original reaction/diffusion zone between these two metals. The specimen was annealed at 1350°C for 3 min. and then rapidly cooled. This temperature was sufficient to melt the gold (M.P. 1064°C) but not the platinum (M.P. 1769°C). The map in figure la shows that some platinum has diffused into the gold region, but the extent of diffusion is difficult to see in this original grey-level image.
Characterization of occurence and distribution of invisible gold in ore by EPMA
Authors: Mao Shuihe
Published: June 2020

Owing to the invisibility of ultramicron gold (invisible gold) in “Carlin type” gold ore, it is extremely difficult to investigate its occurrence and distribution by conventional determinative means.EPMA has been proved to be very powerful instrument for doing research on this subject because it has advantages of high space resolution, nondestructive,getting quantitative analysis results and observing various kinds of images continuously with same equipment etc.

The unoxidized ore sample is selected from drill cuttings at a “Carl in type” gold mine in Southwest China with gold tenor of 31.02 g/t and weighs 2438g. The operating conditions of EPMA are: accelerating voltage 25kV, beam current 1×10-8 A, beam diameter about 1 μm. AuLα but not AuMα is preferably chosen as analysed x-ray line, because AuMα1 (5.840A) is overlapping with the 3rd order line of FeKα (5.812A) to some extent and iron is the main component of pyrite matrix. According to the expression of detection limit(CDL ), the calculated value of CDL under the circumstances is 0.038%.
Study On The Re-Pentaphosphate Crystal Used As The Standardized Sample For The Electron Probe Analysis
Authors: GuoChuan Fan , Chenting Zhang , Shiji Wanshugen , HongGuangyan YueShuying
Published: June 2020

Fifteen rare-earth pentaphosphates crystals (see table) were prepared by using the evaporation solution method ,which can be used as the standard sample in electron probe quantitative analysis of rare-earth minerals. Chemical analysis has been made for the composition of the samples and theoretic values . According to Boyd’s method,their homogeneity of element distribution and stability under the irradiation of electron beam were carefully invertigated using ModelEMX-SM7 electron probe.The results indicate that under the normal experiment conditions the homogeneity and stability of the samples are qualified. The inconductive samples were also studied to determine the effects of accelerating voltage,electron beam density (diameter of electron beam, beam current),irradiating time of electron beam and the thickness of evaporation film on the sample current and the stability of numbering. The results show that under the normal operating conditions (accelerative voltage 15KV, sample current 2×10-8A ,diameter of electron beam 4-5um)both sample current and numbering are stable within 5 min when the thickness of evaporation film is about 300 .
Individual Coal Flyash Particles Analysis by EPMA
Authors: Sándor S. , Török Sz. , Xhoffer C. , Van Grieken R.
Published: June 2020

Flyash is an extremly heterogeneous particulate material. The morphology and composition of the particles depend on the burning technology and the coal type. Fractionated bulk analysis and individual particle analysis have to be applied to obtain relevant data on the particle formation procedure.

Flyash was sampled in Hungary from 230 MW power station burning third class brown coal mixed with slag. Burning temperature was 1100-1200 C°. A JSM-840 SEM equipped with ORTEC energy dispersive spectrometer was used for morphological studies. Emitted x ray spectra of the particle were measured by adjusting beam settings manually. For automatic particle analysis a JSM-733 superprobe was used with TRACOR particle recognition and characterization (PRC) system. Accelerating voltage was set to 25 and 35 kV and current to 0,3-1.0 nA. In order to detect heavier element traces like As, Rb, Sr and Pb a 100 μm Mo foil was placed into the electron beam. As a result the irradiated area was 2mm in diameter.
Correlative Light, Scanning and Transmission Electron Microscopy of Rat Lungs After Short-Term Exposure to Cadmium Compounds
Authors: Paulini I. , Thiedemann K.-U. , Dasenbrock C.
Published: June 2020

Chronic environmental or workplace inhalation exposure to Cadmium (Cd) compounds may cause lung cancer. The morphological changes induced by short term Cd inhalation exposure have not been investigated. Nevertheless, they might give some insight into the sequence of morphological alterations and the events leading to the development of preneoplastic lesions. In this study, the acute morphological changes in rat lungs due to short term Cd exposure were investigated by correlative light (LM), scanning (SEM) and transmission electron microscopy (TEM).

