bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Carbonaceous Phases in Interplanetary Dust Particles by Acid Dissolution of Microtomed Thin-Sections
Authors: Joswiak D J , Brownlee D E
Published: July 2020

Interplanetary dust particles (IDPs) collected from the stratosphere are grains of cosmic dust delivered from asteroids and comets. IDPs are composed of complex mixtures of carbon, silicate glass and submicron to nanometer-sized minerals including Fe-Mg silicates, Fe-Ni sulfides, oxides and metal. Bulk SEM and detailed TEM investigations of stratospheric IDPs in the size range of 5 - 15 μm have shown that many IDPs have remarkably high concentrations of carbon - essentially the highest carbon abundances of any known extraterrestrial materials - and often this carbon is intermixed at the nanometer scale with other constituent phases. in order to investigate the properties, occurrence and spatial distribution of carbon in IDPs, we have developed a unique aciddissolution technique using standard microtomed thin-sections to remove the silicate and oxide fractions, thereby leaving a residue primarily of carbon and Fe-Ni sulfides. This technique causes no damage to the delicate microtomed sections or TEM grid and dramatically minimizes the quantity of acids required for etching.
TEM Study of the Effect of the Sapphire Substrate Surface Orientation on the Microstructure of Tin Dioxide Films
Authors: Dominguez J E , Fu L , Pan X Q
Published: July 2020

Tin dioxide (SnO2) has been extensively studied and used as gas sensors to detect toxic gases such as CO, NOxand flammable gases like H2.[l] Recently, considerable researches have focused on thin film sensors due to their high performance as well as their integration compatibility with semiconductor technology for making microsensors and sensor arrays. [2] The performance of thin film sensors is remarkably influenced by the way they were fabricated.[3] Among various deposition techniques, pulsed laser deposition (PLD) has shown great prominence in the deposition of a wide variety of oxide thin film materials such as high Tc superconductors, semiconductors and dielectrics. in this work we present our experimental results on tin dioxide films deposited using pulsed laser ablation on sapphire (α -Al2O3) substrates with different surface orientations.

Tin oxide films with a thickness of 100 nm were deposited on the (1012) and (0001) sapphire by pulsed laser ablation of ceramic SnO2 targets.
Misfit relaxation in SrTiO3/SrRuO3 bilayer films on LaA1O3(100) substrates
Authors: Wu JS , Jia CL , Urban K , Hao JH , Xi XX
Published: July 2020

Besides perfect dislocations, partial dislocations were proposed as effective means for misfit relaxation in the heretostructure system [1]. The microstructure of SrRuO3 films on SrTiO3 and LaA1O3 substrates have been studied. While misfit dislocations could be hardly found at the SrTiO3/SrRuO3 interface [2], high density of defects was observed in the SrRuO3/LaA1O3 interfaces [3]. in this paper, we report the high-resolution electron microscopy study of the SrTiO3/SrRuO3 bilayer films on (100) LaA1O3 substrates. The emphasis is focused on the means of misfit relaxation at the two interfaces.

Figure 1(a) is a low magnification cross-sectional image of a two-layer SrTiO3/SrRuO3 film on LaA1O3 taken along the [110] direction of the substrate. A high density of defects were observed along the SrRuO3/LaA1O3 interface. Figure 1(b) is a quarter of a superposed electron diffraction pattern (EDP) from the SrTiO3/SrRuO3 interface area, while fig. 1(c) is from the SrRuO3/LaA1O3 interface area.
Characterization of Magnetron Assisted Pulsed Laser Deposited ZrO2-Au Composite Films Using TEM and EDS
Authors: Hu JJ , Voevodin AA , Zabinski JS
Published: July 2020

