bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing Spatial Resolution for X-ray Microanalysis
Authors: Lifshin Eric , Gauvin Raynald , Wu Di
Published: July 2020

In Castaing’s classic Ph.D. dissertation he described how the limiting value of x-ray spatial resolution for x-ray microanalysis, of about 1 μm, was not imposed by the diameter of the electron beam, but by the size of the region excited inside the specimen. Fifty years later this limit still applies to the majority of measurement made in EMAs and SEMs, even though there is often a need to analyze much finer structures. When high resolution chemical analysis is required, it is generally necessary to prepare thin sections and examine them in an analytical electron microscope where the maximum diameter of the excited volume may be as small as a few nanometers. Since it is not always possible or practical, it is important to determine just what is the best spatial resolution attainable for the examination of polished or “as received” samples with an EMA or SEM and how to achieve it experimentally.
Consistency Checks for X-Ray Microanalysis at Low KV
Authors: Statham Peter J
Published: July 2020

This work proposes a new consistency check total based on measurement of bremsstrahlung intensity which can be used to validate analyses even when concentrations have been normalised to 100%.

If elemental content of a material is unknown, spectral peaks have to be identified, either interactively, or by automatic procedures. When peak overlap is severe (e.g. Si K/ Ta M / W M, Al K/Br L), it is easy for an element to be misidentified or missed altogether and at low beam kV, some elements will not even produce a characteristic line suitable for analysis. When element identification or quantification requires deconvolution of closely spaced lines, minor miscalibration or inaccurate peak modelling produces inaccurate peak area estimates, Ai, instead of true peak areas, Ai*, and consequently inaccurate concentration estimates, Ci*. A common consistency check is to confirm that the analysis total is close to unity:
Cryo-Em of Large Unilamellar Phospholipid Vesicles That Self- Assemble At a Critical Temperature
Authors: Talbot T , Booy F , Leapman R D , Gershfeld N L
Published: July 2020

The mechanism for assembly of membrane lipid bilayers in vivo is generally considered to occur on existing membranes which act as templates for the assembly process. Not presently understood is the source of the membrane template. A thermodynamic theory describing a spontaneous process for assembly of unilamellar vesicles with properties of a critical state (1,2) has been tested in this study. The spontaneous formation of large unilamellar vesicles (LUV’s) from phospholipid components of cell membranes at a critical temperature T* has now been documented by cryo-electron microscope studies using aqueous dispersions of dimyrystoylphosphatidylcholine (T* = 29°C), and the total lipid extracts of E. coli membranes cultured at 32°C (T* = 32°C). The lipids were incubated at temperatures below, at and above the critical temperatures for LUV assembly. in conformity with thermodynamic theory, and other physical measurements that indicate unique bilayer properties exist at T* (3-5), LUV’s are seen to form only at T*.
A Time-Sectioning Cryo-Field Emission SEM (Cryo-Fesem) Study of Film Formation in Structured Latex Coatings
Authors: Ma Yue , Scriven L E , Davis H T , Erlandsen S L
Published: July 2020

Structured latex coatings find such applications as specialty paints, micro- and ultra-filtration membranes, templates for synthesizing inorganic complementary structures, and embedding media for whole-cell based bioreactors. to control well the microstructure and other properties of the final coatings requires understanding the film formation process that transforms a deposited layer of colloidal particles of polymer into a coherent solid coating as it dries, usually in air. This process cannot be visualized by light microscopy techniques when the latex particles are a few hundred down to a few tens of nanometers in size, as is normally the case. Conventional electron microscopy requires too high vacuum for liquid samples to survive. Environmental scanning electron microscopy tolerates modest partial pressure of solvent but is limited to a coating’s top surface and at low resolution. What is needed is to observe the interior of a drying, hydrated coating at nm-resolution. Cryo-SEM is a powerful means of studying microstructure evolution throughout a coating’s thickness in the wet and moist stages of film formation.
Versatile and Inexpensive Specimen Holder for High Angle Azimuth Rotation in a Low Temperature Scanning Electron Microscope
Authors: Wergin William P , Erbe Eric F , Ochoa Ronald
Published: July 2020

Low temperature scanning electron microscopy (LTSEM) avoids many of the artifacts associated with chemical fixation, dehydration and critical point drying. As a result, this technique has had numerous applications ranging from biology to hydrology. Unfortunately, experiments using LTSEM are frequently compromised by the limited sample manipulations that are available on most cryo-stages and by the cost of specimen holders. Whereas the conventional SEM stage enables 360° rotation and tilts as great as 90°, the braids or hoses required for cooling a cryo-stage generally limit rotation to about 30° and tilt to less than 40° from normal. Furthermore, the specimen holders for LTSEM may cost several hundred dollars each, thereby prohibiting experiments that require numerous holders. This study describes an inexpensive specimen holder that solves these problems.

