bluuebunny/crossref_metadata_2025 huggingface dataset:
The Disputed Discovery Of Element 43: A Reexamination Of An Elegant Early Use Of Wavelength-Dispersive X-Ray Microanalysis
Authors: Armstrong John T , Van Assche P H M
Published: July 2020

Typical modern histories of the discovery of the chemical elements report that element 43 was discovered in Italy in 1937 by Perrier and Segre. According to these accounts, the discovery was made by chemical separation in a sample of deuteron-bombarded molybdenum, supplied by E. Lawrence, and thus represent the first discovery of an element produced artificially and is the reason for the name “technetium” (Tc) chosen by the investigators. Some accounts might note in passing that the existence of element 43 was predicted in the early part of the 20th century on the basis of the periodic table, and that the element was reported as discovered in natural samples by x-ray emission spectroscopy in 1925 and called “masurium” (Ma). These reports, however, invariably call this discovery erroneous and sometimes refer to the investigators (typically left unnamed) as “deluded”.

The original reported discovery of “masurium” was made in an exhaustive investigation of some thousand mineral separates of Nb-Mo-U-rich phases involving early elegant use of wavelengthdispersive x-ray microanalysis.
Precision In X-Ray Data Computed By Monte Carlo Calculations
Authors: Lifshin Eric , Linsebigler Amy , Gauvin Raynald
Published: July 2020

The analytical expressions used in ZAF and ϕ(ρz) calculations give single values for the composition of each element for a single set of intensity measurements from samples and standards. Confidence intervals in composition are established by looking at the variability of repeated measurements. They are usually attributed to x-ray counting statistics or experimental reproducibility factors such as sample repositioning. Uncertainty in the equations themselves or the parameters that go into them are rarely considered. The derivations of ZAF and ϕ(ρz) equations are primarily based on the case where flat single-phase regions, relative to the x-ray excitation volume, are examined using normal electron beam incidence. Use of these equations has been extended to non-normal electron beam incidence as well as the quantitative analysis of layered structures, but usually with less theoretical justification. Finally, special experimental cases including porous structures, rough surfaces, vertical interfaces and small particles are very difficult or impossible to model by the single application of a set of analytical equations to convert measured x-ray intensities to elemental composition.
Compound Standards For Light Element Eds In Aem, Sem And Lvsem
Authors: Boyes E D
Published: July 2020

For a number of years we have used in our laboratory a simple extension to light elements of the classical ClifF-Lorimer approach using stoichiometric compound standards containing pairs of heavier elements to determine independently the EDS detector sensitivity contribution to quantitative analysis in the AEM. It is now also extended to direct light element LVEDS analysis in the SEM at low voltage (<5kV). This approach may be more practical, accessible and easily reproducible for routine use than the elegant custom thin film fabrications reported by Egerton, but the latter method has other substantial advantages, including well defined thicknesses, in the most sophisticated applications. As the types of advanced materials have expanded to include ceramics and polymers the requirements for analysis have also changed. In many cases the light elements are now the majority species in advanced materials and the corrections based on older standards are huge; and therefore inevitably rather limited in accuracy.
The Origin Of Electrical Activity At Grain Boundaries In Perovskites
Authors: Kim Miyoung , Browning N D , Pennycook S J , Sohlberg K , Pantelides S T
Published: July 2020

The electrical activity of grain boundaries in perovskites, of which SrTiO3 is a model system, is the basis for their use as capacitors, varistors and positive-temperature coefficient resistors. In related materials this same electrical activity is often detrimental. The outstanding example of a negative effect is the reduction in critical current by several orders of magnitude across grain boundaries in YBa2CU3O7-δ as the boundary misorientation is increased from 0°-45°. Grain boundaries are also likely to profoundly affect properties such as domain wall motion in ferroelectric and magnetic perovskites. The origin of the electrical activity is ubiquitously attributed to the existence of grain boundary donors, usually assumed to be impurities, which set up a double Schottky barrier as they are screened by dopants in the adjacent bulk crystal. We show here, that although electrical barriers can doubtless be modified by dopants, the grain boundary structure itself is the intrinsic origin of the socalled grain boundary donors.
Segregation In Cocrptta/Cr Magnetic Recording Media Measured By Eftem
Authors: Bentley J , Wittig JE , Nolan TP
Published: July 2020

Development of high-density longitudinal magnetic recording media (used for computer hard disks) with good noise performance and high thermal stability requires optimization of both alloy composition and processing methods. In CoCr(PtTa) thin films, intergranular Cr segregation is responsible for decoupling the magnetic exchange between the small ferromagnetic grains. The corresponding Cr depletion within the grains affects the “bulk” magnetic anisotropy. However, the nanoscale structural and chemical details that are needed for modeling and for guiding material development are not well understood. Energy-filtered transmission electron microscopy (EFTEM) has been used to characterize a series of CoCrTa/Cr, CoCrPt/Cr, and CoCrPtTa/Cr media sputtered under various processing conditions, in order to understand their structure-property-processing relationships.