Rats were exposed to Cd oxide (CdO), Cd chloride (CdCl2), and Cd sulfide (CdS) (270 μg Cd/m3; 18 hrs/d) for 3 d, 9 d, 4 wks, and 4 wks plus 16 wks clean air (recovery groups). Animals were sacrificed 2 d after the end of the exposure period. Lungs were fixed by intratracheal instillation of a 2% glutardialdehyde in Na-cacodylate buffer solution (pH 7.3; 190 mOsmol; 4°C) under a pressure of 20 cm water column and postfixed in 1% Osmium tetroxide (same buffer).
Beam Size in A High-Resolution Ion Microprobe Operated at High Current
Authors: Orloff J. , Swanson L.W. , Li Jia-Zheng , Tuggle Dave
Published: June 2020

In recent years the development of liquid metal ion (LMI) sources has made it possible to produce high intensity focused ion beams - beams with current densities of the order of a few amperes per square centimeter and diameters of from less than 50 nanometers to a few micrometers [1,2]. These beams have been applied in areas such as scanning ion microscopy, surface analysis, lithography, implantation and micromachining (removing minute amounts of material in a precise and programmed way). In terms of technological utility micromachining has been the most important of these applications and dozens of focused ion beam systems are in use around the world, for failure analysis and circuit modification. These latter applications depend on the ion beam for removing minute amounts of material from a surface, inspecting the modified surface and for decomposing metal-bearing gases so as to deposit conducting runs on circuits.

Some of the features of LMI sources that make them so useful for focused beams are: a high angular intensity of 20 microamperes/steradian, typically [3]; a small apparent source size δ of roughly 50 nanometers [4,5]; wide variety of ionic species including Ga, In, Be, Au, Si, As and B (the latter five species requiring a mass-filtering focusing column); great compactness and extremely reliable operation.
Evidence from SIMS of Doubly-Charged Boron Contamination During Singly Charged-Ion Implantation
Authors: Simons D. S. , Chi P. H. , Novotny D. B.
Published: June 2020

When a dopant is introduced into a semiconductor material by ion implantation, it is sometimes desirable to accelerate and implant the ion in a multiply-charged state. This has the effect of increasing the energy and range of the ion without increasing the accelerating potential. Most modern ion implanters are of the pre-analysis type. In this design the ions are first accelerated through a modest extraction potential, e.g., 25 keV. This is followed by deflection for mass-to-charge selection in an analyzer magnet, after which the selected ions undergo final acceleration. Charge-exchange reactions between the doubly-charged ions and residual gas have been found to occur between the analyzing magnet and the final acceleration section. These reactions produce singly-charged ions that receive only half of the energy of the doubly-charged ions during final acceleration. For the case of B++ implantation the resulting implant profile shows a shallow-depth shoulder due to B+, the amplitude of which may be greater than 50% of the main peak.
Transmission Electron Microscopy of Evaporated Perylene Thin Films
Authors: Ewins C. , Fryer J.R.
Published: June 2020

The preparation of thin films of organic molecules is currently receiving much attention because of the need to produce good quality thin films for molecular electronics. We have produced thin films of the polycyclic aromatic, perylene C10H12 by evaporation under high vacuum onto a potassium chloride (KCl) substrate. The role of substrate temperature in determining the morphology and crystallography of the films was then investigated by transmission electron microscopy (TEM).

The substrate studied was the (001) face of a freshly cleaved crystal of KCl. The temperature of the KCl was controlled by an electric heater or a cold finger. The KCl was heated to 200°C under a vacuum of 10-6 torr and allowed to cool to the desired temperature. The perylene was then evaporated over a period of one minute from a molybdenum boat at a distance of 10cm from the KCl. The perylene thin film was then backed with an amorphous layer of carbon and floated onto copper microscope grids.
Three-Dimensional Display of Secondary Ion Images
Authors: Lee J.-J. , Hunter J.L. , Lin W.-J. , Linton R.W.
Published: June 2020

Since the sample surface region is continuously sputtered in dynamic secondary ion mass spectrometry (SIMS), three dimensional (3D) chemical maps can be obtained by acquiring a series of two dimensional (2D) images. Owing to the limitations of the ion beam sputtering technique, SIMS analysis artifacts resulting from factors such as surface roughness, matrix effects, and atomic mixing are present in the 3D volume data. One potential advantage of using 3D display is to provide visual feedback regarding the elimination of artifacts by utilizing correction algorithms as well as correlative information obtained from other surface imaging techniques. In this paper, SIMS 3D maps are displayed by a volume rendering technique in which more information is retained in the image processing steps.

Various 3D display methods have been proposed for SIMS and other microscopic imaging techniques. Some of the previous methods can not display the complete 3D spatial distribution of mass-selected ion intensities.
Electron spectroscopy in SEM and STEM
Authors: Venables J. A. , Hembree G. G. , Harland C.J.
Published: June 2020

Low energy electrons, in the energy range 0-2 keV, are very useful in surface science. Both secondary (0-100 eV nominally) and Auger (50-2 keV) electrons can be used as analytic signals in ultra-high vacuum (UHV) scanning (SEM) and scanning transmission (STEM) electron microscopes. This paper briefly reviews some ongoing projects, which are aimed at improving the spatial resolution and information content of these signals.