Figure la illustrates a drawing of the specimen holder supplied with the standard transfer device from the Oxford CT 1500 Cryotrans System.
Cryo - Fesem of Subcellular Organisation Using an In-Lens Rod with A Vacuum Transfer System
Authors: Allen Terry , Rutherford Sandra , Bagley Steve , Morrison Bob , Goldberg Martin
Published: July 2020

The recent increase in use of Field Emission Scanning Instruments in biology has shown the potential of these systems for sub-cellular imaging, as they essentially provide transmission EM levels of resolution for surface imaging. in structures lacking inherent contrast in thin sections, such as nuclear pore complexes,(NPC) high resolution surface imaging has provided significant complementary structural information to the macromolecular architecture of the NPC. (Goldberg and Allen, 1996). A series of intermediate structural forms of the NPC during its formation has also been described using FESEM, which would not have been resolvable in TEM.(Goldberg, Weise, Allen, Wilson, 1997). All this work was performed with chemical fixation, dehydration and critical point drying, followed by high resolution Chromium coating. We now are extending these studies to a cryo-preservation approach, mindful of the requirement of rapid freezing to preserve the more labile events of membrane dynamics, and also to circumvent the requirement to expose membranes to organic solvents during conventional dehydration.
Preservation of Articular Cartilage for Electron Microscopy
Authors: ap Gwynn Iolo , Richards Geoffery , Wade Stephen
Published: July 2020

Water makes up 60-80% of the wet weight of articular cartilage. The remaining parts of this tissue are made up of a variety of cells, generally referred to as chondrocytes, and an extracellular matrix of, collagen fibrils (types II, IX and XI), proteoglycans. The collagens and proteoglycans, with associated water, are assembled into a structure that is capable of withstanding considerable loading.

The micro-structure of adult rabbit articular cartilage has been described, based upon ultrastructural studies. The tissue is arranged into zones, mainly based on the general orientation of collagen fibrils (See Figure 1). The collagen framework in the radial zone forms a continuous area of radially oriented and tightly bound collagen fibrils, in which are embedded at regular interval, tubular inclusions of proteoglycans (Figure 2). in rabbit tibial plateau tissue these inclusions have diameter of 1-3 fim and can be continuous from the calcified to the tangential zone.
Cryo-SEM and TEM of High Pressure Frozen Cells - Some Technical Contributions
Authors: Walther Paul
Published: July 2020

Imaging of fast frozen samples is the most direct approach for electron microscopy of biological specimen in a defined physiological state. It prevents chemical fixation and drying artifacts. High pressure freezing allows for ice-crystal-free cryo-fixation of tissue pieces up to a thickness of 200 urn and a diameter of 2 mm without prefixation. Such a frozen disc, however, is not directly amenable to electron microscopic observation: The structures of interest have to be made amenable to the electron beam, and the structures of interest must produce enough contrast to be recognized in the electron microscope. This can be achieved by freeze fracturing, cryo-sectioning or freeze substitution.

The figures show high pressure frozen bakers yeast saccharomyces cerevisiae in the cryo-SEM (Figures 1 and 2) and after freeze substitution in the TEM (Figure 3). For high pressure freezing either a Bal-Tec HPM 010 (Princ. of Liechtenstein; Figures 1 and 2), or a Wohlwend HPF (Wohlwend GmbH, Sennwald, Switzerland; Figure 3) were used.
Negative Stain Electron Microscopy (EM) of Baculovirus Cultureassembled Virus Capsids
Authors: Humphrey Charles D
Published: July 2020

Caliciviruses (CacV) including Norwalk like virus and Sapporolike virus, papillomaviruses (PapV, and parvovirus B19 (B19V) are infectious viruses known to cause a variety of diseases. These viruses are distinctive because of their low titers in body fluids and fastidious nature to culture, making them difficult to detect by EM or serology. The genomes of several CacVs, PapVs, and B19Vs have been characterized facilitating expression of specific proteins via recombinant technologies. Recombinant proteins may be useful for obtaining the antibodies to be used in improved immunoassays and vaccines for preventing diseases associated with these viruses. CDC and Emory University investigators have designed techniques by which capsid proteins for a variety of viruses including CaCV, PapV, and B19V were expressed in Autographies califomicanuclear polyhedrosis virus (AcNPV) infected Spodoptera fruigiperda (Sf9) cells. Those proteins self-assembled into virus-like particles (VLPs)(Figs.l- 4). Culture-expressed capsids were “purified” and concentrated by traditional protein purification techniques including gel filtration, sucrose gradient centrifugation and cesium chloride gradient centrifugation.
Characterization of Novel Yeast Endosome to Vacuole Mutants by Electron and Fluorescent Microscopy
Authors: Pinho M , Gharakhanian E
Published: July 2020

The vacuole of yeast, Saccharomyces cerevisae, is equivalent to the mammalian lysosome. Several genes and gene products have been identified in the vesicular transport of soluble hydrolases to the vacuole via an endosomal compartment. This postendosomal stage of vacuolar trafficking delivering biosynthetic, endocytosed, and autophagic/Cvt cargo specifically to the vacuole remains one of the least defined stages of vesicular transport. We have previously developed an immunological screen for mutants that internally accumulate a pre-vacuolar intermediate of the vacuolar protease, Carboxypeptidase Y (CPY), in a PEP4-independent manner while exhibiting normal secretion phenotypes. We hypothesize that such mutants would be defective at endosome to vacuole step of delivery, hence env mutants. in order to morphologically characterize our novel set of mutants we performed electron, fluorescent and Nomarski microscopy analysis.

