bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Measurement of Sarcoplasmic Reticulum Calcium Content Following Isoproterenol or Caffeine Treatment
Authors: Sweet Wendy E , Moravec Christine S
Published: July 2020

The major storage site for calcium in cardiac muscle is the sarcoplasmic reticulum (SR). It has been shown using indirect methods that the amount of calcium stored in the SR can be altered by various agonists and anesthetics. The only technique to date which directly quantifies the amount of calcium in the SR is Electron Probe Microanalysis (EPMA). Using EPMA, an accurate measurement of the size of the SR calcium store can be made following treatments with known agonists.

Isoproterenol (ISO) causes an increased inotropic response in cardiac muscle via the (3-adrenergic pathway. When ISO binds to the (β-receptor on the plasma membrane, it causes the activation of Protein Kinase A (PKA) through a cascade of events. PKA phosphorylates the sarcolemmal calcium channels causing an increase in the rate of calcium influx. PKA also phosphorylates Tnl, which sensitizes the myofilaments to calcium, thereby increasing the rate of calcium release from the myofilaments.
Subcellular Composition Based On Light-Element EELS
Authors: Leapman RD
Published: July 2020

Recent work on biological electron energy-loss spectroscopy (EELS) in the analytical electron microscope has focused on measuring concentrations of the important elements, calcium and phosphorus. Analysis of the light elements, for which EELS was originally thought to be best suited, has so far not yielded much useful information from biological specimens. Whereas low-loss fine structure has been analyzed successfully to measure distributions of water and protein in frozen-hydrated cells, core-edge fine structure cannot be recorded at sufficiently low dose to obtain useful chemical information. However, the atomic ratios of the light elements (carbon, nitrogen and oxygen) obtained from EELS are less dependent on electron dose. Together with sulfur (in proteins) and phosphorus (in nucleic acids, phospholipids and phosphates) these ratios can help determine the types and proportions of compounds that are present at the subcellular level. Here we re-examine the potential for making these kinds of measurements.
Can the Number of D Electrons in Transition Metals be Measured from White Lines?
Authors: Rez P
Published: July 2020

Sharp peaks at threshold are a prominent feature of the L23 electron energy loss edges of both first and second row transition elements. Their intensity decreases monotonically as the atomic number increases across the period. It would therefore seem likely that the number of d electrons at a transition metal atom site and any variation with alloying could be measured from the L23 electron energy loss spectrum. Pearson measured the white line intensities for a series of both 3d and 4d transition metals. He normalised the white line intensity to the intensity in a continuum region 50eV wide starting 50eV above threshold. When this normalised intensity was plotted against the number of d electrons assumed for each elements he obtained a monotonie but non linear variation. The energy loss spectrum is given by

which is a product of p<,the density of d states, and the matrix elements for transitions between 2p and d states.
High Resolution X-Ray Microanalysis of Nb/Al Multilayer Thin Films
Authors: Lucadamo G , Watanabe M , Barmak K , Williams D B
Published: July 2020

A study of reactive phase formation in thin films requires the understanding of the thermodynamics and kinetics of the reactions. Previous investigations of phase formation in Nb/Al multilayers using calorimetry and x-ray diffraction have observed that despite the presence of rather large driving forces for phase formation, a pronounced nucleation event occurs. This behavior has been reported in other systems including Ti/Al and Ni/Al. The initial nature of the interface can affect the nucleation, therefore careful studies of the structure and composition of the initial interfacial region may explain the reason for a kinetically separated nucleation and lateral growth step preceding normal phase growth. In addition, examination of the interface may also lend insight into the effects of different deposition processes and can provide evidence for the formation of solid solutions or compounds that can lower driving forces available for phase formation. Finally, the cross-sectional multilayer sample provides a means of characterizing spatial resolution and isolating specimen preparation artifacts.
Detection of small amounts of Fe and Nb in Zr-2.5wt%Nb pressure tubes
Authors: Müllejans H , Thomas J , Kienzle O , Griffiths M , Rühle M
Published: July 2020

The distribution of Nb and Fe in Zr-2.5wt%Nb pressure tube alloys has been of interest, in particular the effects of neutron irradiation. Both Fe in the β-phase and Nb in the α-phase are present in levels below lwt% and fluctuations of these elements in different parts of a specimen or between different specimens are of interest. In EDS quantification the signal-to-noise ratio and hence the detection limit is determined by the signals but depends also on the data analysis, in particular the background subtraction procedure. Here we compare the noise as given by the commercial analysis software to a simple estimate based on counting statistics. We used a VG HB 501 UX equipped with a thin window HP Ge detector, digital pulse processor and Voyager 3105 data acquisition and analysis system (Noran).In the past artefacts of Fe, Ni and Cu had been observed in EDS spectra, even for materials which did not contain any impurities of these elements.
Imaging of Metallic Nano-Particles Using PlasmOn/Valence Energy Loss Electrons
Authors: Hunt EM , Wang ZL , Evans ND , Hampikian JM
Published: July 2020