Both secondary electron imaging (SEI) and Auger electrons spectroscopy (AES) have a long history. Reviews of AES and its microscopic counterpart scanning Auger microscopy (SAM) have been given previously in this International Conference Series; over the intervening period AES/SAM instruments have become widely available commercially. Simply biassing the sample up to a few hundred volts (-ve) has lead to a new technique (biassed-SEI) which is sensitive at the sub-monolayer level. In general biassing the sample is a useful additional experimental variable. It can be used to visualize thin films and surface topography, including steps; it can also be used to distinguish spectral features (eg Auger peaks) from the sample from those due to stray electrons, and to place such features in the best energy region for the electron spectrometer.
Design of a UHV STEM for Through-The-Lens Electron Spectroscopy
Authors: Bleeker A. J. , Kruit P.
Published: June 2020

Combining of the high spatial resolution of a Scanning Transmission Electron Microscope and the wealth of information from the secondary electrons and Auger spectra opens up new possibilities for materials research. In a prototype instrument at the Delft University of Technology we have shown that it is possible from the optical point of view to combine STEM and Auger spectroscopy [1]. With an Electron Energy Loss Spectrometer attached to the microscope it also became possible to perform coincidence measurements between the secondary electron signal and the EELS signal. We measured Auger spectra of carbon aluminium and Argon gas showing energy resolutions better than 1eV [2]. The coincidence measurements on carbon with a time resolution of 5 ns yielded basic insight in secondary electron emission processes [3]. However, for serious Auger spectroscopy, the specimen needs to be in Ultra High Vacuum. ( 10−10 Torr ). At this moment a new setup is in its last phase of construction.
Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans
Authors: Bradshaw A. M.
Published: June 2020

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).
A Study of DIGM in Ag/Cu system by AEM
Authors: Liu G. X. , Guan Z. M. , Williams D. B. , Notis M. R.
Published: June 2020

DIGM phenomenon is very similar to the diffusion process and the coupled migration of the reaction front occured in discontinuous precipitation. It is likely to postulate that DIGM may occur in the system where discontinuous precipitation appears. W. Kim and co-author have Investigated DIGM In six copper alloy systems (Ag/Cu, Mg/Cu, Sb/Cu, In/Cu, Cd/Cu and Sn/Cu) in which discontinuous precipitation has been found. In Kim s experiment, the diffusion treatments were conducted at 400 °C and 450 °C for 4 days, Kim found DIGM occurred in 4 systems, i. e. Sb/Cu, In/Cu, Cd/Cu and Sn/Cu, but in Ag/Cu and Mg/Cu systems no DIGM was found.

In order to test whether there is DIGM or not in Ag/Cu system, we reexamlned the DIGM phenomenon in Ag/Cu under 400 °C and 480 °C for 5 days diffusion, finally DIGM was found in this system. In different segments of a same boundary the bulging directions and the migration distances may be different as indicated in Fig. 1.
AEM of Ti50Ni40Cu10 Shape Memory Alloys
Authors: Pelton A. R. , Adler P. H. , Yu W. , Holt R. , McConville R.
Published: June 2020

Equiatomic Ni-Ti alloys exhibit shape-memory properties, whereby an article deformed at low temperature regains its original shape at higher temperatures. This effect is due to a reversible martensitic transformation; in binary alloys the parent phase has an ordered cubic (B2) structure which transforms to a monoclinic B19' structure. Substitution of approximately 10% Cu for Ni results in an improvement of shape memory properties which has been attributed to a two-step martensitic transformation from B2 to untwinned B19 and then to twinned B19'. There is, however, some controversy in the literature concerning which phases are in equilibrium and which type of martensite is stable after various thermomechanical treatments. The purpose of this paper is to report on the preliminary findings from an AEM study in order to illuminate the microstructural origins of these controversies.

Ti50Ni40Cu10 alloys were cast in a plasma-arc furnace, sectioned and prepared for scanning and transmission electron microscopy.
Optimized Structure Parameter Determination From CBED
Authors: Marthinsen Knut , Høier Ragnvald , Nils Bakken Lars
Published: June 2020