Processing typical for hard-disk media was used: 30 or 60-nm films of a Cr underlayer followed by a Co alloy were d.c. magnetron sputtered onto a NiP-plated Al substrate pre-heated to 250°C.
Exelfs As A Tool For Investigating The Local Structure Of Bulk Glass-Forming Metal Alloys
Authors: Alamgir F, M , Ito Y , Williams D B , Jain H
Published: July 2020

The discovery of amorphous, or glassy, metallic alloys in 1959 posed an intellectual challenge. How can one describe the structure of glasses when there is no long-range periodicity? What can the structure tell us about why certain metal alloys form glasses more easily than others? First, some universal characteristics, if any exist, of the structure metallic glasses needed to be found. A convincing model was proposed for the structure of metallic glasses based on Bernal’s dense random packing (DRP) structure. Central to this proposal is the idea that the structure of metallic glasses is that of the random filling of space by non-interacting identical spheres. In this model, strongly directional interatomic bonds do not play an important role in determining the structure of metallic glasses. This model is hpwever in conflict with one proposed by Chen, which correlates increased glass formability with increased chemical interaction between dissimilar atoms.
Atom Probe Field Ion Microscopy Of Multilayer Thin Films
Authors: Larson D J , Petford-Long A K , Cerezo A , Anthony T C , Miller M K
Published: July 2020

Multilayer film (MLF) structures which exhibit giant-magnetoresistance (GMR) properties have applications in the areas of magnetic recording and computer memory. The magnetic properties of MLF structures are dependent upon structural and compositional variations at the atomic level. Thus, structural characterization with high spatial resolution, especially at layer interfaces, is important in order to optimize device performance with respect to processing and operating conditions. Atom probe field ion microscopy (APFIM) is one technique that has the capability to characterize the local structure and composition of MLF devices with sufficiently high resolution. However, a major difficulty has been successful specimen preparation from MLF materials, which requires fabrication of a sharply pointed needle (radius <50 nm) containing the layers of interest in the apex region. Research on specialized field ion specimen preparation techniques which use focused ion beam milling has recently enabled nanoscale MLF structures to be investigated. In the present paper, the application of atom probe microanalysis to two different MLF structures is presented.
Complex Layer Stacking In Muscovite: A Hrtem Study
Authors: Ma Chi , Rossman George R
Published: July 2020

One-, two- and three-layer polytypes are common in muscovite (sheet silicate). Based on high-resolution transmission electron microscopy (HRTEM) and analytical electron microscopy (AEM) examinations, we report in the discovery of complex 5-layer and 7- layer polytypes in natural muscovite for the first time (Fig. 1) and the implications of polytype transitions.

Three main structures are found in muscovite crystals in a sample from Oreana, Nevada, which are 1M, 2M1, and a disordered structure often containing short-range ordered stacking sequences. On the scale of a few micrometers, muscovite occurs as ordered crystals, disordered crystals, and crystals with regions of ordered and disordered layer stacking.

Short-range ordered 5- or 7-layer repeats are found in some disordered structures where single 4-, 6-, 9- or 10-layer intergrowths occur occasionally with 2- and 3-layer repeats. Such complex polytypes have not been observed before in either natural or synthetic muscovite, although 5- and 7-layer structures are commonly present in trioctahedral micas (i.e., biotite) (Baronnet, 1992).
Boundary Analysis Of SrTio3 Ceramic Condenser
Authors: Kawasaki Masahiro , Yoshioka Tadanori , Sato Shigeki , Watanabe Kazuto , Shiojiri Makoto
Published: July 2020

SrTiO3-based semiconducting ceramics are widely used to electric devices such as dielectric condensers and varistors due to their properties of high dielectric constant, high dispersion frequency and small temperature dependence of the dielectric constant. The electric properties of these ceramic devices have been studied and found to be deeply influenced by the crystal growth mechanism, the grain boundary layer characteristics and the sintering atmosphere that is represented by such factors as oxygen partial pressure and processing temperature which relate to the atom vacancy formation. Atom vacancies, which play an important role to the electrical properties, have been detected by cathodoluminescence (CL) spectroscopy with scanning electron microscopy (SEM).

A ceramic condenser (Sr0.94Ca0.05Ba0.01)0.99TiO3 was investigated by Hitomi el at: using transmission electron microscopy (TEM). The material is a boundary layer (BL) semiconducting ceramic condenser, having dielectric layers between semiconducting grains. The same condenser material was investigated in this report at the grain boundary region using high resolution (scanning) transmission electron microscope (TEMSTEM) capable of High Angle Annular Dark Field (HAADF) technique.
Microstructural Characterization Of The Pd-Ge Ohmic Contact On Gaas By Cross-Sectional Transmission Electron Microscopy (Tem)
Authors: Radulescu F , McCarthy JM
Published: July 2020

In the last decade, Pd-Ge contact system emerged as the most promising replacement of the Au-Ni-Ge alloy, still used by most of today's GaAs technology. Its better electrical properties stem from the fact that contact formation is based on a series of solid state reactions without any melting of the metal thin films and the GaAs substrate taking place during annealing. Research studies by E.D. Marshall et al. (1) demonstrated that thermally stable contacts with low resistivities could be achieved by low temperature annealing of Pd and Ge thin films. Their studies also revealed that the excess Ge is regrown on top of the GaAs substrate by a solid state epitaxy mechanism.