Although crystal lattices can be determined reasonably well using high-resolution electron microscopy, determination of local chemistry at high spatial-resolution remains a challenge. An energy-filtering system has made it possible to perform chemically sensitive imaging in a transmission electron microscope (TEM). This type of imaging usually relies on the signal of the inner shell ionization edge, the intensity of which is affected by the threshold energy-loss and the ionization cross-section of the edge. Therefore, the spatial resolution of a core loss image image is strongly affected by the signal-to-noise ratio. In this respect, lower loss electrons from the plasmon or valence region of the energy loss spectrum (10-100 eV) are favorable for chemically sensitive imaging due to the much higher signal intensity, provided any delocalization effects are small in comparison to the required spatial resolution. Compositionally sensitive imaging using the aluminum plasmon energy-loss electrons has been shown to produce ∼2nm resolution for an atomically sharp Al/Ti interface.
Computer-Aided Analysis of Oriented Crystallites by Diffraction Pattern Simulation and Tilt-Stage Control in a TEM
Authors: Thomas LE , Chariot LA , Stanley JT
Published: July 2020

Electron diffraction patterns taken in the transmission electron microscope (TEM) provide information about crystal structures and orientations in small sample areas. Extracting this information and manipulating local crystal orientations has become a great deal easier with the availability of desktop computer programs that allow simulation matching of experimental patterns and crystallographic control of sample tilting in the TEM. This presentation will illustrate an application of computer-aided crystallography for analyzing oriented crystallites in an experimentally complex material.

The surface corrosion films that form on reactive metals such as hafnium or zirconium in hot water provided our example. Cross-sectional examinations of the corrosion films revealed a columnar microstructure of monoclinic HfO2/ZrO2 grains extending normal to the metal/corrosion-film interface.The columnar grains were only about 50 nm in width, and thus were too small to analyze individually by selected-area diffraction. Local strains in the films smeared the diffraction fine structure so there was little hope for analysis by convergent-beam diffraction methods.
Is it Really that Easy to Solve Surface Structures Using Direct Methods?
Authors: Marks L D
Published: July 2020

A basic problem in surface science is that, unlike bulk materials, very few of the atomic scale structures are known despite many years of effort. Even the advent of STM has not helped that much since it is difficult to impossible to interpret images without a-priori information. Transmission electron diffraction (or x-ray diffraction) data from surfaces represent a unique opportunity for the application of Direct Methods to solve surface structures, opening up new avenues for science. Diffraction from a surface when the bulk is only weakly dynamical is at least 90% kinematical, but it may be the case that strong (surface) scattering is buried under bulk reflections including the lxl or “surface forbidden bulk-allowed” reflections. In addition, further out in the diffraction pattern subsurface relaxation effects become very important, and these cannot be considered using conventional Direct Methods; instead of sharp atomic-features the true exit wave will have small positive/negative dipoles.
The Pseudo-Atom Approximation in Direct Phase Determination of Protein Structures.
Authors: Dorset Douglas L
Published: July 2020

In principle, the availability of high-resolution micrographs in electron crystallography is a direct solution of the phase problem that has been used to great advantage for the study of proteins. However, as the resolution of the determination increases, the Fourier transform of the micrograph becomes a less accurate phase source. Hence, alternative direct methods for phase determination have been evaluated, if only to extend the resolution of most reliable lower resolution phases to the limit of the electron diffraction pattern. The first demonstration of its feasibility was published in a study of bacteriorhodopsin extending 15 Å image phases to beyond 3 Å by maximum entropy and likelihood procedures i. Later studies demonstrated that convolutional methods also can be effective.

In protein crystallography, there is always an interest in carrying out a true ab initio determinations, if only because of the challenge to traditional direct methods that become statistically less reliable as the number of atoms in the unit cell increases.
New Strategy for Crystallographic Reconstruction of Biological Bundle-Like Structures
Authors: Sherman MB , Jakana J , Sunt S , Matsudaira p , Chiu W , Schmid MF
Published: July 2020

The acrosomal bundle is an intracellular quasi-crystalline organelle in the head of the sperm of Limulus polyphemus. It is a long (up to 60 μm) straight bundle ∼1000 Å in diameter1 consisting of two major proteins in a 1:1 stoichiometric ratio: actin (42 kDa) and scruin (102 kDa) with a minor calmodulin-like protein (14 kDa) presumably bound to scruin molecule. Previous helical reconstructions of single filaments in the bundle showed actin-scruin interactions. We recorded tilt series from single bundles in a 400 kV cryomicroscope and have developed a novel crystallographic technique to reconstruct a unit cell from the bundle as a whole to reveal interfilament interactions.

