bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Aluminum Flocs in Distribution Drinking Water Using Differential Interference Contrast (DIC), Transmission and Scanning Electron Microscopy (TEM & SEM) and Energy Dispersive X-Ray Analysis (EDXA)
Authors: Song Y , Stark A
Published: July 2020

Conventional water treatment plants that use alum (aluminum sulfate) as a coagulant have been dealing with the issue of residual alum carry over from the treatment plant into the distribution system. The basic product formed whe alum is added to water is aluminum hydroxide floc. This floc grows in size and density as it captures suspended particulates and then is settled out. Smaller floc aggregates that pass through the settling process are in the most part removed by sand filtration. However due to the amphoteric characteristics and solubility properties of aluminum alon with it’s many different compounds, carry over of aluminum compounds through the filter is a phenomena that is a great concern to the water industry. These residual aluminum compounds produce small hydroxide floes that coat the inner surfaces of distribution pipes causing head loss or increased energy requirements for water pumping.In addition phosphate compounds (poly and ortho blends) have recently been added to the distribution system to reduce the leaching and corrosion of lead and copper from pipes.
Monte Carlo Simulation of Electron Scattering for Arbitrary 3D Structures Using A Multi-Quadtree Geometry Representation
Authors: Schiebl CO , Ambrose V
Published: July 2020

In the semiconductor industry the importance of Computer Aided Materials Analysis (CAMA) is growing rapidly due to ever decreasing feature sizes on semiconductor wafers. Due to the fact that the excitation volume is often larger than the typical feature size on a processed state-of-the-art semiconductor wafer it was necessary to extend SeSAME, a Monte Carlo simulator for arbitrary 2- dimensional geometries, to be able to handle arbitrarily shaped 3-dimensional structures. This is achieved by using a so called multi-quadtree approach for the discretization of 3-dimensional geometries.

A multi-quadtree consists of several parallel arranged modified quadtrees. This means, an arbitrarily shaped 3-dimensional structure is divided into parallel slices of constant geometry in direction perpendicular to the quadtree plane. The number of such 2-dimensional slices and the thickness of these slices is solely limited by the available memory. Therefore, really 3-dimensional structures may be resolved in principal with any resolution.
Misfit Dislocation Core Structures At Ba0.5 Sr0.5TiO3 /LaAlO3 Interfaces
Authors: Gao H-J , Rafferty B , Chen CL , Singh RK , Pennycook SJ
Published: July 2020

The trend of replacing trench and stack capacitors in a dynamic random access memory (DRAM) with a planar configuration has stimulated the development of high dielectric constant materials with reliably low leakage current and high dielectric breakdown strength. In this regard, high dielectric constant materials, such as PbZrxTiyO3(PZT), BaTiO3, SrTiO3, PbTiO3, and BaxSr1-xTiO3, have been extensively investigated as dielectrics in the last few decades. Of these, the sol id-solution quaternary BaxSr1-xTiO3, (BST) combines the high dielectric constant of BaTiO3, with the structural stability of SrTiO3, is one of the most promising materials for DRAM cells in very large-scale integrated circuits. BST shows a paraelectric phase for x<0.7 at room temperature, which provides additional features such as no aging or fatigue effects from ferroelectric domain switching. However, so far, there have been few studies of the interfaces between BST and the substrates, particularly at the atomic-resolution level.
X-Ray Mapping of Bimetallic Catalysts in Mesoporous Silica
Authors: J. Keast Vicki , A. Midgley Paul , F.G. Johnson Brian , Meurig Thomas John
Published: July 2020

The small electron probe available in a scanning transmission electron microscope (STEM), when combined with X-ray energy dispersive spectroscopy (XEDS), enables the acquisition of 2D compositional maps with high spatial resolution and sensitivity. In addition to the spectroscopic information available, images sensitive to atomic number (so called Z-contrast images) can be acquired simultaneously using high-angle annular dark field imaging (HAADF). These capabilities make the STEM an ideal tool to study elemental distributions in catalysts containing 1-2 nm sized metal clusters within a support of low atomic number. The material examined in this work comprises of mesoporous silica in a honeycomb structure with channels of ˜3 nm diameter (designated MCM-41) in which nano-clusters of the bimetallic Pd6Ru6 have been introduced into the channels using metal-cluster carbonyls as precursors. Details of the specimen preparation are similar to that outlined by Shepard et al. for a Cu-Ru bimetallic catalyst.

Fig. 1 shows (a) a bright-field (BF) image, (b) a HAADF image and (c-f) X-ray elemental maps acquired on a VG 603 STEM, operated at 300 keV with probe size of ˜1.4 nm (FWTM) and probe current of ˜0.6 nA.
Quantitative Composition Maps of Magnetic Recording Media by EFTEM
Authors: Bentley J , Wittig JE , Nolan TP
Published: July 2020