Microstructurally engineered oxide coatings have good potential as lubricants for aerospace applications over a wide range of environmental conditions1. Using composite microstructures, wear rates and friction coefficients may be reduced compared to monolithic coatings. Here, we report the characterization of ZrO2-Au composite coatings as new candidate lubricants. Au is added to ZrO2 to reduce friction and improve toughness. The composite films were grown on steel and silicon disks at room temperature (RT) by pulsed laser ablation of a ZrO2/5 wt. % Y2O3 target, with simultaneous operation of a magnetron source to add Au. The laser beam was operated at 250mJ, 40 Hz, and the magnetron was operated at 1.5-3.5 W cm-2 in 2.7 Pa argon. Varying the magnetron power produced coatings with different concentrations of Au. The coatings were prepared for transmission electron microscope (TEM) analysis by tripod polishing and ion milling on a cold stage.
In-Situ Growth and Polygonization of Epitaxial Passive Oxide Films on Nanoparticles of Iron
Authors: Fung KK , Zhang XX , Kwok YS , Qin Boxiong
Published: July 2020

Over the years, the study of the oxidation of nanoparticles of iron by transmission electron microscopy (TEM), Mossbauer spectroscopy and X-ray diffraction has established that nanoparticles of iron have a core-shell morphology in which the iron core is enclosed by shell of polycrystalline shell of ultrasmall γ-Fe2O3 and Fe3O4 crystallites. Recently, passivated nanoparticles of iron prepared by gas condensation of plasma evaporated vapor in Tianjin University exhibit remarkable resistance to further oxidation and corrosion in air and water. We have showed by TEM that these nanoparticles of iron are protected by a 4 nm epitaxial shell of γ-Fe2O3. The epitaxial orientation relationship, established by convergent beam electron diffraction from a nanoparticle, is as follows:

The [001] diffraction pattern of the oxide is rotated by 45° about a cubic axis relative to that of iron.
Analyses of The Eutectoid Phase Transformation in Complex Ds Nb-Silicide In-Situ Composites
Authors: Sitzman SD , Bewlay BP
Published: July 2020

In-situ composites based on (Nb) and Nb silicides, such as Nb5Si3 (tI32 crystal structure) and Nb3Si (tP32 crystal structure), are being investigated for revolutionary high-temperature structural applications [1,2]. The use of Hf and Ti alloying additions to these silicides has also been examined; in these systems Nb5Si3 has also been observed with the hP16 structure. The present paper describes EBSD analyses of a directionally solidified (DS) Nb-silicide based composite that experienced a eutectoid transformation. The composites were directionally solidified using the Czochralski method as described previously [1]. The composites were creep tested at 1200°C for 24 hours. Microstructure and microtexture characterization were performed using scanning electron microscopy, and electron backscatter diffraction pattern analysis (EBSD).

The microstructure of a composite directionally solidified from a Nb-12.5Hf-33Ti-16Si alloy is shown in Figure 1. in the as-DS condition the microstructure consisted of primary (Nb)3Si dendrites and coarse (Nb)3Si-(Nb) two-phase cells.
Inclusion Characterization and Bubble Evolution in Doped Molybdenum Wire
Authors: Iorio LE , Larsen M , Bewlay BP
Published: July 2020

Previous studies on aluminum-potassium-silicon (AKS) doped tungsten wire have shown that the dispersion which provides the interlocking grain structure in recrystallized tungsten wire is bubbles of elemental potassium. However, there is little previous work on the K-containing dispersion in doped Mo. This paper will describe analyses of doped Mo.

The creation of dopant inclusions in Mo powder and generation of K bubbles in doped Mo wire both prior to and following various heat treatments has been studied. The effect of doping Mo with K, Al and Si is to increase the recrystallization temperature of the Mo and to produce a microstructure of coarse, interlocking grains after recrystallization.