Acrosomal bundles were purified as described elsewhere and embedded in vitreous ice over holes on a holey carbon film. Tilt series images were collected in a JEOL 4000EX electron cryo-microscope at 400 kV using 10,000x microscope magnification. Total dose was ∼16-18 electrons/Å per series covering a tilt range of ± 60° with 5° angular increment.
Demonstration of Solid State Electron Optical Devices: Pixelated Fresnel Phase Lenses
Authors: Ito Y , Bleloch AL , Brown LM
Published: July 2020

The ability to produce features of nanometer scale offers the possibility of phase manipulation of electron waves. The first conclusive results of phase manipulation by nanometer-scale diffraction gratings directly cut by the finely focused electron beam in a scanning transmission electron microscope (STEM) have already been demonstrated. This was achieved by using a grating with a “wedge” profile. This produced an asymmetrical diffraction pattern (in violation of Friedel's law). This violation is expected only if the grating acts mostly as a strong phase object. In this paper, a demonstration of solid state Pixelated Fresnel Phase (PFP) lenses for electrons will be presented. An array of these electron lenses can be easily formed and may be utilized, for example, as compact electron-beam forming lenses for parallel electron beam lithography.

In general, an incident plane wave traveling along the optic axis of a lens experiences a phase shift. A conventional Fresnel phase lens, consisting of concentric zones with a modulo of 2π phase structure, focuses an incoming electron plane wave to its focal point.
Determination of Tilt Parameters in Electron Diffraction Patterns of 3D-Microcrystals
Authors: Dimmeler E , Holmes KC , Schröder RR
Published: July 2020

Electron crystallography of thin three-dimensional (3D) protein crystals requires very exact determination of tilt angles and spot profiles to obtain correct merging of diffraction spot amplitudes. The reciprocal lattice of 3D microcrystals consists of ellipsoidal spot profiles which are very extended in the direction normal to the crystal face (z*). To extrapolate from the intensity measured in a section to the total spot intensity, two features need to be known very exactly: 1. the orientation of reciprocal lattice relative to the Ewald sphere, 2. the 3D-shape of the spot cloud.

Fig. 1 shows a tilt series of one frozen hydrated catalase crystal, in the order of recording. The third diffraction pattern gives the highest resolution because it is untilted and therefore the electrons have the shortest path length. In the current experimental data taken at 120 keV electron energy inelastic scattering within the crystal leads to a dramatic loss of elastic information in highly tilted patterns.
Determination of Atomic Positions in SiC 4H Using Quantitative Convergent Beam Refinements
Authors: Holmestad R , Morniroli J-P , Zuo JM , Spence JCH
Published: July 2020

Silicon carbide (SiC) is a widely used ceramic material, with many structural and electronic applications. It exists in many polytypes, differing from one another only by the stacking sequence of close packed double layers of Si and C atoms. The polytype called 4H has the hexagonal structure shown in figure 1. The double layers here have a stacking sequence of ABACABAC.. The distance z between the Si and the C layers (shown in figure 1) is an adjustable parameter, which is not exactly known. The aim of this work is to determine the atomic positions in the c-direction by quantitative convergent beam electron diffraction (QCBED). The goal is to develop a general refinement approach for structure determination by electron diffraction. Many newly synthesized materials are available in only very small quantities in the single crystal form and/or mixed with other phases, making X-ray diffraction methods difficult. SiC is often full of stacking faults. For these types of materials, the CBED method is ideal because of the small probe that can be used; areas of less than 100 Å can be studied.
(Under)Graduate Teaching Using Internet Access to Electron Microscopes
Authors: Voelkl E , Allard LF , Bruley J , Williams D B
Published: July 2020

The Lehigh University is presently offering direct access to top of the line electron microscopes at ORNL via the Internet for one graduate and one undergraduate course (Advanced TEM, Electron Microscopy & Microanalysis). The students at Lehigh have the opportunity to themselves control the Hitach HF-2000 FEG TEM. The controls presently include change of magnification and focus, moving the sample and correction for astigmatism. In this way, the students can collect high resolution lattice images of various materials and study e.g., the effects of changing focus on lattice images (contrast reversal). While the students at Lehigh can sit in the class room and run the instrument in broad daylight and communicate freely without disturbing the instrument by phonics, the instrument itself is protected from misuse through several layers of hardware and software.

This new way of teaching EM courses has become possible through recent advances in computer hardware (live-time Fourier transforms (FFTs)) and software. A commercial software package TimbuktuPro provides remote access to the computer at the HF-2000 at ORNL which controls the instrument as well as the slow-scan CCD-cameras (Gatan, model 794) attached to the instrument.
Database of Electron Microscope Images on the World Wide Web
Authors: Taniyama A , Shindo D , Hiraga K , Oikawa T , Kersker M
Published: July 2020

Recently, new recording devices, such as the Imaging Plate and a slow scan CCD camera, have come into wide use for digitally recording and storing transmission electron microscope images. A digital image has advantages of transferring, sharing and storing data. Furthermore the improvement of world wide computer network systems, for example, Internet makes it easier to transfer and share digital data among researchers. We have studied the processing and a quantitative analysis of digital high-resolution transmission electron microscope (HREM) images by means of a standard EWS and an SX-3 super-computer on the intelligent computer network system in Tohoku University, which is called Super TAINS (Fig. 1). With the increase of digital HREM images, we are in need of tools to help us store and quickly search these data.