Elemental mapping of Co-Cr-X based magnetic recording media at resolutions approaching 1 nm by energy-filtered transmission electron microscopy (EFTEM) can provide quantitative measurements of intergranular Cr segregation for correlation with magnetic properties and materials processing. The thin-film media present many challenges for EFTEM methods, such as diffraction contrast and closelyspaced edges. The goal of this work was to provide robust methods for mapping quantitative compositions in such materials. Results presented here are for a model material of 60 nm of Co84Cr12Ta4 on a 75 nm Cr underlayer; both films were d.c. magnetron sputtered onto a NiP-plated Al substrate pre-heated to 250°C. Other compositions and thinner layers (∼30 nm) have also been studied. EFTEM was performed on back-thinned, plan-view specimens with a Gatan Imaging Filter (GIF) interfaced to a 300 kV LaB6 Philips CM30. Optimized acquisition conditions have been detailed elsewhere. Besides core-loss image series, zero-loss I0 (slit width Δ=10eV), low-loss Ik (Δ=30eV), and unfiltered IT images were recorded, and maps of t/λ. = ln(IT / I0), where t is specimen thickness and λ. is the total inelastic mean free path, were produced.
An EELS-Study of the Chemical Homogeneity in Cu-In-S Films
Authors: Su DS , Schattschneider P , Zeitler E
Published: July 2020

The development of high-efficiency, low-price photovoltaic devices relies on epitaxially grown layers of ternary chalcopyrites. The question addressed in this study is to which extent the near stoichimetric composition of CuInS2 grown on hydrogen terminated Silicon, Si (111), varies cross the sample area. The method usually employed [1] for such analysis is Argon-Rutherford Backscattering (RBS), whose spatial resolution, however, is limited to the order of millimeters. This limit can readily be overcome by electron microscopic and electron spectroscopic means.

For observation and recording of the energy loss spectra in the transmission electron microscope, samples were carefully prepared by mechanic polishing and ion-milling. The thinning began with polishing the Si substrate on ALLED diamond lapping films, down to 10 μm and a final ion-milling in a Gatan ion-thinning equipment from the Si-side (Ar+ 3 kV, the incident angle less than 7°).Spectra were taken by means of a Gatan image filter (GIF - 100) in a Philips CM200 FEG electron microscope operated at 200 kV.
Jump Ratio Elemental Mapping in Amorphous Ice Cryo-EFTEM Opens the Window to Solution Chemistry
Authors: Bovin J-O , Huber T , Balmes O , Malm J-O , Karlsson G
Published: July 2020

The preparation of frozen amorphous thin films of solutions containing crystals, and imaging with cryo energy filtered TEM, opens for the first time the possibility to image the chemistry of solids interacting with liquids. The future possible areas of research include: dynamic of crystal growth processes, adsorption mechanisms, ion exchange, structure determination of solids in equilibrium with solutions, etc.

The sample preparation uses a controlled-environment vitrification system1. Vitrification of the liquid phase was achieved by plunging the grid into liquid ethane. The vitrified specimen was transferred into the microscope by an Oxford CT3500 cryo-holder. The specimen temperature in the microscope column can be kept at -−183 °C. The thickness of the vitrified films, including the crystals, should be about 250 nm or preferably less. The Philips CM120 BioTWIN Cryo, here used for cryo-TEM, has a focal length of 6 mm and a structural resolution of 0.4 nm.
Energy Filtering of Schottky Field Emission Gun Using Fringe Field Monochromator
Authors: Mook HW , van Veen AHV , Kruit P
Published: July 2020

The energy resolution which can be attained in electron energy loss spectroscopy (EELS) is determined by the energy spread of the electron source. The energy width of a high brightness electron gun (typically 0.4 to 0.8 eV) blurs the energy spectrum. A pre-specimen energy filter or monochromator must be used to reduce the energy width of the beam below 0.1 eV to allow detailed EELS analysis of the electronic band structures in materials. The monochromator can not only improve EELS, but it is also capable of improving the spatial resolution in low voltage SEM, which is limited by the chromatic blur of the objective lens. A new type of monochromator the Fringe Field Monochromator has been designed and experiments in an ultra high vacuum setup show the monochromatisation of a Schottky Field Emission Gun.
Z-Contrast Imaging and EELS Analysis of Chromium Doped Diamond-Like Carbon
Authors: Fan X , Dickey EC , Pennycook SJ
Published: July 2020

Diamond-like carbon (DLC) has attracted considerable interest with a variety of potential applications [1]. A new class of amorphous films has been produced recently by incorporating metals within the carbon network. The electrical conductivity of these films varies a wide range, however nonlinear with the metal concentration. It is believed it is because metals may form clusters. Such nano-phase metal cluster encapsulated by an inert matrix can offer interesting applications, for example as nano-electrodes used in electrochemistry[2]. It is therefore fundamentally important to observe the metal cluster formation. By using Z-contrast imaging [3], the metal distribution can be directly determined on the atomic level. The local metal concentration and other electronic properties cafi also be analyzed by spatial resolved electron energy loss spectroscopy (EELS)
Measurement of Effective Extinction Distances in Zone Axis Silicon
Authors: Yu Z , Vanfleet RR , Silcox J
Published: July 2020

Extinction distances for two beam conditions are readily available through many sources, but under more complex zone axis conditions extinction distances are not well known. The use of thickness fringes as an approximate thickness estimate under zone axis conditions, such as in high resolution Annular Dark Field imaging, can be a useful tool. We have measured thickness vs. fringe number under zone axis conditions using low loss Electron Energy Loss Spectroscopy (EELS). Work was done on the Cornell UHV HB501 STEM.