Typical TEM cross-sectional specimen preparation techniques limit the electron transparent area and make the global characterization of the contact difficult. In this study, we employed a focus ion beam (FEB) method as described by Bassile et al.(2), which allowed us to observe a minimum of 4 microns of the interface cross section in each of the specimens examined.
Measurement Of Interfacial Segregation In Aluminum-Magnesium Alloys Using A Feg-Tem And Eds
Authors: Vetrano JS , Henager CH
Published: July 2020

Aluminum-magnesium alloys are currently being utilized in lightweight automotive components and their good strength and weldability characteristics has made them candidates for increased use. The primary problem with using aluminum alloys for automotive applications is their relatively low formability. Superplastic forming (SPF) is a viable method for producing high elongations and is enabled in these alloys by the manipulation of intermetallic particles (e.g. Al3Sc) that restrict grain growth at the high homologous temperatures necessary for this technique [1]. SPF of Al-Mg-Mn-Sc alloy has yielded elongations of over 600% [2]. However, Al3Sc particles age rapidly at high temperatures which can reduce their strengthening characteristics following deformation. It has been experimentally observed that the addition of Zr to Al-Sc alloys retards the aging of the Al3Sc precipitates [3]. This is beneficial for high temperature conditions like superplastic forming and welding. In this study we examine the location of Zr in the strupturc and how it may be inhibiting particle aging.
A Tem Investigation Of Nanoparticle Contact
Authors: Yao Y , Thölén AR
Published: July 2020

A comprehensive understanding of the relation between structure and properties in nano-materials calls for an extensive knowledge of the adhesion between nanoparticles. Electron diffraction contrast from the stress field caused by adhesion between contacting particles yields a detailed information on surface energy, grain boundary energy, dislocation and interphase formation mechanisms. However, the image interpretation is hindered by the scarcity of defined image condition data to fit the theoretical simulations due to the non-trivial TEM experimental situation on such a nanometric scale.

In our contribution, we challenge the above characterization complications by initiating CBED, HREM, and EELS on contacting nanoparticles with a CM200 FEG TEM. The main objective of our investigation is a quantitative simulation of the contacting stress field images from contacting nanoparticles and a quantitative characterization of the adhesion properties. In our approach, we started with cobalt particles which were coherently precipitated in a Cu-Co0.2wt% alloy, and then extracted using the carbon evaporation replica technique.
Interfacial And Surface Study Of Mo-Au And Al-Ag Bilayers For Si-Based Photodetectors
Authors: Li Mary J , Aslam S , Chen TC , Finkbeiner FM , He C , Kelley RL , Mott DB , Stahle CK , Stahle CM , Wang L
Published: July 2020

Bilayer thin films have been utilized in superconducting transition-edge sensors (TES) for photodetector development. A TES is formed with a normal metal conductor film and a superconductor film, so called bilayer, deposited on a subtract. In its,transition temperature region, the resistance of the superconductor film is extremely sensitive to the temperature. When an incident radiation ray arrives, the temperature of the bilayer increases, leading the resistance increases tremendously. A superconducting quantum interference device measures the current variation for read-out. By varying the relative thickness of the normal metal conductor layer and the superconductor layer, one can adjust the transition temperature of the bilayer to a desired range according to the proximity effect. TES bilayers are fabricated on Si-based substrates for the development of infrared, ultra-violet, and x-ray detectors.

Various normal and superconducting metal combinations are considered as bilayer candidates. When two metals are brought together, the concerns usually rise to those materials issues that may affect TES performance.
Al Compositional Profile In Algaas/Gaas Quantum Wells
Authors: Cai D Q , Zou J , Cockayne. D J H
Published: July 2020

The TEM thickness fringe method [1] was developed as a potential routine technique to determine compositional profiles in quantum well systems. This technique has the advantages that a) TEM sample preparation is simple and the experiment is easy to set up and b) thickness fringe profiles show fine structure which is sensitive to chemistry [2]. In this paper, we demonstrate the ability of the method to measure the chemical abruptness at the interface between two layers of different composition.

90° wedge AlGaAs/GaAs TEM samples were prepared by the cleavage method, where the samples were cleaved along two orthogonal {110} planes. The samples were mounted on Cu grids and were investigated in a Philips EM430 TEM. Samples were orientated to the [100] direction precisely and bright-field images were acquired digitally using a CCD camera. Fig 1 shows an enlarged image of thickness fringes.

Since the edges of samples are 90° wedges, the thickness at any point can be accurately determined and the fringe profile can be compared with fringe profiles calculated for a range of Al compositions.
Thermal Stability of The Copper/Tantalum Interfaces In Advanced Microelectronic Metallization
Authors: Kwon Kee-Won , Lee Hoo-Jeong , Sinclair Robert
Published: July 2020

In the copper metallization adopted for better speed and reliability in microelectronic devices, the choice of underlayer is one of the major concerns. Its requirements include low electrical resistance, adhesion to Cu and adjacent dielectric materials, confinement of Cu from drifting, and nucleation and texture enhancement of the overlying Cu film. Metallic tantalum is a very promising candidate. In this paper, the thermal stability of Cu/Ta interfaces is investigated to estimate the reliability of such a Ta underlayer.