Preliminary studies revealed pleiotrophic phenotypes with respect to vacuole structure by Nomarski and fluorescent microscopy. FM-464 uptake and staining assays shows punctate staining throughout the cell in mut79 and mut72.
Low Voltage Scanning Electron Microscopy
Authors: Joy David C , Newbury Dale E
Published: July 2020

Low Voltage Scanning Electron Microscopy (LVSEM), defined as operation in the energy range below 5keV, has become perhaps the most important single operational mode of the SEM. This is because the LVSEM offers advantages in the imaging of surfaces, in the observation of poorly conducting and insulating materials, and for high spatial resolution X-ray microanalysis. These benefits all occur because a reduction in the energy E0 of the incident beam leads to a rapid fall in the range R of the electrons since R ∼ k.E0  1.66. The reduction in the penetration of the beam has important consequences. Firstly, volume of the specimen that is sampled by the beam shrinks dramatically (varying as about E0  5 ) and so the information generated by the beam is confined to the surface of the sample. Secondly, the yield 8 of secondary electrons is increased from a typical value of 0.1 at 20keV to a value that may be in excess of 1.0 at 1keV.
3d Visualization Tools
Authors: Dougherty Matthew T
Published: July 2020

The tutorial presents 3D visualization as implemented at NCMI: beginning with a brief overview of the history and philosophy of scientific visualization, proceeding to a description of general methodologies used throughout the field of visualization, and concluding with specific applications in electron microscopy, confocal microscopy and x-ray diffraction. The majority of the tutorial uses biological examples of visualization to demonstrate concepts and tools.

History and Philosophy: Effective scientific visualization presents data in a simple, accurate conceptual formulation. Over the last one hundred years there has been a sea change in its economics caused by digital computers: beginning with calculated tables that were manually plotted, proceeding to two dimensional image graphics, and most recently multivariate 3D interactive graphics. The capability of scientific visualization has been greatly facilitated by the evolution of computers; particularly over the last ten years the 3D visualization of biological structures is quickly becoming a necessity for analysis, conceptualization, and presentations.
X-Ray Microanalysis of Materials in the ESEM or VP-SEM
Authors: Gauvin Raynald
Published: July 2020

When performing X-Ray microanalysis in the ESEM (Environmental Scanning Electron Microscope) or in the VP-SEM (Variable Pressure Scanning Electron Microscope), the operating conditions of the microscope must be optimized. This is to reduce the beam broadening of the incident electrons when they scatter with the gas molecules before entering into the specimen. As a result of this scattering, the incident beam is composed of two parts. The first part of the beam is the unscattered beam and the second part is the scattered beam, named the skirt. in high pressure and long working distances conditions, the diameter of the skirt may extend to several millimeters. in order to show the effect of the skirt on X-Ray generation, a copper strip was placed.5 mm away of the electron beam on a flat Al specimen. The peak to background ratio of the copper line was measured at different pressure (from 25 to 200 Pa) for Air as gas.
Microcharacterization of Induced Electric Fields in Poorly Conducting Specimens Irradiated in an Environmental Scanning Electron Microscope
Authors: Stevens-Kalceff Marion A
Published: July 2020

In a conventional scanning electron microscope, a thin, grounded conductive coating is applied to specimens that are poor electrical conductors to prevent retarding and deflection of the incident electron beam. in a variable pressure or environmental scanning electron microscope (ESEM), excess charge on the surface of uncoated poorly conducting specimens is balanced using ionized environmental gas. Ionized gas in environmental mode and grounded conductive coatings in conventional or high vacuum mode minimize charging at the specimen surface, however significant charge trapping may still occur in the implanted sub-surface regions of poorly conducting materials. A small fraction (<10-6) of the incident electrons are trapped at irradiation induced or pre-existing defects within the irradiated specimen. The trapped charge induces a highly localized electric field which can result in electro-migration and micro-segregation of charged mobile defect species within the irradiated micro-volume of specimen.
Time Dependent Study of the Positive ion Current in the Environmental Scanning Electron Microscope (ESEM)
Authors: Morgan SW , Phillips MR
Published: July 2020

The Environmental Scanning Electron Microscope (ESEM) is capable of image generation in a gaseous environment at sample chamber pressures of up to 20 torr. in an ESEM, low energy secondary electrons emitted from a sample surface, by virtue of the primary electron beam, are accelerated towards the positively biased metallic ring (typically +30 to +550V) Gaseous Secondary Electron Detector (GSED). As these electrons accelerate towards the ring they undergo ionizing collisions with gas molecules producing positive ions and additional electrons known as environmental secondary electrons. The environmental electrons further ionize the gas on their way to the ring producing a cascade amplification of the original signal. The amplified signal induced in the ring is used to form an image. The electric field generated between the GSED ring and the grounded stage causes the positive ions produced in the cascade to drift towards the sample, effectively neutralizing negative charge build up on the surface of a non-conducting sample.
Teaching Microscopy by Workshop
Authors: Elaine C. Humphrey
Published: July 2020