Several orientations of silicon were glued together and thinned in cross section by the wedge technique. Additional thinning was done by low angle ion milling. Surface oxide was removed with an HF etch before loading into the microscope.Each piece of silicon was tilted to the zone axis condition and low loss EELS spectra was taken at selected points. The thickness fringes were numbered with the following convention: the center of the first black fringes close to the edge is 1 and the center of the second black fringe is 2, etc.
Archie Howie Symposium : Celebrations in Pioneering Electron Microscopy
Authors: Gai PL , Boyes ED , Carter CB , Marks LD , Pennycook SJ
Published: July 2020

The first MSA Special Symposium honors Professor Archie Howie CBE FRS for his pioneering contributions to the physics and applications of electron microscopy, initially in TEM and more recently also for SEM; and his leadership, outstanding teaching and wide ranging collaborations in these and related fields.

Professor Howie’s important contributions have included fundamental studies of diffraction contrast effects in the TEM which have been extensively leveraged in numerous applications and collaborations, by Howie, his coworkers and many others. They have had a major impact in column approximations, an early discovery of the weak beam effect in many beam computer simulations of coherency strain contrast and subsequent advances in dislocation weak beam imaging, and the first identification of 311 planar defects in irradiated Ge. Inelastic scattering and particularly valence losses, electron channeling, optical potential and x-ray production, amorphous materials were all major contributions, as were the series of projects centered on novel STEM methods.
Extended and Point Defects in Diamond Studied With the Aid of Various Forms of Microscopy
Authors: Steeds JW
Published: July 2020

Introduction

There is considerable interest in CVD diamond layers for a wide variety of applications. Growth of high quality and phase pure material is now achieved in a number of laboratories but it remains to optimize the growth process for particular applications so that physical properties approaching or even exceeding those of the best natural diamond can be achieved. We have found that the combined use of a wide range of different microscopies is effective in the process of refinement.

Diamond quality and phase purity

Raman spectroscopy is widely used to investigate the phase purity of diamond layers. Infra-red Raman is particularly sensitive to the presence of traces of non-diamond carbon in diamond while ultra-violet Raman reveals the presence of traces of diamond carbon in layers that largely are not sp bonded. For thick rather perfect layers confocal micro-Raman mapping is a convenient method for revealing the locations of non-diamond regions.
Scattering Cross Sections in Electron Microscopy and Microanalysis
Authors: Rez Peter
Published: July 2020

In all scattering experiments some measure is need of the strength of the scattering interaction. The scattering cross section, which has dimensions of area, is a quantity that can be defined for any scattering interactions, irrespective of the nature of the scatterer, or the particle or radiation being scattered. To define a scattering cross section, refer to the geometry of Figure 1. If I0 is the incident number of particles, Is the number of particles scattered through an angle θ with an energy loss ΔE, N is the number of scatterers/ unit volume and t is the thickness of the specimen (or length of the scattering region) then where σ(θ,ΔE) is the scattering cross section. The product N t represents the number of scatterers per unit area as seen by the incident beam

In electron microscopy all scattering arises from the Coulomb interaction between the incident electron and the electrons or nuclei or the atoms in the specimen.
Low Voltage Scanning Electron Microscopy (LVSEM) in Perspective
Authors: Boyes ED
Published: July 2020

In the past quarter century low voltage SEM (LVSEM) has been developed for use in a wide range of applications, and it has become the main area of innovation in SEM, and now perhaps more widely in electron microscopy. The intellectual challenge (1,2) has been transformed into a vital tool of modern technology in the semiconductor, polymer and chemical industries, and is widely used in the materials and biological sciences (3, 4). It has been claimed by this author and others that LVSEM is the rational and preferred state of SEM, but unfortunately at the time of the first SEMs only higher voltage systems could be built with the technologies available half a century ago (1). The primary advantage of the SEM remains the use of real bulk specimens with a minimum of potentially invasive preparation. A wide area in the range of square mms to sq inches can contain aperiodic, or otherwise infrequent, events in or on the surface, or in a simple snapped cross-section, and always using relatively stable bulk samples.
Characterisation of Amorphous Materials By Electron Diffraction and Atomistic Modelling
Authors: Cockayne D J H , McKenzie D R , McBride W , Goringe C , McCulloch D
Published: July 2020

Disordered or ‘glassy’ materials are of significant technological value. Their structure can be investigated by diffraction (neutron, X-ray, electron) techniques. When the available volume is very small (eg thin films, non-homogeneous structures) only electrons are suitable. Cockayne and McKenzie developed a technique of RDF analysis using energy filtered electron diffraction which gives information on structures of amorphous materials through the reduced intensity function ϕ(s) and the reduced density function G(r). This technique has been applied successfully to many systems.