Thin Cu and Ta films were consecutively deposited without breaking vacuum using a dc sputtering method to simulate the seed layer and underlayer in a Cu metallization structure. All the synthesized Ta films were the metastable tetragonal structure rather than the stable body-centered cubic (bcc) phase.

We have shown that (111) Cu grows epitaxially on top of (002) tetragonal Ta even though the Cu and Ta have hexagonal and tetragonal atomic arrangement on those planes, respectively. Using electron diffraction in cross-sectional and plan-view samples, an unexpected atomic matching at the interface was discovered as shown in Figure 1(b).
Structure Determination Of The Al2cumg Intermetallic Phase
Authors: Radmilovic V , Kilaas R , Dahmen U
Published: July 2020

The mechanical properties of Al-Cu-Mg alloys depend on a dispersion of Al2CuMg phase precipitates which form as laths along <100>A1, with {012}A1 as the habit plane. Despite extensive study, the crystal structure, morphology and interface structure between the Al2CuMg intermetallic phase and the Al matrix are still not well understood. Since the mechanical behavior of Al alloys strengthened by the S-phase cannot be controlled without a clear understanding of its crystallography and interface structure, the goal of this investigation was to characterize the crystal structure, evolution and interface structure of the S-phase using quantitative electron beam characterization techniques. Several models have been proposed for the crystal structure of Al2CuMg. A widely accepted model of the S-phase was given by Perlitz and Westgren (PW) [1], shown in Fig. 1. The unit cell of the PW model is orthorhombic with unit cell dimensions a = 0.4 nm, b = 0.923 nm, and c = 0.714 nm, space group Cmcm, containing 16 atoms in the ratio Al:Cu:Mg = 2:1:1.
Encapsulated Fullerenes Within Single Wall Carbon Nanotubes
Authors: Smith Brian W , Luzzi David E
Published: July 2020

It is well documented that the pulsed laser vaporization of graphite produces both carbon nanotubes and C60 in the presence of certain metallic catalysts. In nanotube production most of the Ceo is removed along with other residual contaminants during succeeding purification and annealing steps. The possibility of C60 becoming trapped inside a nanotube during this elaborate sequence has been considered but not previously detected.

Nanotubes are observed with high resolution transmission electron microscopy under conditions chosen to minimize both exposure time and irradiation damage. Since a nanotube satisfies the weak phase object approximation, its image is a projection of the specimen -potential in the direction of the electron beam. The image has maximum contrast where the beam encounters the most carbon atoms, which occurs where it is tangent to the tube’s walls. Thus, the image consists of two dark parallel lines whose separation is equal to the tube diameter, 1.4 nm.
Mesostructure Of Pd And Pt Nanoclusters Chemically Stabilized With Phosphide And Phenanthroline Ligands: Hrtem And Aem Characterization
Authors: Oleshko Vladimir P , Crozier Peter A , Schryvers Nick , Vargaftik Michail
Published: July 2020

The noble metal (Me = Au, Pd, Rh, and Pt) polynuclear coordination compounds of Chini’s type eventually serve as a remarkable bridge between molecular clusters and metal colloids. The sizes of the metal cores of the cluster compounds are close to lower sizes of colloidal metal particles. However, chemically stabilized nanoclusters have a distinct ligand environment with a definite stoichiometry inherent to molecular clusters. Interest in structures of the cluster compounds has increased in recent years in view of their unique selective catalytic properties under mild conditions, which, in principle, open a way to the development of a new branch of catalysis by metal clusters, quantum-size effects in the thermodynamic properties, and applications as nano-sized electronic devices (quantum dots). A key feature in structural characterization of such species (they are amorphous solids usually unsuitable for x-ray diffraction analysis) is to understand the relations between the atomic arrangement, electronic structure and chemical reactivity.
Morphological Variations Of Nano-Scale Powder And Deposits Of Ain Produced By Vapor Phase Synthesis
Authors: Di lello BC , Moura F J , Solόrzano I G
Published: July 2020

Aluminum Nitride (AIN) has arised as a promising synthetic material, valued for its high thermal conductivity coupled with high electrical resistivity. These properties, associated with the fact that AIN is nontoxic and has thermal expansion characteristics which closely match those of silicon, makes it an excellent material for electronic packaging. Currently two commercial processes are primaly used for the manufacture of AIN powder, the direct nitridation of the metal, and the carbothermic reduction of the alumina in the presence of nitrogem.