The application of convergent beam electron diffraction (CBED) for structure symmetry determination is now well established. Application of quantitative CBED in crystal structure studies is so far much less developed. However, the 2-dimensional dynamical intensity distributions in the disks depend strongly on the structure factor magnitudes and phases for the reflections involved. This is particularly the case in the general non-systematic many-beam case where a quantitative determination of structure factor magnitudes and phases from CBED in general has to be based on full dynamical many-beam calculations. It has been shown however that for carefully chosen experimental conditions it is possible to find line intensities which can be analysed on a kinematic basis. The 1-dimensional intensity variation along a systematic row has also been utilized to determine a structure factor phase with high accuracy. However, an optimal use of the CBED patterns should utilize the general 2-dimensional intensity distribution. The number of unknown parameters in a full many-beam simulation will in principle be large, the computer time large even on supercomputers and an effective algorithm for searching in the many-parameter room is therefore highly needed.
Polarity Determination in Sphalerite and Wurtzite Structures
Authors: McKernan Stuart , Barry Carter C.
Published: June 2020

The determination of the absolute polarity of a polar material is often crucial to the understanding of the defects which occur in such materials. Several methods exist by which this determination may be performed. In bulk, single-domain specimens, macroscopic techniques may be used, such as the different etching behavior, using the appropriate etchant, of surfaces with opposite polarity. X-ray measurements under conditions where Friedel’s law (which means that the intensity of reflections from planes of opposite polarity are indistinguishable) breaks down can also be used to determine the absolute polarity of bulk, single-domain specimens. On the microscopic scale, and particularly where antiphase boundaries (APBs), which separate regions of opposite polarity exist, electron microscopic techniques must be employed. Two techniques are commonly practised; the first [1], involves the dynamical interaction of hoLz lines which interfere constructively or destructively with the zero order reflection, depending on the crystal polarity. The crystal polarity can therefore be directly deduced from the relative intensity of these interactions.
Determination of Static Displacements of Atoms by Means of Large-Angle CBED
Authors: Tomokiyo Yoshitsugu , Kuroiwa Takeharu
Published: June 2020

The extinction distance ξ g for electrons becomes large with the increase in an index of excited reflection g. The quasi-kinematical treatment would be applicable if the crystal thickness t is smaller than ξ g/π . When large-angle convergent electron beam is illuminated on a small area of crstal, many reflections may simultaneously satisfy the Bragg conditions and the thickness of the area is considered to be uniform. We can record the intensities of the many reflections on a negative film. If the crystal is tilted so that the high index reflections may fulfill the Bragg conditions, their intensities are sensitive to atom positions in the crystal. In the present paper we will show our recent study on the determination of the static displacement of Al atom in α Al2O3. Our interest is placed on the applicability and accuracy of the quqsi-kinematical treatment.

In αAl2O3 (corundum structure) oxygen atoms ideally form a hexagonal close packed layer and aluminum atoms occupy 2/3 of centers of octahedra formed by oxygen atoms.
Scattering of Quasi-Bloch Wave Sets by a Crystal With Defects
Authors: Borgardt N. I.
Published: June 2020

Application of electron microscopy methods (high resolution electron microscopy (HREM), convergent-beam electron diffraction (CBED)) permitting quantitative information of a defect structure to be obtained causes the necessity of developing a theory of scattering fast electrons by the real crystal.

Determination of the electron wave function by the multislice or real space methods which provide a high accuracy requires numerical calculations for a crystal of a large volume and is restricted to foils with thicknesses of several tens of nanometrs. Effective application of approaches based on the solution of differential equations for amplitudes of diffracted waves or Bloch waves and being widely used for qualitative description of images with a diffraction contrast, is possible only in combination with a column approximation. This approximation, however, is not sufficient for a quantitative analysis, nor is it enough for interpretation of images and diffraction patterns obtained under CBED conditions.

In the present paper, formalism of the Bloch waves is generalized by introdusing the idea of quasi-Bloch wave sets.
Micromorphological Studies on Flux Grown RFeO3 (R = Dy, Ho) Crystals Using SEM and EDAX Techniques
Authors: Kotru P. N. , Kachroon S. K. , Razdan A. K. , Wanklyn B. M.
Published: June 2020

Results are presented of microtopographical studies on rare-earth orthoferrite RFeO3 (R = Dy, Ho) crystals by scanning electron microscopic and energy-dispersive x-ray analytical (EDAX) techniques. The flux growth yields crystals with habit faces. These crystals are therefore suitable for surface structural studies.

The crystals of RFe03 (R = Dy, Ho) are grown from starting compositions of R203, Fe203 (solute), Pb0, PbF2 (solvent), and B203 (additive) in a platinum crucible; the growth procedure has been reported previously. Figures 1 and 2 illustrate platinum deposits on an HoFe03 surface. The modification of advancing growth fronts by an imperfection on an HoFe03 surface is illustrated in Fig. 3.