A major limitation to the use of G(r) for characterisation of amorphous materials arises from the fact that, for electron diffraction, the G(r) measured is a combination of all partial radial distribution functions for each species in the solid. In addition, in practice there are many different models which will equally well fit the data. In order to overcome these difficulties, refinement needs to be done using a realistic starting atomic configuration. For this reason, we have produced starting models using ab-initio molecular dynamics (Car-Parrinello scheme).
EELS Characterization of Electronic Structure in Group III - Nitrides Compared With Synchrotron Ellipsometry Results
Authors: Brockt G , Lakner H
Published: July 2020

EELS in the low loss region of the spectra (< 50eV) provides information on excitations of outer shell electrons and thus the electronic structure of a specimen material which determines its optical properties. In this work dedicated EELS methods for the experimental acquisition and analysis of spectra are described which give improved information about the electronic structure near the bandgap region at a spatial resolution in the range of nanometers. For this purpose we made use of a cold field emission STEM equipped with a dedicated EELS system. This device provides a subnanometer electron probe and offers an energy resolution of 0.35 eV. Application of suitable deconvolution routines for removal of the zero loss peak extracts information on the closest bandgap region while Kramers-Kronig transformation deduces the dielectric properties from the measured energy loss function. These methods have been applied to characterize the optical properties of wide-bandgap materials for the case of group Ill-nitride compounds which are currently the most promising material for applications on optoelectronic devices working in the blue and ultraviolet spectral range.
An Automated and Rapid Process for Determining Number of Atoms in Supported Ultra-Small Metal Clusters
Authors: Yang JC , Bradley S , Gibson JM
Published: July 2020

Since heterogeneous catalysis depends on surface chemistry, insights into the structure of supported catalytic materials is vital for understanding catalysis. We have developed a mass spectroscopic technique using very high angle annular dark field images in a scanning transmission electron microscope (STEM), that gives the number of atoms per cluster. We have also developed a robust interactive computer program to analyze these images rapidly. In this proceeding, we will present our method and results on analyzing ultra-small and dispersed Pt clusters on amorphous carbon, as well as our preliminary results of Pt on γ-A12 O3.

The ultra-small Pt clusters on the amorphous carbon Cu grid were made by a proprietary technique. Imaging for the STEM-based mass-spectroscopic technique was performed on a Field Emission Gun (FEG) VG HB601 STEM operated at l00kV. The absolute measured intensity from the clusters were converted to scattering cross-sections, which can then be converted to number of atoms: More details of this method can be found in Singhal, Yang and Gibson.
Direct Observation of Growth Behaviour of Athermal Omega-Phase Crystals in a Beta-Titanium Alloy Due to Cooling to 77k Using In-Situ Dark Field Imaging Technique
Authors: Matsumoto Hajime , Sukedai Eiichi , Hashimoto Hatsujiro
Published: July 2020

INTRODUCTION

It has been reported by many authors that metastable β-Ti alloys such as Ti-Nb, Ti-V and Ti- Mo indicate the negative temperature dependence of electrical resistivity at low temperature since Ames et al., found the dependence on Ti-Nb alloys in 1954. Williams et al., suggested that the phenomenon resulted from formation of athermal co-phase crystals. In order to clarify the origin, electron diffraction pattern analyses were carried out using a specimen cooling stage and both of start and finish temperatures of formation of athermal co-phase crystals were decided. However, it is necessary to reveal the morphology of athermal ω-phase crystals to study the relationship between the electrical resistivity change and appearance of athermal ω-phase crystals. On the other hand, although electron diffraction pattern analyses are able to identify the atomic structures of crystals, which appear the diffraction spots, it is not so easy to reveal the detailed morphology of the crystals. Also, it has to consider effects of electron irradiation to transformations.
Analysis of Extended Energy-Loss Fine Structure of Nanometerscale Clusters
Authors: Ito Y , Jain H , Williams DB
Published: July 2020

Small atomic clusters are of great importance for applications such as catalysts whose activity depends on the surface of the cluster. Attempts to determine the atomic short-range order and size of clusters have been made by analyzing the extended X-ray absorption fine structure (EXAFS). However, the analysis was made on an average of many small clusters. Analysis of extended energy-loss fine structure (EXELFS) in an electron energy-loss spectrum (EELS) has developed to the point where in some cases, the quality of the results is comparable to its X-ray analogue, EXAFS. No other technique provides nanometer-scale spatial resolution of the analyzed area for determining the atomic structure. Most EXELFS analysis has been performed on the K-ionization edge of lighter elements. For heavier elements, a more complex ionization edge such as the L-edge has to be used, due to the inefficiency of collecting high quality EEL spectra at higher energy-losses (Z > 18).
Theoretical Investigations of RHEED Oscillations
Authors: Mitura Z , Dudarev SL , Whelan MJ
Published: July 2020

Nowadays there is great interest in the application of reflection high energy electron diffraction (RHEED) to monitor the growth of ultra thin films. This popularity of RHEED arose from the discovery of RHEED intensity oscillations in the early eighties. Namely, it was experimentally found that if the growth of a material follows a layer-by-layer mode then regular oscillating changes in the intensity of the specular beam occur, and the period of the oscillations corresponds to the deposition of one atomic layer of the material. These findings are of great practical importance and consequently RHEED is an important experimental technique used in nanoscale engineering. Nevertheless, the basic question of why RHEED oscillation are observed still remains open. In the past the Philips group suggested that intensity oscillations are a consequence of periodic changes in the roughness of the surface. About the same time, the University of Minnesota group claimed that during the growth the electron wave is reflected by two terraces (in an idealised case) and periodic changes of the interference conditions imply RHEED oscillation.
Inner-Shell Damage Thresholds Below 1kv in Cu-Phthalocyanine
Authors: Chen Q , Spence J , Stevens M , Weierstall U
Published: July 2020