A web site called “EMILIA (Electron Microscope Image Library and Archive)” was established in October 1996 as a database of HREM images. EMILIA is implemented by a WWW server on Super TAINS and HTML documents. Figure 2 shows sample pages from EMILIA.
Computational Methods for High Resolution Analysis of Cryo-Electron Micrographs of Hepatitis B Virus Capsids
Authors: Conway JF , Cheng N , Zlotnick A , Wingfield PT , Stahl SJ , Steven AC
Published: July 2020

Cryo-electron microscopy allows high resolution structural studies of macromolecules or macro-molecular complexes. As structural analyses extend to higher resolutions, several major compu-tational problems arise in analyzing cryo-electron micrographs. One is the acute sensitivity of the sample to radiation damage, requiring that images be acquired at a low electron dose with conse-quently low signal-to-noise ratio (SNR), especially at higher spatial frequencies. Secondly, as the size of each digitized image grows, the duration of the computational procedures lengthen consider-ably. A third problem is the complex distortion imposed upon the images by the contrast transfer function (CTF) of the electron microscope. We have addressed these issues in the context of solving the Hepatitis B Virus (HBV) capsid structure, and have succeeded in improving the resolution of our model from 17À[4] to 9À[1] (Fig.l). This is sufficient to define part of the molecular structure, including a 4-helix bundle at the dimer interface which constitutes the protruding ‘spike’ domains seen on the surface of the capsid, as well as other helices elsewhere in the molecule.
Computational Advances and Enabling Technologies for 3D Microscopies in Biology
Authors: Sosinsky Gina , Ellisman Mark
Published: July 2020

Approaches for exploration of biological structures with modern 3D microscopy techniques are expanding rapidly. These technological advances include not only the imaging of structures, but also the computational reconstruction methods for calculating three-dimensional structures. The computational techniques used to investigate the three-dimensional structure of macromolecular complexes, organelles or cells include crystallographic reconstruction, helical reconstruction, icosahedral reconstruction, single particle reconstruction, electron tomography and serial section reconstruction. These techniques have particularly useful in determining structures which are too small for light microscopy or too large for NMR or X-Ray structure determination or structures for which crystals are not available or order in the crystals is limited.

Advances in microscopes and associated computational capabilities have been substantial over the last few years. In this session, presentations will examine technical aspects and methods for three-dimensional reconstruction of biological structures from images acquired by electron microscopy and analyzed using the computational reconstruction techniques listed above.
Image Reconstruction from the Oversampled Diffraction Pattern
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Miao J , Chapman H , Sayre D
Published: July 2020

In recording the intensity of the diffraction pattern from an arbitrary object, the phase is lost. This gives rise to the “phase problem”in reconstructing the object in crystallography, where the pattern is sampled at the Bragg peaks. It was shown by Bates and by Hayes that sampling at twice crystallographic density (2x oversampling) in each dimension is sufficient in principle to obtain a full reconstruction of the object. It was pointed out by Sayre in 1991 that the diffraction pattern of a non-crystalline object is continuous, therefore the pattern may be sampled on a finer scale, providing the additional information for the image reconstruction.

The loss of phase corresponds to a loss of half the information. It seems therefore that 2x oversampling in each dimension (8x in three dimension) may be unnecessary. We find that oversampling 1.67x in each dimension is sufficient to obtain a reconstruction, even in the presence of noise. However our algorithm fails when we reduce the oversampling factor to 1.58x.
TEMTUTOR - a Teaching Multimedia Program for TEM
Authors: Kuokkala V-T , Lepistö TK
Published: July 2020

Teaching of transmission electron microscopy usually includes both lectures on the contrast theories, electron diffraction, etc., and practical hands-on operation of the microscope. The number of students attending the lectures is normally unlimited, but at the microscope, only a few persons can work at the same time. Since the microscopes are expensive, it would be of a great help if cheaper 'training' microscopes with basic imaging and diffraction capabilities were available. These functions, in fact, can quite easily be realized with fast personal computers and work stations, where the simulation of transmission electron micrographs and related diffraction patterns can help the student better understand the image formation processes. Adding text, audio and video help capabilities to the program, it can be made an efficient supplemental teaching tool.

TemTutor for Windows is based on microScope for Windows, which is a BF/DF TEM micrograph simulation program for dislocations and stacking faults.
Towards Sub-À Resolution Through Incoherent Imaging
Authors: Pennycook SJ , Chisholm MF , Nellist PD
Published: July 2020

As first pointed out by Lord Rayleigh a century ago, incoherent imaging offers a substantial resolution enhancement compared to coherent imaging, together with freedom from phase contrast interference effects and contrast oscillations. In the STEM configuration, with a high angle annular detector to provide the transverse incoherence, the image also shows strong Z-contrast, sufficient in the case of a 300 kV STEM to image single Pt and Rh atoms on a γ-alumina support. The annular detector provides incoherence by virtue of its large central hole, which is equivalent by Babinet's principle of complementarity to a bright field detector of the same size. For weakly scattering specimens, it shows greater contrast than the incoherent bright field image, and also facilitates EELS analysis at atomic resolution, using the Z-contrast image to locate the probe with sub-À precision. The inner radius of the annular detector can be chosen to reduce the transverse coherence length to well below the spacings needed to resolve the object, a significant advantage compared to light microscopy.
The Resolution of the SEM
Authors: Joy David C
Published: July 2020

The resolution of any microscope is usually taken as the benchmark of its quality. When thinking about the scanning electron microscope(SEM) a comparison of its resolution to the resolutions quot-ed for other comparable instruments such as the transmission EM or the scanning tunneling micro-scope has unfortunately led some users to the view that the SEM is only a second best choice. In fact the spatial resolution that can be anticipated for an optimized SEM is highly competitive with its peers making it clearly the microscopy of choice.