X-ray mapping and elemental line profiles taken across some peculiar structures on an RFe03 crystal indicate that the areas covered by the structures are rich in R but deficient in Fe. Almost the same observations were made on DyFe03 crystals. It is concluded that use of PbO-PbFe2-B203 flux systems for the growth of RFe03 (R = Dy, Ho) results in the precipitation of magnetoplumbite (PbFe12019) and R0F.
The Analyses of Anthropogenic Atmospheric Particulates by EM
Authors: Russell Philip A.
Published: June 2020

This presentation will summarize fourteen years of research on the physical and chemical nature of particulates suspended in the earths atmosphere utilizing scanning electron microscopy and, to a lesser extent, transmission electron microscopy. Topics to be discussed include (1) the rationale for using electron microscopy to study airborne particulates, (2) methods for collecting airborne particulates, (3) methods of analysis and (4) a summary of results. Examples will demonstrate how conclusions about the nature and source of collected particles can differ between bulk sample analyses and discrete particle analyses. Without the input from discrete particle analyses, bulk analytical techniques may produce serious errors in the apportionment of airborne particulates to specific sources.

The scanning electron microscope (SEM) and transmission electron microscopy (TEM) have proven themselves to be the preferred instruments to use in the study of discrete fine particles because they permit sufficient resolution and analytical capabilities to examine the structure and chemistry of individual particles less than a few micrometers in diameter.
Lens-field axis alignment: a new objective lens alignment for high-resolution Electron Microscopy
Authors: Ishizuka K. , Shirota K.
Published: June 2020

Accurate alignment of an electron microscope is important when the highest achievable resolution is demanded. In a conventional alignment for high-resolution electron microscopy, the incident beam direction is aligned for the object point imaged at a viewing-screen center. It should be noted however that the object point corresponding to the viewing-screen center does not usually located on the magnetic-field axis of an objective lens due to lens misorientation and/or beam deflection caused by a leakage field around the objective lens. Then, the voltage-center and coma-free conditions cannot be satisfied simultaneously, even if a magnetic-field is rotationally symmetric. We implemented last year a proposed scheme to satisfy both coma-free and voltage-center conditions. This alignment scheme however requires a suitable deflector at the objective image plane.

In this report, we summarize ordinary alignment procedures for high resolution electron microscopy and propose a new alignment procedure, which we call a lens-field axis alignment. Using this alignment we can satisfy the coma-free and voltage-center conditions simultaneously.
Computer control of Transmission Electron Microscopes possibilities, concepts and present limitations
Authors: Völkl E. , Allard L.F. , Dodson T.A. , Nolan T.A.
Published: June 2020

The electron microscope laboratory at the High Temperature Materials Laboratory in Oak Ridge National Laboratory runs essentially film free. This is possible due to the use of TV-rate and slow-scan CCD cameras together with fast desktop computers connected through Ethernet to network servers for image storage and a variety of hard copy output devices. In our experience, the functionality of a film-free laboratory goes beyond the simple replacement of film material with some other storage media. For example, the tim and effort to produce a final hardcopy image has been reduced effectively from several hours to several minutes. At the same time, data accuracy has increased due to the high linearity of the CCD cameras and data safety is improved due to automated nightly backups.

The present all-digital setup of our TEMs has already changed the routines on how an TEM is run. Two si uations occur regularly: 1) one microscopist moves back and forth between the TEM and the computer and 2) two microscopists run the computer and/or TEM as a team. Unfortunately, the tasks of recording an image and running the microscope are still very much separated.
High-resolution measurement of birefringent fine structure in living cells using a new polarized light microscope
Authors: Oldenbourg Rudolf
Published: June 2020

The recent renaissance of the light microsope is fueled in part by technological advances in components on the periphery of the microscope, such as the laser as illumination source, electronic image recording (video), computer assisted image analysis and the biochemistry of fluorescent dyes for labeling specimens. After great progress in these peripheral parts, it seems timely to examine the optics itself and ask how progress in the periphery facilitates the use of new optical components and of new optical designs inside the microscope. Some results of this fruitful reflection are presented in this symposium.

We have considered the polarized light microscope, and developed a design that replaces the traditional compensator, typically a birefringent crystal plate, with a precision universal compensator made of two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at ALL POINTS of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen.
3-D optical transfer in excitation field synthesis microscopes
Authors: Krishnamurthi Vijay , Bailey Brent , Lanni Frederick
Published: June 2020