The Biosciences Electron Microscopy Facility at UBC has at present two TEMs, one SEM, two confocals. several fluorescent light microscopes and an above average amount of digital imaging equipment used p by graduate students. The facility supports the Faculty of Medicine and the Faculty of Science and is run by a Director (myself) with one assistant. It is busy having an average of 600 individual users per year. The only way this number of users can be accommodated is by making them independent of staff. Training students had been previously on a one-to-one basis. This is very time consuming. Four years ago with no full time assistant, I decided to approach training in a different way. We started a confocal microscopy workshop aided by one PhD student.

We run a 1.5 day practical confocal workshop. It is one day as a group, giving the basic concept of confocal microscopy, and using the instrument from “this is how you switch the machine on” to “this is how you deal with the stack of images.”
Integration of Asset Management into a Multi-Instrument, Multi-Platform Microscopy Teaching Facility
Authors: Murphy Judy A
Published: July 2020

In a two year microscopy teaching program which includes 18 microscopy courses, there are thousands of images which must be collected from a variety of input devices running on various platforms. These must then be associated with different types of data files that need to be tagged to reports as well as being tagged to projects and courses. All of this information must be accessible, first to all those involved with doing the project as well as to anyone associated with needing the results. Tracking progress and security issues had to be part of the solution. It was also necessary that all of this take minimum staff time. Thus, we had to not only set up an image database, but truly an asset management system. Although it certainly would be possible to develop one’s own system, we are limited in staff time for such a project, and certainly didn’t want to re-invent the wheel if such a product was commercially available.
Remote Scanning Probe Microscopy and its Uses in Distancelearning and Educational Outreach
Authors: Ong Eddie W , Ramakrishna BL , Glaunsinger WS , Pizziconi VB , Razdan A
Published: July 2020

Abstract: Tele-microscopy has become a very active area of research and development in the 1990s where there was a desire to give researchers better access to expensive and specialized microscopes, breaking geographical and time barriers. Rapid advances in telecommunication, computers, and microscopy technologies make possible the establishment of the World Wide Web and the realization of the goal of developing a “laboratory without walls”. This provides unprecedented opportunities for researchers and educators alike to gain access to shared instrumental and educational resources.

In this presentation, a description of the Interactive Nano-Visualization for Science and Engineering Education (IN-VSEE) project will be given. The primary goals of IN-VSEE are to (i) convey the excitement of nanoscience and nanotechnology to promote studentmotivated learning and pursuit of science and engineering careers, (ii) teach fundamental interdisciplinary concepts in science and engineering using a visual format to help students learn and integrate information more effectively, (iii) provide students with the capability to routinely explore materials in three dimensions with resolutions at the nanoscale and even down to the atomic scale, and (iv) demonstrate the feasibility of remote operation of research-grade laboratory instrumentation for development into a powerful educational and collaborative tool.
Formal and Informal Microscopy Education at the University of Iowa Central Microscopy Research Facility: Project Centered Training
Authors: Nessler Randy , Potter Ryan , Stahl Jodi , Wilson Katina , Moninger Thomas , Moore Kenneth
Published: July 2020

The University of Iowa Central Microscopy Research Facility (CMRF) has been in existence for 27 years. Starting out as a transmission electron microscopy (TEM) research laboratory, the facility has offered formal college courses. These courses require that students identify a project to investigate during the semester. Theory from the formal lecture is reinforced by work performed in the laboratory session. From its modest beginnings, the CMRF has continually grown. Currently, the facility offers two Confocal microscopes, two Scanning Electron Microscopes, a Scanning Probe Microscope, Energy Dispersive Spectroscopy, a Mossbauer spectrometer, a PTI Ion Imaging/Ratio system, a Freeze Fracture apparatus, and three light microscopes equipped with CCD cameras. Techniques range from routine histology to in-situ hybridization. Technological advances over the history of the facility have not been confined to the lab. in the past, most lectures were given using overheads and 35mm slides.
An XML Language Template Design for Managing a Remote Instrument Educational Outreach Project
Authors: Lazarevich A , Carragher B , Potter CS , Weber D
Published: July 2020

For the past two years we have been operating a remote instrument educational project called Bugscope. Bugscope is an educational outreach project that provides access to an environmental scanning electron microscope (ESEM) for K-12 classrooms. While the operational aspects of the project require a minimal amount of staff time, the information management for the project is difficult for a small microscopy research group to support without a significant allocation of resources away from the group’s principal research goals. in an effort to alleviate this problem we have begun, in the past five months, to develop a software toolkit called ‘Information Technology for Outreach Projects’ (ITOP) - using the Bugscope project as a test bed. The goal of ITOP is to make it practical for academic research groups to provide scientific resources for educational outreach projects by automating many of the administrative and data handling tasks.
Digital Imaging: Emerging Technologies
Authors: Mackenzie John M
Published: July 2020

This invited paper will address several emerging technologies that have an impact on scientists moving into digital imaging technology and raise a few concerns about this digital technology that may not have reached our group.