In this work, nanosized aluminum nitride particles were synthesized from the phase using ammonia and aluminum chloride vapor as reactants. This system consists of a vaporization system, ammonia (NH3) distributor, tubular synthesis reactor and powder collection system. The aluminum chloride (AlCl3) vapor starts to react with ammonia injected in the synthesis reactor inlet position (mixing zone). The aluminum nitride nucleates and grows along the reactor length. The aluminum nitride powder produced was collected and chemically and physically characterized.
Image Simulation of Solid Xe Layers at an Interface of a Liquid Xe Inclusion and an Al matrix
Authors: Fujii T , Dahmen U , Johnson E , Birtcher RC , Donnelly SE , Allen C W
Published: July 2020

Xe inclusions can be formed in an Al matrix by ion implantation. The inclusion size and state (solid, liquid or vapor) can be controlled by changing the total ion dose and implantation temperature. Inclusions below about 10nm in size have been reported to be solid with a face centered cubic structure and a lattice parameter of about 0.6nm. Small solid inclusions have cuboctahedral shapes bounded by {111} and to a lesser extent by {100} facet planes. Larger liquid inclusions maintain their facets on the {111} planes of Al but the {100} facets become rounded. It is found that high resolution images of these liquid Xe inclusions exhibit an unusual contrast effect similar to that previously observed for liquid Pb inclusions in Al. This contrast is limited to the {111} facets and could indicate the presence of a thin solid layer of Xe. In this work we investigate the origin of this contrast effect by HRTEM observation and image simulation.

Nanosized Xe precipitates were formed in an Al matrix by ion implantation with 35 keV Xe at 474K to a dose 5×1015 ions/cm2. Through focus series of high resolution electron micrographs in the <110> zone axis orientation were taken on the Berkeley ARM-1000 at an accelerating voltage of 800kV.
Image Simulation of Small Pt Particles and its Application to Lattice Spacing Measurements in Catalysts
Authors: Tsen S-C Y , Crazier P A , López Cartes C , Liu J , Calvino JJ
Published: July 2020

The technique of high resolution imaging is important for characterizing the structure of small metal particle catalysts and nanophase materials. For bimetallic systems, it is possible to use local lattice parameter measurements to identify alloy compositions in ensembles of nanometer sized metal particles [1]. However, determining alloy composition is challenging because changes in lattice parameters of only a few percent must be reliably detected. We have performed measurements of the apparent d(111) fringe spacing on both simulated and experimental HREM images from Pt particles in the size range 15 - 35 Å. A series of initial image simulations of Pt cubeoctahedrons with 17 Å (201 atoms) and 34 Å (1289 atoms) in diameter have been studied in order to understand the effect of different parameters on the accuracy of lattice spacing. The clusters were built using the Rhodius program developed by Botana et al [2]. Starting with a bulk crystal we create cubeoctahedra by applying successive cuts along either the (111) or (100) direction. A supercell size of 50Å was selected and the particles were oriented at or close to the [110]. Images were calculated by the multi-slice techniques using both the CERIUS and EMS applications. The supercell was divided into 20 slices and the following parameters were used in the calculation Eo = 400 kV, Cs = 1mm, Δf= -320 Å, focal spread = 80 Å, convergence = 0.5 mrad and atomic vibration = 0.35Å.
A UHV Diffraction Camera With Energy Filter for Convergent Beam RHEED and TED.
Authors: Weierstall U , Zuo JM , Kjørsvikf T , Spence JCH
Published: July 2020

A UHV diffraction camera has been built which can be used in either transmission or reflection mode. Fig. 1 shows a schematic view of the instrument. The optical axis of the instrument is vertical, with gun below and a downward-looking CCD camera on top. The pressure with gun operating is 1×10−10 Torr. An ion pump and oil-free turbo system is used. The electron gun is a fully bakeable custom UHV RHEED gun with LaB emitter and two magnetic lenses. This allows the beam to be focused to an area of about 1 micron on the surface of the sample. The gun works in the energy range of l-50keV. A double tilt stage, with sample exchange, has been built which allows azimuth rotation by 360° and tilt by ° 15°. The sample can be resistively heated on the stage up to 1300°C. The sample holder can also be used with 3mm diameter TEM grids for transmission diffraction. An external lens-coupled liquid-nitrogen cooled Princeton CCD camera with 1024×1024 pixels is used for image acquisition, viewing a transmission phosphor through a lead-glass window.

The energy filter consists of three spherical grids serving as a retarding field energy filter. The design is similar to that of Horio [1]. The first and last grids are grounded, while the center grid holds the retarding voltage. High voltage stability up to 10kV has been achieved with this filter. Fig. 2 shows an energy loss spectrum obtained.from the specular spot of the Si(111) surface. The spectrum was obtained from the measured integrated intensities by numerical differentiation.
CBED Investigations of Mesoscopic Semiconductor Structures
Authors: Lakner H , Schulze-Kraasch F , Mendorf C , Brockt G
Published: July 2020

Ternary and quaternary heterostructures from III-V-semiconductors get more and more importance in the fabrication of high-speed/high frequency devices in telecommunication systems. One of the key parameters for the performance of such devices is the crystalline quality and especially the amount of tetragonal distortion in strained layers on a nanometer scale. Strain can cause problems for the growth of such layers like relaxation induced defects, especially for the case of a high value of lattice mismatch. However, strain and the associated influence on the band structure can be used consciously for the design of tailor-made heterostructures (band gap engineering). Therefore, the spatially resolved investigation of local crystal properties (tetragonal distortion or strain and strain relaxation) is a key tool for the characterization of strained layers.