Excitation field synthesis (EFS) refers to the use of an interference optical system in a direct-imaging microscope to improve 3D resolution by axially-selective excitation of fluorescence within a specimen. The excitation field can be thought of as a weighting factor for the point-spread function (PSF) of the microscope, so that the optical transfer function (OTF) gets expanded by convolution with the Fourier transform of the field intensity. The simplest EFS system is the standing-wave fluorescence microscope, in which an axially-periodic excitation field is set up through the specimen by interference of a pair of collimated, coherent, s-polarized beams that enter the specimen from opposite sides at matching angles. In this case, spatial information about the object is recovered in the central OTF passband, plus two symmetric, axially-shifted sidebands. Gaps between these bands represent "lost" information about the 3D structure of the object. Because the sideband shift is equal to the spatial frequency of the standing-wave (SW) field, more complete recovery of information is possible by superposition of fields having different periods. When all of the fields have an antinode at a common plane (set to be coincident with the in-focus plane), the "synthesized" field is peaked in a narrow infocus zone.
Visualization of β-sheets and some amino acid side chains in 400 kV electron images of streptavidin crystallized on phospholipid monolayers
Authors: Avila-Sakar Agustín J. , Chiu Wah
Published: June 2020

Two-dimensional (2-D) protein crystallization on lipid monolayers is an emerging technique with potential application to structure elucidation of biological macromolecules (Uzgiris and Kornberg, 1983). Among more than a dozen proteins or macromolecular assemblies which have been crystallized by this technique, streptavidin 2-D crystals diffract electrons beyond 3 Å (Kubalek, et al., 1991), indicating that structural information from them is retrievable to near-atomic resolution. This 15 kD protein, synthesized by Streptomyces avidinii, is probably the single most widely used protein in modern biochemical assays. It forms nearly irreversible complexes (Kd ≈ 10-15 M) with the vitamin biotin and biotinylated molecules, which can be detected by a variety of methods.

2-D streptavidin crystals were grown on biotinylated lipid monolayers by a method similar to that of Kubalek, et al., 1991. They were preserved in vitreous ice for electron cryomicroscopy. Electron images were recorded at 400 kV under flood beam illumination at a dose of 8 e-/Å2. Phases from four micrographs were merged.
Correlating imaging and spectroscopy at atomic resolution in the STEM
Authors: Browning N. D. , McGibbon A. J. , Jesson D. E. , Pennycook S. J.
Published: June 2020

The study of materials by electron microscopy has traditionally been divided into two sub-fields, imaging and microanalysis. While both of these have advanced to the level of atomic sensitivity, a complete characterization of a materials structure, composition and bonding requires a correlation between the two. This correlation has been achieved through the combination of Z-contrast imaging and electron energy loss spectrocopy (EELS) in the scanning transmission electron microscope (STEM). For the highly coherent and convergent probe in the STEM, the scattering to a high-angle detector (40- 150 mrad) shows an intensity which is proportional to the Z2-dependence of the Rutherford scattering cross-section. The resultant "Z-contrast" image, which is generated point-by-point as the probe is scanned over the surface of the specimen, can be described as a simple convolution of the probe intensity profile, P2eff (R), and a specimen object function O(R,t),

This incoherent description of image intensity holds for crystalline materials in zone-axis orientations where dynamical diffraction manifests itself as a columnar channeling effect.
High-voltage Electron Microscopy: Where it is and where it may be going
Authors: Allen Charles W.
Published: June 2020

High voltage TEMs were introduced commercially thirty years ago, with the installations of 500 kV Hitachi instruments at the Universities of Nogoya and Tokyo. Since that time a total of 51 commercial instruments, having maximum accelerating potentials of 0.5-3.5 MV, have been delivered. Prices have gone from about a dollar per volt for the early instruments to roughly twenty dollars per volt today, which is not so unreasonable considerinp inflation and vastly improved electronics and other improvements. The most expensive HVEM (the 3.5 MV instrument at Osaka University) cost about 5 percent of the construction cost of the USA's latest synchrotron.

Table 1 briefly traces the development of HVEM in this country for the materials sciences. There are now only three available instruments at two sites: the 1.2 MeV HVEM at Argonne National Lab, and 1.0 and 1.5 MeV instruments at Lawrence Berkeley National Lab. Fortunately, both sites are user facilities funded by DOE for the materials research community.
A project for on-line remote control of a high-voltage TEM
Authors: Parvin B. , Agarwal D. , Owen D. , O'Keefe M.A. , Westmacott K.H. , Dahmen U. , Gronsky R.
Published: June 2020

On-line microscopy commenced with demonstrations for biological and SEM applications. For materials science, a project has recently been established to provide users of the NCEM with remote online access to a 1.5MeV Kratos EM-1500 high-voltage transmission electron microscope via existing wide area networks. Within this project we are developing and implementing a set of tools, protocols, and interfaces to bring transmission electron microscopy on-line for collaborative research. Initially applied to the Kratos, the project will provide increased utilization of this unique instrument with its heretofore restricted access due to its sensitive components and demand for sophisticated operator skills. Additionally, the project will provide computer tools for capturing and manipulating real-time audio and video signals. These tools will be integrated into a standardized user interface that may be used for remote access to any transmission electron microscope equipped with a suitable control computer.