The resolution of the SEM depends on two classes of factors; those which are inherent to the use of electrons as an imaging tool, and those which relate to the performance of the instrumentation (and possibly of the operator) used to perform the microscopy. The use of electrons as the scanning probe, and the choice of secondary electrons as the usual imaging mode, potentially affects the achievable resolution in three ways.
Spatial Resolution in the Atom Probe Field Ion Microscope
Authors: Miller M K
Published: July 2020

The atom probe field ion microscope can resolve and identify individual atoms. This ability is demonstrated in a pair of field ion micrographs of an Ni3Al specimen, Fig. 1, in which the individual atoms on the close packed (111) plane are clearly resolved. Comparison of these two micrographs reveals that an individual atom was field evaporated between the micrographs. Due to the hemispherical nature of the specimen, the ability to resolve this two dimensional atomic arrangement is only possible on low index plane facets. The spatial resolution in field ion images is determined by a number of factors including specimen temperature, material, microstructural features, specimen geometry, and crystallographic location.

The spatial resolution of the data obtained in atom probe and 3 dimensional atom probe compositional analyses can be evaluated with the use of field evaporation or field desorption images. The field evaporation images are formed from the surface atoms with the use of a single atom sensitive detector whereas the field ion image is formed from the projection of a continuous supply of ionized image gas atoms.
Biological Applications of Environmental Scanning Electron Microscopy
Authors: C. J. Gilpin
Published: July 2020

Over recent years there has been relatively little experimental data produced by environmental scanning electron microscopy on biological applications. The author’s laboratory is situated in a multi-user facility based in a School of Biological Sciences and has examined a wide variety of samples over a 5 year period. The purpose of this paper is to present a number of biological applications, one in detail, in an attempt to illustrate the potential and pitfalls of the instrumentation.

A study has been made of the elastic bands used in dental orthodontics as a method of moving teeth. It is common clinical practice to replace the elastic bands at 24 hour intervals as it is known that the bands lose their elasticity and thus effectiveness during this period. The present study has examined the structure of such bands at time intervals after stretching to clinically used extension on a former and immersing the bands in water.
An SEM on a Chip
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Crewe DA , Feinerman AD
Published: July 2020

A silicon microfabrication technique has been applied toward the development of a Miniature Scanning Electron Microscope (MSEM). The fabrication technology is not only precise but is inexpensive compared to conventional methods of electron microscope construction and is easily extended to the construction of arrays of MSEMs for applications in high throughput e-beam lithography and wafer inspection.

An electrostatic electron lens consists of a series of planar electrodes with central apertures that are precisely aligned to and electrically isolated from one another. This structure is fabricated using silicon as the electrode material and Pyrex optical fibers as the insulators. The electrodes are fabricated on four inch (100) orientation silicon wafers that are patterned on both sides and anisotropically etched to form four orthogonal v-grooves and an open diaphragm with a circular aperture in the center. The apertures are formed by reactive ion etching. The wafers are then diced to create approximately 100 7 mm by 9 mm electrodes.
Surface Sensitivity and Resolution in LVSEM Imaging and Microanalysis
Authors: Boyes Ed
Published: July 2020

The surface sensitivity of both imaging and EDX chemical microanalysis of materials, micro-fabrications and nanostructures can be greatly enhanced by using low beam energies in the SEM (LVSEM). This has become more apparent with the advent of instruments which are relatively uncompromised in performance (<5nm) at a range of low voltages around 1kV, and especially ones with higher resolution (≤2.5nm) and full digital imaging to make a wide range of conditions more readily accessible (1). They yield images of natural surfaces retaining their inherent chemical and electronic image contrasts and with probe sizes comparable to those which we are familar with at high voltages, but where many samples require to be coated with metal. The traditional SEM resolution test samples for evaluating SEM imaging are far from a typical bulk SEM sample. The small heavy metal particles on a carbon support behave more like the STEM situation since the backscattering of electrons from the support, and hence the generation of type 2 secondary electrons, is very limited.
Sampling Depth Controlled by Accelerating Voltage in a Low Voltage SEM
Authors: Yao N , Harrison C , H. Adamson D , Park M , Chaikin P , Register R A
Published: July 2020