In 1970, Breedlove and Trammel predicted that, because of radiation damage, the direct imaging of individual organic molecules by electron or X-ray microscopy was not possible. This follows from an analysis, above IkeV, of the beam energy dependence of the ratio of inelastic scattering cross sections (some of which causes damage) to elastic cross sections (used to form the image). To minimize damage, we have therefore constructed a transmission electron microscope with nanometer resolution, which operates at 7 - 300 eV, below the threshold for most inelastic processes. Recently we have obtained our first images of TMV with this instrument. Isaacson first suggested that the K-shell ionization of carbon may be the most important damage process. Although less probable than valence excitation, it dumps more energy into the system, and the decay products are highly damaging. A subsequent study of electron beam damage in several π- bonded hydrocarbon crystals down to about 200 eV showed that a damage threshold does exist at about IkeV incident energy which can be explained by the carbon K-shell ionization. (Multiple scattering increases the energy threshold from 285eV).
Structural Fluctuations in Metal Nanoparticles
Authors: Tanaka Miyoko , Takeguchi Masaki , Furuya Kazuo
Published: July 2020

The structure of small particles attracts great interest for their distinctiveness. Small particles of several materials undergo lattice parameter change or crystal structure change and sometimes form multiply twinned particles (MTPs) [1]. Configurational and structural fluctuations which they show under electron beam irradiation are also interesting phenomena [2]. This quasi-molten state are well explained theoretically [3], but the exact cause of it is still a matter of debate [2,4].

To clarify the behavior of nanoparticles under electron beam more precisely, we grew indium, palladium and molybdenum nanoparticles on Si (110) TEM samples in situ and investigated with an ultrahigh vacuum field emission transmission electron microscope (UHV-FE-TEM). It is a JEOL-2000VF operated at 200 kV with a base pressure of the column less thari 2.0 x 1O−8 Pa. Two kinds of evaporators are attached to the column in order to perform in situ evaporation of metals; an electron beam (EB) evaporator for high melting temperature material and a thermal heating evaporator with tungsten wire for low melting temperature ones.
Visibility of Small Metalllic Catalyst Particles in High-Resolution Secondary and Backscattered Electron Images
Authors: Liu Jingyue
Published: July 2020

Metallic nanoparticles finely dispersed onto high surface-area supports play an important role in heterogeneous catalysis. The performance of a supported metal catalyst can be directly related to the size and spatial distribution of the metallic nanoparticles. With the recent development of highresolution SEM instruments, it is now possible to observe nanoparticles in a field emission SEM. At low voltages, surface details of catalyst supports as well as metallic nanoparticles can be observed. The particle contrast in low voltage SEM images, however, is still not well understood. We have previously shown that the contrast of metallic particles can be enhanced if a small positive potential is applied to the sample. It is suggested that backscattered electrons (BE) significantly contribute to the visibility of metallic nanoparticles in high-resolution SE images. In this paper, we report further study on the origin of particle contrast in high-resolution SE images.

Figure 1 shows a set of SE images of the same area of a carbon supported Pt catalyst.
Defect Structures in Semiconducting Resi2−x Epitaxial Thin Films
Authors: Misra A , Mitchell TE
Published: July 2020

Narrow band gap semiconductors such as ReSi2-x (Eg ∽0.12 eV) are potential materials for infrared detectors [1]. Further, ReSi2-x is in thermodynamic equilibrium and has a very small lattice mismatch with Si offering the potential of developing ReSi2-x /Si heterojunction devices where the detector element and the signal processing circuitry can be integrated on one Si chip. In a previous study, strong crystallographic alignment between ReSi2-x film and (001)Si substrate was observed by ion channeling [1]. In this study, a transmission electron microscopy (TEM) study has been performed on ReSi2-x epitaxial films on (001) Si. Comparisons are made to our previous microscopy study [2] on the defect structures in bulk single crystals of ReSi2-x.

ReSi2-x films were prepared by reactive deposition epitaxy (RDE) technique by evaporating Re onto (001) Si wafer at 650 °C. A cap layer of Cr was evaporated at room temperature. A bright field (BF) TEM image of the interface in cross-section is shown in Fig. 1 with the corresponding selected area diffraction pattern (SADP) shown in Fig. 2.
Analysis of Degraded Gold-Plated Surfaces in Contact With Lead-TiN Solder During Elevated Temperature Testing of 208- PIN Microelectronic Packages
Authors: Schaper Jake , Weberg Ron
Published: July 2020

This report provides analysis data on black deposits observed on gold-plated test socket pads. The socket pads are an integral part of a burn-in test where the test simulates an accelerated aging process and is routinely performed on new products. The test consists of placing a device, as shown in Figure 1, with lead/tin plated copper leads in a test socket then placing that assembly into a “burn-in” oven set to a specific elevated temperature, 150° C in this case, for a specific time. Typically, a bias voltage is applied through the pads on the socket during the test. Historically, during extended burn-in tests of Quad Flat Pack (QFP) devices, problems arose when several devices unexpectedly exhibited open socket-to-device contacts. The “opens” problem repeated itself when new QFP devices were installed in the sockets. Upon visual inspection of the sockets, black deposits were observed in the contact regions, as shown in Figure 2.
Control of Si-Island Free Ultra-Thin Simox Structures by Implant Energy and Oxygen Dose
Authors: Johnson B , Jiao J , Seraphin S , Yan T , Wilson T , Anc M , Cordts B
Published: July 2020