Dynamic study of a specimen in an electron microscope requires continuous adjustment of specimen position and orientation under the beam, illumination conditions, focus adjustments, and corrections for aberrations, all based upon the video signal coming from the imaging system.
Elemental, chemical, and orientational characterization of easily damageable materials with x-ray microscopy
Authors: Ade H.
Published: June 2020

Many of the transmission x-ray microscopy developments since the late seventies, including the ones at the National Synchrotron Light Source (NSLS), were driven primarily by the potential of x-ray microscopy to image wet and unstained biological samples with low radiation dose. High image contrast between an aqueous environment and carbon based materials can be achieved with photon energies between the carbon and oxygen K absorption edges (290-540 eV). This contrast is based on differences in cross section of the elements oxygen and carbon in this energy range. Going beyond this "elemental" sensitivity, Ade et al. recently demonstrated how chemical (valence) sensitivity can be achieved via the X-ray Absorption Near Edge Structure (XANES) at the carbon K edge. In addition, linear dichroism microscopy can exploit the dependence of x-ray absorption resonances on the bond orientation relative to the linearly polarized x rays. For an application of the latter technique see A.P. Smith et al.
Further advances in orientation imaging microscopy
Authors: Dingley D.J.
Published: June 2020

Orientation Imaging Microscopy, OIM, is a relatively new technique which provides an image of the surface of polycrystalline material in which the grains are distinguished by their orientation differences, by the strain within them and the type of grain boundaries that separate them. The technique evolved from the work of Dingley and Venables on application of electron backscatter diffraction EBSD in the scanning electron microscope. In OIM, electron backscatter diffraction patterns are obtained successively at regularly spaced points on a sample surface. At each point, the diffraction pattern is captured, transferred to a computer and automatically indexed. Crystal orientation and diffraction line width are measured. Recent advances have been concerned with post data collection image processing.

In the following illustration orientation imaging microscopy was used to investigate the microstructure of submicron aluminium, vapour deposited onto single crystal silicon coated with silicon dioxide. The experimental procedure described in reference 2 was adapted using a Philips XL 30 SEM fitted with a tungsten electron gun.
High-resolution and diffraction contrast imaging of linear islands formed during molecular beam epitaxy
Authors: Loretto D. , Ross F. M. , Lucas C. A.
Published: June 2020

There is currently a great deal of interest in the growth and properties of 'one-dimensional' structures. This is motivated by scientific curiosity and by the practical urge to fabricate faster, smaller and more efficient electronic and optical devices. It has recently been reported that under certain conditions linear islands can form spontaneously during growth. In this work we investigate linear CaF2 islands which form on Si during molecular beam epitaxy. By combining low resolution diffraction contrast images from plan-view specimens with high resolution images from cross-section specimens we determine that these islands are extremely uniform in width, can be as narrow as 5 nm, and extend over many 10s of μm. We postulate a mechanism for the formation of these novel features based on surface energy minimization.

The experimental conditions have been reported in detail elsewhere. Briefly, CaF2 is deposited from an effusion cell onto a Si substrate at 700°C in a vacuum of 1010 Torr.
Reflection diffracted beam interferometry (RDBI) applied to the study of surfaces
Authors: Herring Rodney A.
Published: June 2020

Diffracted beam interferometry, DBI, (previously referred to as Convergent Beam Electron Diffraction + Electron Biprism Interferometry, CBED+EBI) which uses an electron biprism to deflect diffracted beams (convergent or parallel) can produce an interferogram between any two beams within the information envelope of the microscope such that the beam's amplitude and phase can be measured and studied. As well, the electron source need not be highly coherent. So far, DBI has been applied only to transmission electron diffraction, although there is no reason why it shouldn't be applicable to all electron diffraction methods including reflection high (low) energy electron diffraction, RH(L)EED and, possibly, back-scattered electron diffraction, BSED, in the SEM for the study of surfaces. DBI has already shown that substantial phase information, such as strain at interfaces and dislocations, compositional gradients and small defect clusters which are on the size scale of the unit cell, are retrievable from its holograms.
Interpretation of secondary electron contrast from negative electron affinity diamond surfaces
Authors: Malta D.P. , Posthill J.B. , Humphreys T.P. , Markunas R.J.
Published: June 2020

Diamond is a wide band-gap semiconductor with many unique physical properties that make it an attractive technological material. One such property is the negative electron affinity (NEA) behavior of the surface when properly terminated with hydrogen or a thin metal layer. The NEA diamond surface exhibits an unusually large secondary electron (SE) yield which is desirable for applications in cold cathode electron emitters of flat panel displays. Examination of NEA diamond surfaces by scanning electron microscopy (SEM) has indicated that a unique mechanism appears to be responsible for the SE contrast in which sub-surface microstructural information is contained. This paper provides a brief interpretation of the origin of SE contrast from the NEA diamond surface.