A fundamental new pathway to a basic understanding of nanostructured composite thin films has been recently afforded by advances in both high brightness field emission electron source and electron optics in the SEM. The key advantages of controlling the incident electron beam at low energies (< 5 keV) for surface imaging has been largely focused on goals such as the reduction of sample charging and minimization of macroscopic radiation damage. In this paper, we present a new opportunity to obtain sampling depth information by controlling the incident electron beam energy. One of the major factors which determines the contrast seen in SEM images is the interaction of the incident electron beam with the solid. As a result of this interaction, the secondary electron yield is proportional to the stopping power of the electron as described by the Bethe penetration depth,where dE/dl is the stopping power of incident electron with energy Einc and Emin is some suitable lower energy limit for the interaction.
Quantitative Analysis and Interpretation of Atomic Force Microscopy (AFM) Phase Imaging
Authors: Leonard DN , Batchelor AD , Russell PE
Published: July 2020

Gaps in the understanding and interpretation of data collected in various SPM modes are a direct result of the rapidly advancing scanning probe microscopy (SPM) technology. This systematic study is coupling classical metallurgical samples with a new surface variation mapping technique in an effort to further the quantitative comprehension of atomic force microscopy (AFM) phase imaging.

Phase imaging is a technique that has exhibited the ability to provide the microscopist with qualitative information of a material’s microstructure on the nanometer scale. Regions of a microstructure that exhibit incongruous mechanical properties like: friction, elastic modulus, composition, and viscoelasticity are displayed, in the resulting image, as regions of differing contrast. An example of this type of phase contrast is clearly seen in FIG. 1. A quantification of the phase shift will give new insight into the cause of the contrast mechanism, and reason for contrast reversal.
Recent Advances In Magnetic Force Microscopy: Imaging In The Presence Of External Fields
Authors: Gomez Romel D
Published: July 2020

In the last decade since its development, magnetic force microscopy[l] has emerged as a workhorse in imaging magnetic structures at the sub-micron length scales. It possesses the desirable attributes of robustness, straightforward implementation and a fairly well characterized image contrast formation. In recent years, we have successfully implemented MFM in the presence of a highly controlled external magnetic field.[2] Using this technique, it is possible to follow the sample’s magnetic evolution at various points along it’s magnetization curve. Further, by using standard software implementation, the images can be presented as an animation of the micromagnetic process. We applied this technique to study a variety of slow varying dynamics of magnetic systems, including the dc erasure of thin film recording media[3], the mechanisms of moment rotation and reversal, and the domain wall motion nanostructured magnetic elements[4,5].

In this talk, I will review the rudiments of the technique and show the “dynamics” of the magnetization of cobalt and Permalloy alloys interacting with external fields.
Phase Contrast Of Magnetic Cobalt Spheres
Authors: Graef M De , Nuhfer NT , McCartney MR
Published: July 2020

The recent increased interest in Lorentz Microscopy methods is due to two important factors: (1) the advent of digital detection systems (CCD cameras) and advanced computer controlled transmission electron microscopes, and (2) the continually decreasing length scale of magnetic recording media and related magnetic materials. Along with the increased experimental resolution and detection sensitivity one should ask the question: how small a magnetic moment can one detect with conventional Lorentz or electron holography techniques? And, perhaps more importantly, which technique should one use to obtain the best spatial resolution? To address these questions we identified a simple model system :the uniformly magnetized sphere.

The phase of the electron wave after passing through a region with a non-zero magnetic vector potential and an internal electrostatic potential Vscan be computed from the Aharonov-Bohm trajectory integral. For a spherical particle with a uniform magnetization and a constant mean inner potential (see geometry in Fig. la), this phase shift can be analytically computed.
Magnetic Force Microscopy Of Shape Memory Alloys: Identifying Two Magnetic Patterns
Authors: Neves BRA , Andrade MS
Published: July 2020

In this work, we report on the observation of two coexisting patterns in Magnetic Force Microscopy (MFM) images of shape memory alloys. The MFM signal of both patterns presents similar behavior with tip-surface separation. An investigation on the origin of these patterns presents strong evidence that both are of magnetic nature only and, furthermore, can be assigned as bulk and surface-related, respectively.

Shape memory alloys are a class of materials that exhibit martensitic transformation [1]. The shape memory effect, which may be defined as the property of recovering its original shape during a thermal cycle after a material has been apparently deformed in a permanent way, is found in several materials, including the Fe-Mn-Cr-Ni-Si alloy, studied in this work [1]. A standard metalographic process was employed to reveal ferritic-phase islands surrounded by the austenitic-phase matrix, which constitute the structure of this alloy. The images were acquired with a MultiMode microscope from Digital Instruments.
Magnetic Field Calibration Of The Jeol 3000 Feg Electron Microscope: Application To Studies Of Hard Magnets
Authors: Volkov VV , Crew DC , Zhu Y , Lewis LH
Published: July 2020