The quality of inkjet printers has moved forward at a staggering rate. The latest printers from Epson (the 900 series) have achieved a milestone in image quality that is very significant and yet is difficult to find in the specification sheet. The “dots” which the company claims can be as small as 3 picoliters are sufficiently small that they cannot be seen with the naked eye. with an improved algorithm, the image quality in 1440 × 720 mode is as good as any dye-sublimation printer. The current 980 when printing in 1440 mode prints at twice the speed as the older 900. At only $250, it actually becomes cost effective to replace 900's with 980's solely based on the amount of time that is saved (even at a University).
Investigation of The Self-Assembly of Chiral Molecules At Liquidsolid Interfaces Using Scanning Tunneling Microscopy Chemical Marker Groups: Driving Forces for 2-D Separation of Chiral Species
Authors: Yablon Dalia , Flynn George
Published: July 2020

Self-assembly of molecules on surfaces is fundamentally a process whereby individual molecules, separated in the gas or liquid phase, fonn ordered arrays on a surface. The driving forces for these self-assembly processes are the attractive and repulsive interactions among the molecules themselves and between the molecular assemblies and the surface. Since physisorption causes minimal perturbation of chemical bonds, studies of physisorbed species provide an extremely convenient method for investigating issues of molecular structure, conformation, orientation and dynamics of molecules in their “natural” state. The two dimensional nature of the interface introduces constraints that can be used advantageously to separate and identify novel structures.

Control and manipulation of self assembly and molecular conformation is one of the key issues often cited in efforts to develop nanotechnology initiatives for the next generation of electrical and mechanical devices. The development of molecular electronic devices based solely on organic materials will also require careful control and manipulation of molecular assemblies as well as the conformations and orientations of the molecules and functional groups within these arrays.
Functional Group Contrast in Scanning Tunneling Microscopy Images of Substituted Phenylethers
Authors: Musselman I H , Kangasniemi K H , M. Lubag A J , Franceschetti J K , Lee H S , Iyengar S
Published: July 2020

Numerous scanning tunneling microscopy (STM) studies of adsorbates at gas/solid and liquid/solid interfaces have been reported. Although early STM experiments of these systems were concerned primarily with visualizing molecules at the atomic level, the focus has shifted to extracting chemical information from STM images, including the identity of atoms or of functional groups within an adsorbed molecule. However, STM image interpretation continues to be an immense challenge and one currently debated issue of critical importance is the mechanism(s) by which the image contrast reveals atomic and molecular structure. Recently, a combination of electronic and geometric factors was proposed. The electronic factor addresses the coupling between the energy levels of the adsorbate and the Fermi level of the surface whereas the geometric factor is related to the spatial overlap between the STM tip and the functional group.

A previous study in our laboratory of a homologous series of para-halogenated phenyloctadecyl ethers (X-POEs, where X = H, CI, Br, I), physisorbed onto highly oriented pyrolytic graphite (HOPG), revealed a bias-dependent contrast in STM images resembling calculated (HyperChem) electron density contours of bonding molecular orbitals.
Proximal Probe Microscopes: tools for Nanotechnology
Authors: Li Xiaomei , West Paul
Published: July 2020

Proximal Probe Microscopes are emerging as powerful tools for facilitating nanotechnology and nanoscience innovations. Probe microscopes operate by moving a nanoscopic probe across a surface in a raster motion. A surface topographic image is generated by displaying on a computer screen the three-dimensional motion of the probe, and hence a three-dimensional rendering of the surface. in addition to providing a standard magnified view of a surface associated with traditional microscopes, proximal probe microscopes provide quantitative height information. The primary factor establishing resolution in a probe system is the diameter of the probe. with recent advances in probe microscope techniques it is possible to measure more than three-dimensional surface profiles. Examples include measuring surface physical and chemical properties, manipulating objects on a surface, and altering surface properties.

In an atomic force microscope the probe is placed in the vicinity of a surface, and various types mechanical properties may be measured. For example, mechanical properties such a surface hardness and elasticity are measured by monitoring the mechanical interactions between the probe and a sample’s surface. in one such method, the probe is vibrated above the surface and the phase and amplitude of the probe’s vibration depends on the mechanical properties of the surface; Figure 1 illustrates this technique.
Noninvasive Probing of Redox Reactions in Single Living Cells by Scanning Electrochemical Microscopy (SECM)
Authors: Mirkin M V , Liu B , Rotenberg S A
Published: July 2020

We reported recently the first application of the scanning electrochemical microscope (SECM) to probe the redox activity of individual living cells. The possibilities of measuring the rate and investigating the pathway of transmembrane charge transfer (CT) were demonstrated. Significant differences were detected in the redox responses given by normal human breast epithelial cells (MCF-10A) and metastatic breast cancer cells (MDA-MB-231). Here, we demonstrate that the intracellular redox potentials and concentrations of redox components in the cell can be evaluated noninvasively by the SECM. Such measurements provide mechanistic explanation of the observed differences in cell redox activities.