Convergent beam electron diffraction (CBED) patterns and convergent beam imaging (CBIM) can be used to evaluate informations on the local crystalline structure. E.g. the position of the High Order Laue Zone (HOLZ) lines in the CBED patterns is sensitive to the local strain and therefore can be used to determine strain and relaxation effects in heterostructures quantitatively. But in practice the applicability of CBED is often limited by a lack of ultimate spatial resolution and/or of sensitivity.
Investigation of Low Symmetry Crystals Using Elctron Backscatter Diffraction
Authors: Dingley DJ
Published: July 2020

Electron backscatter diffraction patterns obtained from low symmetry crystals can present difficulties for automated pattern recognition. For example, when only a single zone axis is observed in the diffraction pattern and the Kikuchi bands used for indexing all pass through the zone axis then only two-dimensional crystallographic information is obtained. This results in there being a 180 degree ambiguity in the measured orientation. Furthermore, it is often observed that in automated indexing of quartz, an additional ambiguity is introduced when the zone axis imaged is [0001]. In this case it is difficult to distinguish between the true orientation and it’s twin. This ambiguity is overcome only if Kikuchi bands from the upper Laue zones are used in the indexing. However, in automated indexing it is normal for the computer to select the strongest Kikuchi bands visible and these will not be those from the upper Laue zones when the [0001] zone axis is imaged. This and other pseudo symmetries have been observed and have been overcome by applying correction procedures during data collection and in post collection analysis.
Phase Identification of Individual Particles by Electron Backscatter Diffraction (EBSD)
Authors: Small J , Michael J
Published: July 2020

Backscattered electron Kikuchi patterns (BEKP) were first observed by Alam et al. in 1954. J.A. Venables and C.J. Harland made the initial observation of BEKP and in the scanning electron microscope in 1973. In 1996, Goehner and Michael developed an electron backscatter diffraction (EBSD) system that uses a 1024 × 1024 pixel CCD camera coupled to a thin scintillator rather than photographic film. In their system, the quality of the raw patterns is improved by the use of “flat fielding” which normalizes the raw image to a “flat field” reference image that contains the image artifacts, including background, but not the crystallographic information. Automated pattern analysis is carried out using a Hough transform to locate bands and band edges in the pattern. The resulting crystallographic information is coupled with the elemental information from energy or wavelength dispersive x-ray spectrometry and the phase is identified is made through a link to a database such as the Powder Diffraction Files published by ICDD. An indexed pattern of the suspected phase is then synthesized for comparison to the unknown. This system is marketed commercially by Noran Instruments and offers the first practical method for rapid identification of unknown crystallographic phases in the SEM.
EBSD With FEGSEM - Issues, Advances and Applications
Authors: Humphreys FJ , Brough I
Published: July 2020

A standard commercial EBSD system, comprising a CCD camera (Nordif) and acquisition software (HKL Technology) has been interfaced to a Philips XL30 FEGSEM, and the spatial and angular resolutions for EBSD compared with a conventional W-filament JEOL 6300 SEM equipped with a similar EBSD system.

In characterising a grain or subgrain structure, overlapping diffraction patterns are obtained at the boundaries, and the effective spatial resolution can be defined as the distance over which the patterns cannot be solved. The spatial resolution is best in the direction parallel to the specimen tilt axis (LA), typically some three times better than for the direction perpendicular to the axis. The resolution is conveniently determined by measuring the fraction of patterns which are solved (Ns) during a raster scan of the sample. For a microstructure of equiaxed grains of size D, LA is given approximately by D(1-Ns)/4. Figure 1 is a plot of Ns against D−1 for aluminium samples under optimum operating conditions, and it is seen that the spatial resolution in the FEGSEM is some three times better than in the W-filament SEM.

The effect of beam current on LA is shown in figure 2. For the W-filament SEM, LA is a strong function of the probe current.
Adaptive Orientation Imaging Microscopy
Authors: Yang W , Wu C-T , Adams BL , De Graef M
Published: July 2020

This paper describes a new form of orientation imaging microscopy: Adaptive Orientation Imaging Microscopy or AOIM. In standard OIM experiments the local orientation of the crystal lattice is determined with respect to a suitable reference frame by acquiring and indexing electron back-scattering (EBS) patterns on a square or hexagonal grid of sampling points. Since its invention, OIM has been extensively used to characterize polycrystalline materials. With the fast development of computers and CCD camera systems in the past few years, the standard OIM can now acquire and index of the order of 4000 EBS patterns per hour.

In a typical OIM experiment one is usually interested in either the overall texture of. the sample, or in the types and relative frequencies of grain boundaries. In the former case the proper way of acquiring orientation data involves the use of an equidistant grid of sampling points. In the latter case, however, a large fraction of the acquisition time is wasted sampling the grain interior, which does not provide any information about the grain boundaries.
Choosing an Electron Backscattering Pattern (EBSP) System.
Authors: Eades Alwyn
Published: July 2020

Recent advances in cameras and computers have made it possible to build electron backscattering pattern (EBSP) cameras which can give crystallographic information from diffraction patterns in the scanning electron microscope (SEM) on a routine basis.[1] There are a few hundred such systems world wide and the number is growing fast. In the case of crystalline samples (nearly all applications of SEM outside the biomedical field), it will surely soon be considered essential to fit an SEM with an EBSP system, just as it is now considered essential to have the SEM equipped with an energy-dispersive x-ray spectroscopy (EDS) system. There are at least four commercial manufacturers of EBSP systems. In the next few years, then, I anticipate that many owners of existing SEMs as well as buyers of new instruments will be faced with the problem of selecting an EBSP system. This paper presents some of the issues involved in making such a choice.