For quantitative magnetic image analysis it is important that the value of the magnetic field applied to the sample is known. Calibration of the magnetic field inside an electron microscope is not a simple procedure, however, because it requires the use of a special sample holder which contains a Hall probe sensor. We report here on a simple and effective procedure for calibration of the magnetic field at the sample position of the JEOL 3000 FEG transmission electron microscope (equipped with ultra-high resolution pole pieces URP-32F, point resolution of 1.6 Å and tilt angle ±30°) without the use of a special sample holder. The technique is based upon the fact that the magnetic flux present in a magnetized material in a field-free environment, known as the remanence Br, is a sensitive function of the largest applied magnetic field. The inverse of this principle — that the value of an applied field may be determined from measurements of the remanence, — was used to quantify the magnitude of the field present at the sample position.
Infrared Microscopy As A Failure Analysis Tool In The Thermal Inkjet Cartridge Industry
Authors: Tungol Mary Widmark
Published: July 2020

Four major components comprise an inkjet cartridge (Fig.lA): (1) the pen body which contains the ink and positions the cartridge in the printer; (2) an ink delivery system which supplies ink at the correct backpressure and flow rate; (3) a flex circuit which provides the electrical interconnect to the printer; and (4) the printhead which generates and directs the drops. Because of its complexity and small critical dimensions, the printhead poses the greatest analytical challenge for many failure analysis problems. Each printhead may contain as many as 300 firing chambers (Fig. IB). Each chamber consists of a resistor surrounded by a polymer-based barrier material which forms a cavity into which ink flows from the ink delivery system. The chamber is capped by a metal or polymer orifice-containing plate. Printing occurs when the resistor is heated to form an ink vapor bubble which subsequently ejects a droplet of ink though the orifice onto the paper.
In Situ Identification Of Automotive Paint Organic Pigments Using Infrared Microspectroscopy And Spectral Subtractions
Authors: Suzuki Edward M
Published: July 2020

A forensic examination of automobile paint may involve either a comparative analysis of two paint samples or an attempt to identify a recovered paint chip to determine the make, model, and year of the vehicle from which it originated. Along with microscopy, the main tool which most U.S. forensic laboratories use for such analyses is infrared spectroscopy. Paint binders are normally identified by this means together with some inorganic pigments. Until recently, however, there were no published reports describing the identification of organic pigments in the cured paint samples normally analyzed in the forensic laboratory. The main reasons for this stem from the difficulties in isolating these pigments from the inert paint matrices and the insolubilities of the pigments. Using infrared microspectroscopy and spectral subtractions, several organic pigments used in automotive finishes have now been identified in situ based on spectra of intact paint samples.

Infrared spectra were obtained of U.S. automobile original (OEM) finiśhes from the Reference Collection of Automotive Paints.
Characterization By Scanning Electron Microscopy (Sem) And Energy Dispersive X-Ray Spectroscopy (Eds) Of Solid Solution Single Crystals Grown On Earth And In Microgravity
Authors: Cochrane J C , Carpenter P K , Gillies D C
Published: July 2020

The II-VI semiconductor mercury cadmium telluride, composed of 80 mole percent HgTe and 20 mole percent CdTe, has been grown on Earth and aboard two NASA Space Shuttle flights in order to study the solidification of a solid solution semiconductor having a wide separation between liquidus and solidus. Segregation during solidification, high volatility of mercury, and strain fields associated with large temperature gradients make the growth of homogeneous, high-quality, bulk crystals extremely difficult. The traditional growth methods yield crystals with axial and radial compositional variations and secondary precipitates of tellurium, probably caused by gravityinduced, thermosolutally-driven flows just ahead of the growth interface. The purpose of growing these crystals in microgravity is to reduce gravity-induced convection. This should be advantageous for minimizing the density of crystal defects while also minimizing compositional variation transverse to the crystal growth direction.

The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces and NASA’s Advanced Automated Directional Solidification Furnace (AADSF).
Effect Of The Substrate Surface Termination On The Structure Of The Bi4Ti3O12 / SrTiO3 Interface
Authors: Jiang J C , Tian W , Theis C D , Schlom D G , Pan X Q
Published: July 2020

Bismuth titanate (Bi4Ti3O12) belongs to a family of layered perovskites (Aurivillius phases) that are important for nonvolatile ferroelectric memory applications. Recently epitaxial (001) Bi4Ti3O12 thin films have been grown on (001) SrTiO3 by reactive molecular beam epitaxy (MBE) in an adsorptioncontrolled growth regime. Bi4Ti3O12 has a monoclinic layered perovskite structure at room temperature which consists of alternating Bi2O2 and Bi4Ti3O10 perovskite layers (see the upper part of Fig. 1(b)). Due to the significant difference in crystal structure between film and substrate, the surface termination of the SrTiO3 substrate and the way in which growth is initiated might be expected to have a significant influence on the interfacial structure. In this work, we present high-resolution transmission electron microscope (HRTEM) studies of the Bi4Ti3O12 / SrTiO3 interfacial structure for Bi4Ti3O12 films grown on SrTiO3 substrates terminated with either the TiO2- or SrO-layers.

Bi4Ti3O12 thin films were grown on SrO- or TiO2-layer terminated homoepitaxial SrTiO3 buffer layers grown on SrTiO3 (001) substrates by reactive MBE.
Atomic Scale Characterization Of Interfaces And Defects In Non-Stoichiometricmulticomponent Oxides
Authors: Stemmer S , Streiffer S K , Sane A , Mazanec T J , Browning N D
Published: July 2020

The ability to obtain chemical information with (near) atomic resolution has recently become possible by a combined approach of Z-contrast imaging with electron energy-loss spectroscopy (EELS) in scanning transmission electron microscopes. This method is particularly interesting for the characterization of structure-property relationships in novel multicomponent oxides, which possess added functionality due to their high nonstoichiometry.