To serve the needs of future submicron electronic applications such as cellular communications and character recognition, the computational elements have to be drastically reduced in size as well as power consumption. A promising approach is based on implantation of oxygen ions into a silicon substrate and subsequent high temperature annealing. The process when properly done, results in a very thin silicon layer separated from the bulk silicon substrate by a thin layer of silicon oxide. In these SIMOX elements the top silicon layer is seriously degraded by defects introduced by the ion implantation process, consequently affecting the performance of devices built on them. A careful selection of processing parameters such as implant energy and dose is essential in order to minimize the defect densities. It is believed that Si interstitials are the main reason for the formation of most defects in SIMOX [1]. Consequently, the reduction of the implant oxygen dose minimizes the Si interstitials, and finally lowers the defect densities in both the top Si and buried oxide layers.
Interface Voids and Precipitates in GaAs Wafer Bonding
Authors: Vanfleet RR , Shverdin M , Zhu ZH , Lo YH , Silcox J
Published: July 2020

Wafer bonding allows the production of Compliant Universal substrates that are made by bonding a thin (< 10 nm) layer twisted ∼45 degrees to the underlying substrate. Subsequent growth on this twisted layer results in defect free films even when the growth material has a significant lattice mismatch with the substrate. Defects on the bonding interface are a common observation when bonding GaAs to many substrates, but the exact nature of these defects has not been clear. We have studied this bonding layer in GaAs-GaAs twist bonded structures by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy and established that the defects are voids with a portion being partially filled with gallium. Two general sizes of voids are seen. The larger voids are approximately 45 nm in diameter and 22 nm in the wafer normal direction and are distributed in an approximately linear relationship.
Transmission Electron Microscope Characterization of Siz Selective Deposition of Si-Nanoparticles
Authors: Wu Hai-Ping , Nishimura Kimihiro , Kebaili Nouari , Fujinuma Haruko , Takayanagi Kunio
Published: July 2020

Nanosized semiconductors have been highly desirable as optoelectronic materials since the discovery of photoluminescence from porous nanostructured silicon. There are many investigations about visible light emission from nanostructured semiconductors, and several studies showed the size dependence of the photoluminescent and electronic property [1], [2]. In order to investigate the size effect of those optical properties of nanoparticles, the size-selection technique is important.

Size-selection of silicon nanoclusters has been carried out by crossing, an Ar molecular beam perpendicularly to the silicon cluster beam. The laser ablation in inert gas method was used for fabricating nanometer-sized silicon. Large size silicon clusters are produced by Nd:YAG laser irradiation of a silicon wafer which was rotating in ablation chamber under He-gas flow. Produced nanoparticles were extracted through a nozzle ( ϕ = 0.6 mm) to a differentially pumped chamber and then skimmed into a high vacuum chamber for size selection and deposition.
TEM Study of Amorphous Silicon Recrystallization
Authors: K Lam Lawrence , Jiang Nan , G Ast Dieter , Silcox John
Published: July 2020

Recently there has been increasing interest in nickel induced lateral recrystallization of amorphous silicon because of its potential to improve device performance and to lower the thermal budget during processing. The hypothesis is that the formation of nickel silicide provides a low energy nucleus for the recrystallization of amorphous silicon. The silicide, moving into a-Si, leaves crystalline silicon behind.1 The grains formed, therefore, tend to elongated. In this paper, we attempt to use TEM to investigate in detail the nickel assisted lateral crystallization of amorphous silicon. The sample was prepared by first depositing a 1000A thick low temperature, oxide layer, LTO, on Corning 1737 glass. A 1000A thick amorphous silicon layer, a-Si, and 1000A thick a-Si were deposited subsequently. The sample was pattern and etched with hydrofluoric acid to form lOum x lOum holes in the oxide layer. Next, 200A of nickel was evaporated onto the sample, followed by a 600°C, 6 hours anneal to induce lateral recrystallization.
Transmission Electron Microscopy Observation of 11MEV B5+ Ion Irradiation in Bi2Sr2CaCu2O7-x Single Crystal
Authors: Zhou WL , Sasaki Y , Ikuhara Y , C.J.O’Connor
Published: July 2020

Artificial defects generated by ion irradiation have been considered an efficient method to enhance the critical current density in superconducting materials. The mechanism of producing defects as flux pining centers is still an important issue since the efficiency of irradiation-induced defects in flux pinning strongly depends on their microstructures. Different types of defects have been found in heavy ion irradiation. However, there are few results that show light ion irradiation due to the target material selected, the type of light ion and energy, and the incident ion angle. Another factor is the difficulty of cross-sectional sample preparation. In this paper, a single crystal Bi2Sr2CaCu2O7-x with 11 MeV B5+ ion irradiation was observed by transmission electron microscope (TEM) from both plan and cross-sectional view.