As in many technical decisions, different people will have different needs and put different priorities on the specifications to be met. An instrument which is to be used to do repeated analyses of aluminum for beer cans will have different needs from a system used mostly to teach crystallography, and those will be different in turn from the needs of a system used to determine which phases are present in geological samples.
Crystallographic Characterization of Sputter Deposited Nb-Cu Thin Films Using Electron Backscatter Diffracted Patterns.
Authors: Loloee R , Pratt WP , Crimp M A
Published: July 2020

Crystallographic structure plays an important role in determining the fundamental physical properties of metallic thin films and superlattices, and structural characterization of such films is crucial for furthering the application of these materials [1]. Epitaxial films are usually characterized using a wide range of techniques including x-ray diffraction, REED, neutron diffraction, and highresolution electron microscopy. A complementary approach is electron backscatter patterns (EBSP), which is an SEM technique that can be used to measure crystallographic orientations of single or polycrystals [2].

In this work, EBSPs have been used to characterize the crystallite size and orientation of sputterdeposited Cu films. The EBSPs were formed in a CamScan 44FE SEM and recorded using an ORTEX CCD camera system. The images were analyzed using the Channel+ software package, and orientation maps were plotted using Channel+Ice [3].
Comparison of Environmental Secondary Electron Detector
(ESD) Imaging and Electron Diffraction Mapping of a Nickel Tape Using the Environmental Scanning Electron Microscope (ESEM)
Authors: Goddard R E , Hascicek Y S
Published: July 2020

A relationship between the local microstructure (crystallographic orientation) of a sample and an image from a scanning electron microscope (SEM) has been an elusive goal. Being able to show the structure from an exact area and relate it to other data is essential to the understanding of the structure relationship to the entire sample. Conventionally microtextural information of tapes is obtained by using x-ray diffraction and pole figures. But this only provides information about the global texture. The precise location is not well defined. The ability to physically transfer the sample from the x-ray diffractometer to a SEM and accurately state that this is the same area has been impossible. Electron Backscatter Diffraction Patterns (EBSPs) have been obtained in an electron microscope and the exact area in relation to the rest of the sample is determined. Thus larger areas can be defined and put together to form a composite of an entire sample. This, however, may be hard to accomplish in that defined areas for the image scan may be at a different scale than the EBSP scan. A contrast method of imaging in the ESEM using an increased vacuum and the ESD yields a good correlation to mapped areas obtained from EBSPs or also known as backscatter electron Kikuchi diffraction patterns (BEKPs or BKPs).
Recent Advances in Gaseous Detection Modes in the ESEM
Authors: Hardt T A , Knowles W R
Published: July 2020

The Environmental Scanning Electron Microscope, or ESEM, is the only class of SEM that can image in a gaseous environment that will maintain a sample in a fully wet state. The use of the patented Gaseous Secondary Electron Detector, or GSED, which amplifies the secondary electron signal with the gas, has allowed the ESEM to image a multitude of samples with true secondary contrast. Recently, several new modes of imaging in a gas have been developed and will allow further expansion of the capabilities of the ESEM.

To maintain pressures in the ESEM up to 20 Torr (27 mbar), the use of multiple, differentially pumped apertures, is required. This can place a restriction on the low magnification range. In the large field detection mode, all magnification restrictions are removed. Magnifications as low as lOx may be achieved. This is similar to many conventional SEMs.
Spatial Correlation of Elemental Impurities and Charge Contrast Image Detail in Gibbsite
Authors: Baroni Travis C , Griffin Brendan J , Lincoln Frank J
Published: July 2020

Charge Contrast Imaging (CCI), is a recently reported technique allowing the imaging of the internal microstructure of non and poorly conductive materials. In previous work, the relationship between controlled growth events in batch-precipitated gibbsite, Al(OH)3 and the appearance of contrasting bands in CCIs has been empirically correlated. The data presented was spatial, based on the number and dimensions of growth rings, however no interpretation of the contrast variation was made. Suggestions that the contrast may be related to charge trapping, which in turn is related to conductivity pathways and impurity concentrations indicates that the technique may provide insight into crystallisation processes. The current work examines the spatial distribution of impurity elements and their effect on the contrast observed within growth layers in charge contrast images of gibbsite.

Analyses for Ca, Fe and Si, the main impurities in the solutions before and after precipitation indicate a preferential partitioning of Ca and to a lesser extent Si and Fe into gibbsite.
Irradiation Induced Effects in the Environmental Scanning Electron Microscope
Authors: Stevens Kalceff Marion A
Published: July 2020