In SECM, a microscopic electrochemical sensor, usually called the tip, is scanned over the surface of a sample, and topographic images and maps of chemical reactivity across the surface are obtained. The schematic diagram of such measurements is shown in Figure 1. The oxidized (or reduced) form of redox species initially present in solution reacts at the surface of the ultramicroelectrode tip.
Observation of Magnetic Film Using Magnetic Force Microscope (MFM) in Ultra-High Vacuum (UHV)
Authors: Suzuki K , Kitamura S , Mooney C B
Published: July 2020

In recent years, the magnetic force microscope (MFM) has been used not only for the evaluation of magnetic media but also for the measurement of magnetic characteristics of quantum dots as well as in various fields, because the MFM can visualize magnetic field on the sample surface with the high resolution. The MFM observation in ultra-high vacuum (UHV) requires to reduce the adsorption layer on the sample surface for high resolution observation. The slope detection mode using the variation of vibrating cantilever is basically unstable in UHV due to the increase in the Q factor of the cantilever. Accordingly it has been used for the MFM observation in air. On the other hand, the FM detection technique offers a very high sensitivity because of the high Q factor.

This repot describes the MFM technique to take a magnetic image steadily in UHV. We observed the surface of a magnetic material with MFM technique in UHV, and compared the slope detection technique, the phase detection technique using phase variation of cantilever vibration, and the FM detection technique.
New Automated Analytical Integration for TEM Operation
Authors: Dingley DJ , Mainwaring PR , Sandborg J A , Tiner M , Wright S I
Published: July 2020

Current trends seek to make TEM operation more routine and productive. One of these follows the lead made in scanning electron microscopy in which the spatial distribution of crystallographic data over a selected area of a sample surface is determined by automated recognition of Backscatter Kikuchi patterns (EBSD), Adams et al. This method has been extended to the TEM in a novel manner, Wright et al. Dark field images are collected sequentially from the area of interest for all possible incident beam directions over a solid cone of semi-apex angle up to 4 degrees, Figure 1. The images are recorded directly into a computer. Off line automated analysis follows in which all dark field images are searched to determine the beam conditions under which each pixel in the image brightens, i.e. when the corresponding point in the sample came into a diffraction condition. The measurement of three such non-coplanar conditions for a pixel leads to the determination of the corresponding crystallographic orientation. The accuracy of orientation measurement has been improved to 1 degree by the fitting of the determined diffraction vectors to the surface of the Ewald sphere. The analysis allows grain maps to be reconstructed from which grain size distribution can be automatically determined. Figure 2.
Complete Identification using Spectral Imaging, Compass, and Phaseid
Authors: Camus Patrick P , Dow Audrey A , Rohde David B
Published: July 2020

The complete and accurate identification of all of the phases present in a sample is the ultimate goal of any materials investigator. The identification should include compositional as well as crystalline measurements for unique characterization. in an SEM, the composition of individual regions can be routinely determined via EDS or WDS analysis. The main limitation is the need to visually identify the individual regions from the images alone. A method to limit this restriction is to collect x-ray maps of the field-of-view. This technique has the benefit of providing the spatial distribution of the elemental species, but requires knowledge of all of the elements of interest before the start of the analysis and composition quantification cannot be performed with data only from the maps. Another disadvantage is the possibility that materials may have similar compositional analyses but may be different phases only manifested by crystallographic means.

A better method of complete phase identification involves the collection and analysis of spectral images and the subsequent crystallographic phase identification via EBSD. Spectral imaging consists of the collection of complete EDS spectra at each location within a field-of-view. From this 3-D data set, a series of elemental maps may be extracted for visualizing the spatial distribution of any elements of interest. This data set is especially useful because elements, and even characteristic x-ray lines, can be fully analyzed after the data collection with total flexibility.
Benefits of a Cs-Corrector for Material Science
Authors: Kabius B , Haider M , Uhlemann S , Schwan E , Urban K , Rose H
Published: July 2020

One of the limiting parameters in high-resolution transmission electron microscopy (HRTEM) are the high values for the spherical aberration Cs of the objective lens, which are the reason, that for TEM's with field-emitter the point resolution at Scherzer defocus is about two times lower than the information limit. Another effect of Cs-values of about one mm is the rather large disc of least confusion, which contributes to a high amount of contrast derealization. Furthermore the images are very sensitive towards beam tilt. These disadvantages contribute to a difficult interpretation of HRTEM-images especially at interfaces and defects. In-situ applications as well as diffraction contrast experiments require a gap of at least ten mm between the pole pieces. For the present TEM's this degrades the resolution at an acceleration voltage of 200 kV to approximately 0.27 nm. Cs-correction offers the ability to combine high resolution with a large space for the sample, which can be used for in-situ experiments.