The Bi2Sr2CaCu2O7-x single crystals used for ion irradiation were prepared using the floating-zone melting method. The crystals were cleaved into thin sheets of about 20 μm thickness along the a-b plane and cut to about 2mmx2mm size.
Observation of an Elementary Cuboctahedron Of Xe Nanocrystal in an Al Matrix
Authors: W. Allen Charles , C. Birtcher Robert , Furuyat Kazuo , Songt M , E. Donnelly Steven , A. Ryan Edward
Published: July 2020

When a noble gas element such as Xe is implanted in an fee metal matrix such as Al at room temperature, a fine dispersion of precipitates forms. The precipitates are elementary fee crystals up to diameters of several nanometers (for Xe in Al, 8-10 nm), above which they are non-crystalline. The precipitates exhibit a cube-on-cube orientation relation with the matrices and have lattice parameters which are much larger than those of the matrices (axe ≃ 1-5aAl). Thus the interphase interfaces are incommemsurate though the lattices are isotactic. The precipitates assume the shape of matrix cavities; for an Al matrix, at equilibrium this is a cuboctahedron, a {111} octahedron truncated at the corners on {100}. Fig. 1 is a sketch of a dispersion of such cuboctahedra, viewed approximately along a <110>.

For this study specimens were prepared in the HVEM-Tandem Facility at Argonne National Laboratory by implanting 35 keV Xe to a dose of 4x1019 m−2 into well-annealed 5N Al discs which had been thinned by jet electropolishing.
AES and SEM/EDS Analysis of Silvered Teflon Laminates of Optical Solar Reflector
Authors: Wang Len , Kiwak Robert , Kauder Lonny , Greer Gregory
Published: July 2020

The Optical Solar Reflector (OSR) of Earth Observing System-PM (EOS-PM) is made of a flexible function layer of silvered Teflon/Inconel/Kapton laminate bonded to a honeycomb panel. After having been thermal cycled in vacuum, the laminate/panel was irradiated in air with UV at 2.2 equivalent suns intensity for 500 hours. Severe darkening was observed in areas exposed to UV but little or no darkening occurred in adjacent but shaded areas. Drastic increase of absorptance was observed-due to the darkening.

In order to investigate the cause of the degradation, test samples were irradiated at different configurations for 1000 equivalent sun hours (ESH). These samples were freestanding laminates and irradiated in vacuum and air, respectively. No darkening was observed on the sample that was irradiated in vacuum. Severe darkening was observed on the sample that was irradiated in the air. A laminate sample was irradiated in dry nitrogen for 1000 ESR and found no darkening either.
EELS and Xanes Analysis of Plutonium and Cerium Edges From Titanate Ceramics for Fissile Materials Disposal
Authors: Fortner JA , Buck EC , Kropf AJ , Bakel AJ , Hash MC , Aase SB , Chamberlain DB
Published: July 2020

We report x-ray absorption near edge structure (XANES) and extended x-ray fine structure analysis (EXAFS) spectra from the plutonium Llll and cerium Lm edges in prototype titanate ceramic hosts for disposal of surplus fissile materials. These spectra were obtained using the MRCAT beamline at the Advanced Photon Source (APS). The XANES and EXAFS results are compared with electron loss spectra (EELS) determination of oxidation state from the plutonium MlV,V and cerium MlV,V edges [1,2]. The titanate ceramics studied are based upon the hafniumpyrochlore and zirconolite mineral structures and will serve as an immobilization host, containing as much as 10 weight % fissile plutonium, and 20 weight % (natural or depleted) uranium. Similar formulations were composed using cerium as a “surrogate” element, replacing both plutonium and uranium in the ceramic matrix. We find the plutonium to be present almost entirely as Pu (IV), while the cerium is clearly in a mixed III-IV oxidation state in the surrogate ceramic.
Microstructural and Compositional Characterization of SiC-On-Insulator Structures
Authors: Ishimaru Manabu , M. Dickerson Robert , E. Sickafus Kurt
Published: July 2020

As the size of Si integrated circuit structures is continually reduced, interest in semiconductor-oninsulator (SOI) structures has heightened. SOI structures have already been developed for Si using oxygen ion implantation. However, the application of Si devices is limited due to the physical properties of Si. As an alternative to Si, SiC is a potentially important semiconductor for high-power, high-speed, and high-temperature electronic devices. Therefore, this material is a candidate for expanding the capabilities of Si-based technology. In this study, we performed oxygen ion implantation into bulk SiC to produce SiC-on-insulator structures. We examined the microstructures and compositional distributions in implanted specimens using transmission electron microscopy and a scanning transmission electron microscope equipped with an energy-dispersive X-ray spectrometer (STEM-EDX).

Figures 1(a) and 2(a) show bright-field images of 6H-SiC implanted with 180 keV oxygen ions at 650 °C to fluences of 7xl017 and 1.4xl018 cm−2, respectively. Three regions with distinct image contrast are apparent in Figs. 1(a) and 2(a), as indicated by A, B, and C.
Nanoindentation in Tin/Nbn Multilayers and Thin Films Examined Using Transmission Electron Microscopy
Authors: Lloyd SJ , Pitchford JE , Molina-Aldareguia JM , Barber ZH , Blamire MG , Clegg WJ
Published: July 2020

Nanoindentation allows the hardness of thin coatings and synthetic multilayer structures to be measured, since indentation depths can be as little as a few 10s of nm. In combination with the cross-sectional transmission electron microscopy (TEM) analysis described here it is possible to observe the deformation structure under an indent, and potentially to understand deformation mechanisms on a nm scale in a wide variety of materials. Synthetic multilayers are a particularly interesting system to investigate. Variations in hardness with the multilayer compositional repeat distance (A) have been reported for several systems. The highest hardnesses, which are in excess of what a simple “rule of mixtures” would predict, occur in nitride multilayers at A ∼5nm. Here we present some preliminary results showing the deformation structure in both a monolithic NbN film and a TiN/NbN multilayer in which both components have the rQck salt structure with lattice parameters 0.424nm (TiN) and 0.439nm (NbN).
Heterogeneous Formation of Oriented Silicon Oxynitride on α-Si3N4 Seed Crystals : Habits And Radiation Stability
Authors: Carpenter RW , Braue W , Kim MJ
Published: July 2020