Mo wire is produced in a similar manner to AKS doped tungsten, however lower processing temperatures are typically used in the production of Mo wire. The dopants are added to Mo oxide powder as potassium silicate and aluminum chloride.
The Geometric Compatibility Factor Determining Brittle Crack Propagation Across Boundary in Bainitic Low Alloy Steels
Authors: Oh Yong-Jun , Kim Min-Chul , Hong Jun-Hwa
Published: July 2020

Boundary properties between two adjacent grains with different crystallographic orientation relation are important factors in deciding the mechanical properties of materials. in our previous reports, we introduced the geometric compatibility equation as a factor determining the brittle crack propagation condition into the adjacent grain in banitic low alloy steel as follows:

M = cos α · cos θ

where α is the angle between crack normal in the cracked grain-I and normal to (001) plane in the adjacent grain-II and θ is the angle between normal to (001) plane in the grain II and loading axis.(see FIG. 1) Higher M gives greater possibility to the crack propagation. The geometric compatibility factor (M) could be easily calculated from the crystallographic data obtained from Electron Backscatter Diffraction (EBSD) analysis, and successfully predicted actual crack propagation plane. We also found that there was a critical M value to arrest the brittle crack propagation at the boundaries.
RMS Strain 〈ε〉½ Variation Vs Grain Refining During Annealing of Co50Ti50 Synthesized By AM-SPS
Authors: Martínez-Sánchez R , Béjar-Gómez L , Espinosa-Magaña F , Cabañas-Moreno JG , Duarte Moller A , Diaz de la Torre S
Published: July 2020

The mechanical alloying (MA) process has been probed to be an effective method to conveniently develop materials with novel structures. The products of MA can be processed by conventional powder metallurgy routes for further consolidation. However, the novel features conferred to the powders, such as fine crystal size and chemical homogeneity can be lost during sintering operations, due to the high chemical activity of some of the synthesized phases. The Spark Plasma Sintering (SPS) process is an alternative route to obtain highly dense MA′ed products while retaining these novel microstructures, including a metastable state. Advantages of the SPS process over conventional sintering processes are the fast heating and cooling rates, and the high pressure applied. Combining these two material processing techniques (MA and SPS) it is possible to obtain materials with interesting (far from equilibrium) microstructures. Co-Ti alloys were obtained by MA and SPS, as described in related publications.
Initial Oxidation Kinetics of Copper (110) Thin Films As Investigated By IN SITU UHV-TEM
Authors: Zhou Guang-Wen , D.Bharadwaj Mridula , C.Yang Judith
Published: July 2020

In the study of metal oxidation, there is a wide gap between information provided by surface science methods and that provided by bulk oxidation studies. The former have mostly examined the adsorption of up to ∽1 monolayer (ML) of oxygen on the metal surface, where as both low and high temperature bulk oxidation studies have mainly focused on the growth of an oxide layer at the later stages of oxidation. Hence, we are visualizing the initial oxidation stages of a model metal system by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM), where the surfaces are atomically clean, in order to gain new understanding of these ambiguous stages of oxidation. We have previously studied the growth of Cu2O islands during initial oxidation of Cu(100) film. We are presently investigating the initial stages of Cu(110) oxidation, from 10−4 Torr O2 to atmospheric pressures and temperature range from room temperature to 700 °C.
In-Situ Study of NiO Growth on Textured Nickel Tape Using Environmental Scanning Electron Microscope (ESEM) and Hot Stage
Authors: Akin Y , Goddard RE , Sigmund W , Hascicek YS
Published: July 2020

Deposition of highly textured ReBa2Cu3O7−δ (RBCO) films on metallic substrates requires a buffer layer to prevent chemical reactions, reduce lattice mismatch between metallic substrate and superconducting film layer, and to prevent diffusion of metal atoms into the superconductor film. Nickel tapes are bi-axially textured by cold rolling and annealing at appropriate temperature (RABiTS) for epitaxial growth of YBa2Cu3O7−δ (YBCO) films. As buffer layers, several oxide thin films and then YBCO were coated on bi-axially textured nickel tapes by dip coating sol-gel process. Biaxially oriented NiO on the cube-textured nickel tape by a process named Surface-Oxidation- Epitaxy (SEO) has been introduced as an alternative buffer layer. in this work we have studied in situ growth of nickel oxide by ESEM and hot stage.