Recently, we have constructed a lens system for Cs-correction based on hexapole lenses for a commercial 200 kV instrument equipped with a field emission gun. This system allows choosing the Cs-value between +2.0 mm and -0.05 mm. The objective lens of the microscope has a Cs value of 1.2 mm resulting in a point resolution of 0.24 nm.
New Ultra-High-Resolution TEM Cameras
Authors: Favia Paola , Hunt John , Joyce David , Mooney Paul , Pan Ming
Published: July 2020

TEM image acquisition is subject to limitations in resolution imposed by the physics of the position-sensitive detection process. in existing on-line digital cameras detection consists of scintillation, image transfer and photon detection by a CCD. Scintillator resolution is governed primarily by the incident beam energy. Material parameters affect the resolution only weakly. Some improvement can be made with a thin transmission scintillator. Still, backscatter of electrons from below can form a noisy background. Optical transfer resolution also has an important effect on overall camera system resolution. Leakage of light within scintillator, between fibers, at interfaces, and the inherent resolution loss due to binning into a finite pixel all contribute to optical resolution loss. This point spread function is narrower than the electron point spread function above 100kV but has an affect at all voltages. Long-range light leakage (psf tail) affects the background noise in diffraction work where there is often a 10e6 ratio between central peak and diffraction spot of interest. Thus, the number of resolved pixels in a TEM image detector is limited by the area of the detector, the effective thickness of the scintillator and the quality of the image transfer.

Gatan has developed several improvements which will address both electron and lightoptical resolution loss.
Alpha-Null Defocus: an Optimum Defocus Condition with Relevance for Focal-Series Reconstruction
Authors: O’Keefe Michael A
Published: July 2020

Two optimum defocus conditions are well known to users of high-resolution transmission electron microscopes. Scherzer defocus is useful in high-resolution electron microscopy (HREM) because it produces an image of the specimen “projected potential” to the resolution of the microscope. Lichte defocus is useful in electron holography because it optimizes sampling in frequency-space by minimizing the slope of the microscope objective lens phase change out to the highest spatial frequency in the hologram, consequently minimizing dispersion. For focal-series reconstruction, the requirement to maximize transfer into the image of high-frequency diffracted beam amplitudes leads to a third optimum defocus condition.

Image reconstruction methods allow the achievement of super-resolution - resolution beyond the native (Scherzer) resolution of the microscope - by correction of the phase changes introduced by the microscope objective lens. One such method is focal-series reconstruction, in which diffracted-beam information obtained at several different focus values is combined. to produce a valid super-resolution result, it is necessary to ensure that every spatial frequency is represented appropriately. Suitable choice of an optimum defocus produces optimum transfer of diffracted-beam amplitudes at any chosen spatial frequency.
1-MV Field-Emission Transmission Electron Microscope
Authors: Tonomura Akira
Published: July 2020

We developed a 1-MV field-emission transmission electron microscope to help in further improving electron holography, Lorentz microscopy, and high-resolution electron microscopy. This microscope is characterized by an electron beam having the highest brightness ever, 2×1010 A/cm2, and by the highest lattice-resolution below 0.5 Å. These two features were attained by minimizing the mechanical vibration of the whole column and by improving the stability of both the electron beam and the high voltage. If the tiny electron source located at the top of the 7-m-high microscope moves by as little as a fraction of the source size, 50 Å in diameter relative to the column, due to mechanical vibration or beam deflection by the AC magnetic fields, the beam brightness will be greatly degraded. If the ripples ΔE of the high-voltage E exceed ΔE/E = 5 × 10−7 /min, then the inherent monochromatic feature of the beam is deteriorated by the increase in energy spread.

Through the preliminary experiments testing the vibration and magnetic shielding of the acceleration tube as well as the high stability of the high voltage, and through the numerical simulations on the vibration modes of the whole column, we were led to the conclusion that the microscope must be separated into three parts that are connected by cables.
Present Concepts and Designs for Gun Monochromators
Authors: Kahl F , Voelkl E
Published: July 2020

The attainable information in transmission electron microscopes is limited today primarily by chromatic aberrations, because the new generation of spherical aberration correctors has practically eliminated resolution limits caused by spherical aberration. If it would be possible to develop an electron source with 0.2 eV energy width, the limitations of chromatic aberrations could be minimized, and techniques like Electron Energy Loss Spectroscopy (EELS) could provide much more detail on the type of bonding between atoms. At present, the main approach to reduce the energy width of present day field emission electron sources is to incorporate a beam monochromator in the electron gun. The challenge for such a monochromator is not only to provide a small energy width of 0.2 eV or less, but also to preserve the brightness of the gun as much as possible at a level of current sufficient for high resolution imaging on a routine basis.