When a poorly conducting specimen is irradiated with an electron beam in a variable pressure electron microscope, the excess charge on the surface of the specimen can be neutralized by incident gas ions to prevent deflection and retarding of the electron beam. A small fraction (<10∼6) of the incident electrons are trapped at irradiation induced or pre-existing defects within the irradiated micro-volume of specimen. The trapped charge induces an electric field, which may result in the electro-migration and micro-segregation of charged mobile defect species within the irradiated volume of specimen. These charge induced effects are dependent on the density of trapping centers and their capture cross sections. In particular, evidence of these micro-diffusion processes can be directly observed in electron beam irradiated ultra pure silicon dioxide (SiO2) polymorphs using Cathodoluminescence (CL) microanalysis (spectroscopy and imaging). CL microanalysis enables both pre-existing and irradiation induced defects in wide band gap materials (i.e. semiconductors and insulators) to be monitored and characterized with high sensitivity and spatial resolution. Depth resolution is achieved by varying the electron beam energy.
Advances in Environmental Scanning Electron Microscopy: Semiconductor/Thin Fim Applications, Cathodoluminescence (CL) Spectroscopy, and Detector Quantum Efficiency (DQE) Comparisons.
Authors: Griffin Brendan J , Browne James R , Drouin Dominique , Scharf David
Published: July 2020

Charge Contrast Imaging (CCI) in the environmental scanning electron microscope (ESEM) has rapidly evolved to an important imaging technique for a range of materials. The investigation of the applicability of CCI to the examination of semiconductor and thin film (MCT) samples and devices has been highly successful. Dopant concentration and depth can be differentiated, as has been noted for variable pressure SEM. Quantification of concentration remains difficult due to the complexity of variables controlling CCI but should be achievable in the near future. The extreme sensitivity to surface contaminants previously noted on polished diamond surfaces is also seen on silicon. Monte Carlo modelling of this contrast indicates, for the examined materials, an information depth of a few nanometres for CCI, whilst using 30kV accelerating voltage. The modelling shows that CCI is capable of routine detection of contaminant layers on silicon at the nanometre scale. These results also provide the first data confirming initial suggestions that CCI is derived from the near-surface regions of the sample.

CCI examination of mercury cadmium telluride (MCT) devices has also provided images with new detail. This detail is currently being interpreted. Initial examination suggests an influence of the substrate on film growth (figure 1). Unusual corner structures are visible around the mask region.
Environmental SEM in a Multi-User Biological Sciences E.M. Unit
Authors: Gilpin Christopher J , Baguneid Mohamed S
Published: July 2020

Environmental scanning electron microscopy (ESEM) has matured into a mainstream technique in many areas of microscopy. Instrumentation has evolved and our understanding of some of the imaging mechanisms has progressed. However the majority of laboratories where ESEMs are located are based around the materials sciences. Despite the fact that ESEM is the only SEM instrument that permits liquid water to be present whilst imaging, the housing of such a microscope in biological EM units has been relatively rare. This authors laboratory is a multi-user EM unit based in a School of Biological Sciences. There exists the opportunity for basic biological scientists, clinical and pre-clinical medical and dental researchers to make use of such a resource. Indeed as the ESEM is housed alongside a conventional high vacuum instrument and a cryo high vacuum instrument there exists the ideal opportunity to carry out comparative studies.

This study will examine a range of biological samples using ESEM, cryo SEM and dry high vacuum SEM.
Evaluation of the Variable Pressure Correction Technique for X-ray Microanalysis in the ESEM
Authors: Carlton R A , Lyman C E , Roberts J E
Published: July 2020

The purpose of this study is to evaluate the variable pressure correction technique (VPCT) as a solution to the problem of extraneous x-ray peaks due to electron beam broadening in the chamber gas of the ESEM. The basis of VPCT is the observation that target x-ray counts decrease with increasing chamber pressure; whereas, x-ray counts due to beam broadening increase. If data are collected at two or more chamber pressures, the number of x-ray counts for an element can be corrected to that expected at zero gas pressure (high vacuum). Tests of NIST SRM 482 have shown EDS x-ray analysis in the ESEM (within the chamber pressure range of 1 to 8 torr) to have comparable accuracy and precision values to those of EDS in the traditional SEM. The samples used in the these studies, however, were quite large (ca. 500 μm in diameter) and so extraneous EDS peaks, due to the electron beam broadening effect of the chamber gas, were minimized.

The 60% Au / 40% Cu wire of SRM 482 was pressed into a hole in the surface of an Al specimen stub so as to produce a flat surface with a sharp interface between the wire and the stub. Spectra were collected at 5 and 150 μm from the junction of the wire and the Al stub at chamber pressures of 2, 4, and 8 torr.
The Computation of the Skirt in VP-SEM OR ESEM With Monte Carlo Simulations
Authors: Gauvin Raynald
Published: July 2020

It is well known that the interaction of the electron beam with the gas in the VP-SEM or ESEM generate the so-called skirt as a result of the elastic collisions between the electrons and the molecules. Since the electrons in the skirt hit the specimen far away from the electron beam, they degrade the resolution of the analyses performed in the VPSEM or ESEM. However, the magnitude and the shape of the skirt are still a matter of controversy despite the fundamental importance of knowing these two factors. In this context, a Monte Carlo program has been developed to simulate the interaction of the electron beam with a gas as a function of the gas composition, gas pressure, electron beam energy and working distance (in reality, we should talk of the total distance traveled by the electron beam in the gas). This Monte Carlo program used a single scattering approach considering elastic collisions only since energy loss is negligible owing to the low density of the gas. 10 millions electron trajectories have been simulated for each conditions.