The electron affinity of a semiconductor surface, χ, is defined by the position of the vacuum energy level, E0, relative to the conduction band minimum, Ec (Fig. la). If χ>0, excited conduction band electrons must migrate to the surface and arrive with sufficient kinetic energy to overcome the surface energy barrier in order to escape into vacuum.
Microstructure and microtexture of a Nb-16%Si (DS) Alloy
Authors: Sutliff J. A. , Bewlay B. P.
Published: June 2020

In-situ composite Nb-Si alloys have been studied by several investigators as potential high temperature structural materials. The two major processing routes used to fabricate these composites are directional solidification and extrusion of arc-cast solidified ingots. In both cases a stable microstructure of primary Nb dendrites in a eutectoid of Nb and Nb5Si3 phases is developed after heat treatment. The Nb5Si3 phase is stable at room temperature and forms as a decomposition product of the high temperature Nb3Si phase. The anisotropic microstructures developed by both directional solidification and extrusion require evaluation of the texture to fully interpret the fracture and other orientation dependent mechanical behavior of these composites.

In this paper we report on the microstructural characterization of a directionally solidified (DS) and heat treated Nb-16 at.%Si alloy. The microtexture of each of the phases (Nb, Nb5Si3) was determined using the Electron BackScattering Pattern (EBSP) technique for electron diffraction in the scanning electron microscope. A system employing automatic diffraction pattern recognition, crystallographic analysis, and sample or beam scanning was used to acquire the microtexture data.
Quantitative CBED: an overview
Authors: Bird D.M.
Published: June 2020

In this abstract I will focus on one particular topic which has widespread relevance in the quantitative analysis of CBED; namely the role of computer simulations of CBED patterns. The basic point is that with modern, high-powered workstations we can perform highly accurate and detailed simulations of all types of CBED patterns from crystals in a relatively short amount of time. Most CBED simulations are based on diagonalisation of the many-beam equations, and, for example, on a DEC Alpha workstation one can perform this calculation on a 150 × 150 matrix (sufficient for a highly accurate simulation in many systems) in around 1.8s. A full, two-dimensional CBED pattern with, say, 50 orientations across each disc (which is a high-resolution simulation) can then be calculated in less than 1 hour. How can such simulations be used in a quantitative analysis of CBED patterns? I will address this by looking at some specific examples covering various aspects of quantitative CBED.
New beam-selection criteria for quantitative convergent beam electron diffraction
Authors: Birkeland C. , Holmestad R. , Marthinsen K. , Høier R.
Published: June 2020

A successful technique of quantitative CBED is the simulation and refinement of intensity linescans taken across energy-filtered CBED-disks recorded with a CCD-camera. Using many-beam dynamical calculations, line-scans simulated theoretically are fitted to the experiment using a least-square fitting procedure. In the present studies, the systematic row method and modified standard software are used. A description of this technique and its use in intermetallic alloys are explained elsewhere. The Bloch-wave method requires diagonalisation of a non-Hermitian matrix and a large number of beams is needed to give accurate results. In practice, the problem is solved using a limited number of beams. The selection criteria used to select these beams are therefore crucial. Too many diagonalised beams in the calculations result in numerical instabilities and very time consuming computations. Very little has been published on this beam-selection problem. Recently suggested criteria are: 1) the proximity to the Ewald sphere (|2KSg|max), 2) the kinematic cut-off criteria used to cut off high order reflections (gmax), and 3) the perturbation strength (|Uh/2KSh|mmin|)- These three criteria are adjusted in order to obtain convergence in the Bloch-wave calculations.
Structure determination of a new metastable Au-Sn phase using convergent beam electron diffraction
Authors: Sleight M.E. , Midgley P.A. , Vincent R.
Published: June 2020

Reports of a new metastable Au-Sn phase led to the investigation of this system by Convergent Beam Electron Diffraction (CBED). A novel growth route was used, in which a single metallic layer of Sn was evaporated onto rock salt and allowed to form a thin oxide layer, before a film of gold was evaporated directly on top. Subsequent in-situ heating in a TEM supplied enough energy to allow solid state diffusion of Sn through the oxide to react with the Au, forming a number of intermetallic phases.

A new tetragonal AuSru phase was found, space group P4/nbm and lattice parameters a=6.63Å, c=5.92Å, and it was proposed that this new phase was isostructural with PtPb4 . Further work described here confinns this structure type and shows how the atomic positions were refined using First Order Laue Zone (FOLZ) reflections within a quasi-kinematic approximation.

Fig. 1 shows a section of the FOLZ at the [001] zone axis of this new Au-Sn phase.