Representative cold rolled nickel tape (99.999%) was annealed in an electric furnace under 4% hydrogen-96% argon gas mixture at 1050°C to get bi-axially textured nickel tape.
TEM Characterization of Corrosion Initiation in Passive Films
Authors: Elswick D , Hren J , Kotula P , Missert N , Wall F
Published: July 2020

This research program is intended to develop new insight into the mechanisms of localized corrosion initiation in passive metals through unique approaches based on examining corrosion initiation on needle-shaped samples similar to field emitter tips. Samples with this geometry allow localization of corrosion initiation to the tip itself and therefore pit initiation can be confined to a small lateral area. Local electric fields can also be controlled, thus permitting damage to be confined in the passive over layer, and characterized before pit initiation.

High purity Al wire was used for the initial studies. Wire shaped specimens were electropolished in a 20 % perchloric in methyl alcohol solution at -30°C to obtain the fine needle geometry. The resultant tip radii ranged from 40 to 150 nm with no further sample prep needed and without the presence of artifacts.A custom-designed TEM holder for a Philips CM30 was fabricated, which allowed the needles to be characterized by TEM both prior to and after experiments.
Microstructure of Copper Films and its Oxides Prepared by Electron Beam Evaporation and ECR Plasmon Oxidation
Authors: Campin MJ , Barbour JC , Braithwaite JW , G. Zhu Jane
Published: July 2020

The corrosion of copper is an important area in materials science because of the widespread use of copper in structural devices and electronics. These widespread uses in conjunction with its thermodynamic instability in most atmospheric conditions have prompted numerous atmospheric copper corrosion studies. The goal of these investigations has been to identify the underlying mechanisms by which corrosion proceeds in order to prevent any detrimental corrosion effects. Despite these studies, the microstructure of copper and its oxides remains poorly understood. Therefore, our investigation is concentrated on determining this microstructure.

In our investigation, copper films are electron-beam evaporated onto SiO2 coated Si wafers and then exposed to an electron-cyclotron-resonance (ECR) O2 plasma, which simulates an aggressive oxidizing environment. The ECR-grown oxide is fully oxidized to CuO at the surface and changes to CU2O further into the sample. The thickness of the oxide layer is controlled by the sample exposure time to the ECR plasma.
Photon and Electron Beam Induced Phase Transformations in CDS Nanocrystals
Authors: Gajdardziska-Josifovska M , Lazarov V , Reynolds J , Yakovlev V V
Published: July 2020

One of the great challenges of nanotechnology is how to produce and modify objects at nanoscale dimensions. The search for physical and chemical methods for controlled synthesis, modification and characterization of semiconductor nanocrystals is of special interest due to their novel electronic and optical properties. Recently we have achieved the first laser-induced phase transformation in semiconductor nanocrystals [1], irradiating colloidal solutions of CdS nanocrystals with 7 ns pulses of 532 nm wavelength. We used established wet-chemistry methods to synthesize the CdS nanocrystals, and a combination of electron microscopy methods to determine the structure, size and composition of the nanocrystals. In the present paper we report a wavelength dependence of the laser-induced phase transformations in CdS. We also explore electron-induced transformations in comparison with their photon counterparts.

Aqueous colloidal solutions of CdS nanocrystals were prepared by mixing of CdCl2 with Na2S in the presence of Sodium Mercaptoacetate and HC1 [2].
Characterization of Magnetically Aligned Single Wall Carbon Nanotubes Using Transmission Electron Microscopy
Authors: Smith Brian W , Luzzi David E
Published: July 2020

The ability to align single wall carbon nanotubes (SWNTs) is paramount for harnessing their remarkable anisotropic electronic and mechanical properties. D.A. Walters et al. (Rice Univ.) have succeeded in aligning milligram quantities of SWNTs using a strong magnetic field. The nanotubes were aligned in suspension and simultaneously filtered to produce a thin membrane. However, small angle X-ray scattering (SAXS) — the traditional technique for obtaining fiber patterns — has proven ineffective in determining the degree of alignment due in part to carbon's weak atomic scattering factor for X-rays.