In this paper we demonstrate the capabilities of this method in analyzing the microstructural mechanisms of accommodation of non-stoichiometry, using two example systems: (Ba,Sr)TiO3thin films for DRAM applications, grown by MOCVD with different amounts of excess titanium, and an oxygen-deficient perovskite ceramic, SrCoOx. The experiments were performed in a JEOL JEM 201 OF field emission transmission electron microscope, operating at 200 kV, equipped with an annular dark-field detector, scanning unit and a post-column imaging filter (Gatan GIF 200). This microscope has been demonstrated to achieve probe sizes of under 1.5 Å.
A Stem Study Of A Germanium Island-Silicon Interface
Authors: Vanfleet RR , Basile DP , Kamins TI , Silcox J , Stanley Williams R
Published: July 2020

Growth of germanium or silicon-germanium on silicon 100 surfaces produces pyramid shaped islands after several monolayers of coverage. With further deposition, these islands will continue to grow until they reach a critical volume where a transition to a dome shape occurs. The critical surface coverage for island formation and the critical volume for the pyramid to dome transition depend upon the silicon to germanium ratio or degree of mismatch between the deposited material and the silicon substrate. Strain plays a dominant role in the shape transitions. Annealing studies have shown that the pyramid to dome transition.is reversible and is likely due to strain reduction related to interdiffusion. Annealing results in island growth, a decrease in the number of islands, and interdiffusion of the silicon and germanium. The interdiffusion relieves the strain and shifts the critical volume to a value exceeding the current volume of the dome shaped island thereby driving the transition back to pyramidal shape.
Microstructure Of Tin Ohmic Contacts On N-Gan
Authors: Liu R-J , R. W.Carpenter  , Kim M J
Published: July 2020

GaN is a direct, wide band -gap semiconductor (Eg =3.4 eV) which has a potential application in electronic and optical devices including UV-emitting lasers and bright p-n junction GaN light emitting diodes. In order to attain optimum device performance, it is necessary to develop lowresistance, thermally stable and uniform ohmic contacts.

In this study, the TiN/GaN contact synthesis and examination of contact performance were conducted at North Carolina State University. Si-doped n-GaN films were grown on 6H-SiC substrates via MOVPE with an A1N buffer layer. The TiN films were deposited in an ion-beam assisted, UHV electron-beam evaporation system. TiN growth was performed at a substrate temperature of 350 °C and a nitrogen pressure of about 2×10-4 torr. The deposition rate was 1- 1.5 nm/min. The TiN contacts deposited on (0001) n-GaN were ohmic with high resistivity in the as-deposited condition, but the resistivity decreased sharply in response to annealing. The TiN/GaN interface was examined by transmission electron microscopy to provide correlations between changes in microstructure and electrical behavior.
In Situ Uhv-Tem Oxidation And Reduction Of Metals
Authors: Yang J C , Yeadon M , Kolasa B , Gibson J M
Published: July 2020

In this proceedings, we present a review of our experimental results of our investigations of the mechanisms of the initial stages of copper oxidation. We examined the initial stages of Cu(001) oxidation and reduction by in situ ultra-high vacuum (UHV) transmission, electron microscopy (TEM). We observed surface reconstruction and nucleation and growth of copper oxide islands. We have examined the oxidation processes from oxygen partial pressures of 10-5 torr to atmospheric pressures and temperatures from 25°C to 600°C, in order to gain fundamental insights into this important gas-metal reaction.

Fundamental knowledge of gas-metal reactions, in particular oxidation, is important for a wide variety of materials science fields, such as dry corrosion, catalysis, as well as some thin film growth, such as ferroelectrics. However, there is a wide gap between information provided by surface science methods and that provided by bulk oxidation studies. The former have mostly examined the adsorption of up to ˜1ML of oxygen on the metal surface.
Quantification Of Segregation Levels Using Xeds In The Stem
Authors: Keast V J , Williams D B
Published: July 2020

The quantification of grain boundary segregation levels, as measured with X-ray energy dispersive spectroscopy (XEDS) in a scanning transmission electron microscope (STEM), is dependent on the size and shape of the interaction volume. The segregation level T (in atoms/nm2) is related to the intensities of the characteristic peaks in the X-ray spectrum, Is and Im, by

where ρ is the density of the matrix in atoms/nm3, Am and As are the atomic masses of the matrix and segregant respectively and ksm is the usual k-factor. The geometric factor, V/A, is the ratio of the volume of interaction to the area of the grain boundary inside in the interaction volume. Different models have been used to describe the interaction volume and these are illustrated in Fig. 1 and the appropriate expression for V/A is given in each case. In the simplest case, beam broadening is neglected and the interaction volume can be described as a cylinder with diameter equal to the probe size, d.