Over the last few years, several different designs for monochromators have been proposed. All designs are based on energy dispersive components which separate electrons of different energies spatially and eliminate the ones with high energy deviation by means of a selection slit.
Focused Ion Beam (FIB): More than Just a Fancy Ion Beam Thinner
Authors: Dravid Vinayak P
Published: July 2020

The potential utility of FIB for routine (and novel) applications has come to forefront recently due to advances in ion optics which now allow formation of focused ion probe of better than ∼10-20 nm containing current density exceeding several A/cm2, with a liquid metal source (typically Gallium). The small ion probe size, coupled with shallow sputtering depth - yet high sputtering yield of ions, has opened several opportunities in machining, lithography and ion-assisted deposition.[1-3] These developments, including automation, multi-specimen stages, cross-compatible specimen holders for FIB/TEM/SEM, use of in-situ electron beam (so-called dual beam), coupled with innovations such as the “lift-off” process[4], have provided an invaluable set of tools for microelectronic defect characterization. However, re-deposition (contamination), ion implantation/damage especially for desirable thinner sections (<∼50 nm) remain major concerns for further applications.

While much of the excitement in TEM community for FIB is due to thin foil specimen preparation (especially in microelectronics), we have been exploiting the site-specific micromachining aspect of FIB beyond specimen preparation for TEM, which is the focus of this contribution. Two broad themes will be presented: One exploits the site-specificity of FIB in making thin sections (including lift-off) at and across localized deformation as in indentation response of micro/nanocomposites. The other involves FIB as a fabrication tool for sputtering/drilling arbitrary shapes and sizes down to 20-50 nm, to enhance functional aspects.
Nanoscale Tomographic Imaging using Focused Ion Beam Sputtering, Secondary Electron Imaging and Secondary Ion Mass Spectrometry
Authors: Hull Robert , Dunn Derren , Kubis Alan
Published: July 2020

As the importance of nano-scaled structures in both science and engineering increases, techniques for reconstructing three-dimensional structural, crystallographic and chemical relationships become increasingly important. in this paper we described a technique which uses focused ion beam (FIB) sputtering to expose successive layers of a 3D sample, coupled with secondary electron imaging and secondary ion mass spectrometry of each sputtered surface. Computer interpolation of these different slice images then enables reconstruction of the 3D structure and chemistry of the sample. These techniques are applicable to almost any inorganic material, at a spatial resolution of tens of nanometers, and fields of view up to (tens of μm).

The FIB instrument used in this study is an FEI 200 with a minimum ion probe diameter < 10 nm, an ion current density ∼ 10 A/cm2, a maximum ion current of 11 nA, and a standard Ga+ ion energy of 30 keV. Our instrument is equipped with a continuous dynode electron multiplies (CDEM) for secondary electron imaging and a quadrupole mass spectrometer for secondary ion mass spectroscopy (SIMS) / element specific mapping. Gallium ions of this energy will ablate any material, with sputter yields typically of order ten, corresponding to a material removal rate of order 1 μm3nA−1s−1.
Three Dimensional Characterization of a Specific Site by an FIB Micro-Sampling Technique
Authors: Yaguchi T , Kuroda Y , Ueki Y , Kamino T , Ohnishi T , Umemura K , Asayama K
Published: July 2020

We have developed an FIB micro-sampling technique to prepare both plan view and cross-sectional TEM specimens from a specific site.

The instruments that were used in this study are the Hitachi FB-2000A FIB system equipped a with micromanipulator unit and an HF-2200 cold field emission 200kV analytical TEM equipped with a scanning attachment allowing both STEM and SEM imaging.

Figure 1 shows a procedure to prepare a micro-sample for either plan view or cross-sectional TEM observation of the specific site. First, the micro-sample for plan view TEM observation is trench milled by using an FIB(Figure 1a). Second, a tip of a micromanipulator W-probe is bonded to the micro-sample with the FIB assisted metal deposition. Then, the micro-sample is lifted out and transferred onto a micro-sample carrier(Figure 1b).
Pre-Thinning for FIB TEM Sample Preparation using the Small Angle Cleavage Technique
Authors: Walck Scott D , Colijn Hendrik , Thompson Greg
Published: July 2020

The Small Angle Cleavage Technique (SACT) can produce samples from brittle and cleavable materials very quickly. It is possible for a skilled person to produce about 10 XTEM specimens in an hour. However, there are materials related limitations to the technique. These include 1) the ductile/brittle nature of the substrate, i.e. the fracture mechanics of the materials, 2) the strength of the interfaces between multi-layers, 3) the thickness of any ductile layers, and 4) the strength of the layer materials. in most of the cases where SACT fails, the sample is near electron transparency at the apex of the sample. Where there is a weak interface as in some multi-layer systems, or where the material itself is weak such as when an evaporated Ge layer is used, some of the film near the substrate is sufficiently thin, but there is a jog in the film stack and further back from the apex it is not transparent. If such a SACT sample is viewed from the surface in an SEM, this apparent delaminating of the top layers is evident and usually within 1 μm of the apex.

The purpose of this paper is to show that the geometry of a SACT-prepared sample is well suited for applying FIB milling for further thinning of the sample to electron transparency. in addition, the FIB can be easily applied to SACT specimens that fail to produce usable samples for the reasons cited above. The SACT method allows two main options for mounting the samples that are illustrated in Fig 1.