Lath-like silicon oxynitride crystals have often been observed in the microstructure of silicon nitride based ceramics after processing. They are usually located in glassy regions which are siliceous solidified sintering aid liquid, and usually contain a small (∼100nm) a-Si3N4 crystal. These nitride crystals are considered to be seeds, incompletely dissolved in the melt, that are heterogeneous nucleation sites for the oxynitride crystals. We present here the first observations of morphological and crystallographic habits between the seed nanocrystals and the host oxynitride laths.

Fig. 1 shows a typical oxynitride lath containing a nitride seed crystal. The lath is surrounded by glass and ß-Si3N4 particles, and a small cristobalite particle (a minor constituent). This microstructure is from an Si02-Si3N4 ceramic processed with Al2O3 sintering aid. The same oxynitride lath/seed structures were observed when other sintering aids (eg. Y2O3, MgO, ZrO2) were used, so they are independent of sintering aid.
In Situ Observation of Ferroelectric Domain Motion in BaTiO3
Authors: Krishnan A , Bisher ME , Treacy MMJ
Published: July 2020

Ferroelectrics are used in many applications such as non-volatile memory, infrared detectors, phased array radar and optical switches. While substantial progress has been made in the development of commercial ferroelectric devices, we still do not possess a good understanding of the fundamental processes in ferroelectrics. Trapped charge and oxygen vacancies are believed to strongly influence domain motion. In order to study these issues, we have designed an in situ TEM holder that can subject ferroelectric crystals to voltage, heat and UV irradiation.

Bulk BaTi03 crystals, grown by the Remeika method, were mechanically polished and thinned in hot ophosphoric acid. The resulting thin flakes were attached to copper rings with conductive carbon paint and electrical wires were glued to the copper rings, which act as electrodes. The sample was placed in the cradle of the in situ TEM holder and examined in a Hitachi H9000NAR TEM.
Analytical Electron Microscopy of Composite Interfaces
Authors: Kim Steven , P. Dravid Vinayak
Published: July 2020

The fiber/matrix interfaces play a critical role in the mechanical performance of fiber-reinforced ceramic-matrix composites (CMCs). In this vein, the placement of an interphase material between the fiber and matrix phases has received considerable attention. The main purpose of the interphase coating is to enhance toughness of the composite by influencing crack trajectories at the mechanically critical (weak) fiber/coating interface.

This interest in coated-fiber composites has been accompanied by the need for accurate microanalysis of the CMC systems, owing to issues of both morphological and chemical incompatibilities between the dissimilar fiber and coating materials. Consequently, microanalysis has been driven below the micrometer scale, into the length scale of nanometers. Thus, the examination of the fiber/coating interfaces in CMCs falls squarely into the realm of transmission electron microscope (TEM) and scanning transmission electron microscopy (STEM) analyses.

However, the success of TEM/STEM-based microanalysis of CMCs hinges critically on the quality of TEM specimen.
Alchemi Analysis of Cation Distributions in Spinel-Structured Compounds Using Oxygen as a Marker Element
Authors: M. Anderson Ian
Published: July 2020

The establishment of ALCHEMI (atom location by channeling-enhanced microanalysis) as a viable microanalytical technique owes much to its early success in determining cation distributions in crystals having the structure of the mineral spinel, MgAl2O4. The first application of ALCHEMI was to a synthetic chromite spinel, and geological applications to natural mineral spinels containing multiple 3d transition elements provided many of the early applications of the technique. Spinel has three distinct regular lattice sites, two cation sites and one anion site, occupying the 8a, 16d and 32e Wyckoff positions of the Fd3m space group. In projection along (800), tetrahedrally coordinated (8a) cations occupy one set of alternate planes, whereas octahedrally coordinated (16d) cations and, to a good approximation, the anions occupy the other set. In principle, therefore, ALCHEMI performed at an 800 planar channeling condition could be used to analyze site distributions in spinel, using oxygen as a marker for the planes containing the octahedral cations, as was early noted.
Cation Coordination At Σ Grain Boundaries in TiO2 and SrTiO3, and its Effect on the Local Electronic Properties
Authors: Zaborac JA , Buban JP , Moltaji HO , Stemmer S , Browning ND
Published: July 2020

Grain boundaries have long been known to have a dominant effect on the electronic properties of polycrystalline materials. In the case of electroceramic oxides, the thermodynamics of defect formation (vacancies or interstitials, cations or anions) are usually invoked to predict the presence of a space charge potential at the grain boundaries. The relative energetics for the formation of each type of defect determines the size and sign of this potential barrier and thus, the effect that boundaries have on the overall electronic properties of the materials. However, a limitation to this continuum thermodynamics approach is that it does not consider the effect of the grain boundary structure.

To investigate whether the grain boundary atomic structure can have an effect on the energetics of defect formation and hence the electronic properties, here we examine the structure of Σ5 boundaries in two systems, SrTiO3 (perovskite) and TiO2(rutile).