In the present work we succeed in quantitatively characterizing this membrane using transmission electron microscopy (TEM). A self-supporting sample was prepared by peeling ∼ 0.5 mm long strips from the material. TEM images reveal that the membrane itself is not a single, large bundle (i.e. rope) of SWNTs. Instead, it has a prominent texture, corresponding to many ropes aligned parallel to the direction of the applied magnetic field.
Statistical Significance of Discrete Soot Particulate Microanalysis
Authors: Bell David C
Published: July 2020

Soot particles are generated from a number of sources, including auto emissions, aircraft emissions and various domestic and industrial combustor sources. Particle size and composition has been the focus of recent Environmental Protection Agency directives, especially due to the impact of small particulates on the inner urban environments. Single particle microanalysis is advantageous in these studies since, morphology and composition can be examined simultaneously. When a small sample size is available, single particle microanalysis is the only possible micro analytical approach. Chemical fingerprinting using the energy dispersive x-ray spectroscopy (EDS) signature of trace elements contained in the particles has shown remarkable source based uniqueness. Previous studies involving diesel soot particulates have indicated that most samples analyzed on a discrete basis are reasonably homogeneous, but questions still remain as to the ultimate statistical limit of this technique.
Initial Kinetics of Copper Oxidation in Different Oxidizing Atmospheres as Studied by In Situ UHV-TEM
Authors: Bharadwaj Mridula D , Tropia Lori , Gibson Murray , Yang Judith C
Published: July 2020

It is of fundamental and practical interest to understand the oxidation process since a desirable property for metals is resistance to corrosion. But there is a wide gap between information provided by surface science methods and that provided by bulk oxidation studies. The former have mainly examined the adsorption of ∼ 1 ML of oxygen on the metal surface, where as both low and high temperature bulk oxidation studies have mainly focused on the growth of an oxide layer at the later stages of oxidation.

We are probing the initial oxidation stage of a model metal system by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM) in order to gain insights into the initial kinetics of oxidation. We have previously shown that the growth mechanism of the cuprous oxide is initially dominated by oxygen surface diffision.
Metastability in co-Tiintermetallic Compounds Sintered by SPS.
Authors: Martínez-Sánchez R , Espinosa-Magaña F , Cabañas-Moreno J G , Bejar-Gómez L , Díaz de la Torre S
Published: July 2020

The mechanical alloying (MA) process is an effective method to develop strategic materials with novel structures. These can be solid solutions (even in immisible systems), amorphous phases, fine particle sized and nano-metric crystals etc. Conventional powders metallurgy routes can process the mechanical alloyed products. However, the novel features conferred into the powders, can be lost during the sintering operations. The spark plasma sintering process (SPS) is an alternative route to dense mechanically alloyed products at a high grade while retaining their novel structures. Co-Ti alloys were produced by mechanical alloying the elemental powders mixtures with nominal composition Co50Ti50 (at. %). Details on the preparation and characterisation of the milled products can be found in related publications. Densification of the powders products was conducted using a Dr. Sinter equipment. Previous studies on Co-Ti alloys processed by MA and SPS have shown that the final products are composed of mixtures of metastable intermetallic compounds.
Inverse Porous Nickel Nanostructures From Opal Membrane Templates
Authors: Zhou WL , Xu L , Frommen C , Baughman RH , Zakhidov AA , Malkinski L , Wiley JB
Published: July 2020

Currently there is a strong interest in fabricating nanoporous metal arrays using various template methods. Porous opal membranes of close-packed silica beads, for example, have a unique template structure due to their tetrahedral and octahedral interstices. Such structures can be infiltrated with a variety of materials, especially metals, to form continuous inverse networks. Interest in these forms comes from their potential application in a variety of areas including photonics, magnetics, catalysis, and thermoelectrics. In this paper, we present electron microscopy characterization of inverse nickel photonic materials prepared by electrodeposition method.

Electrodes were formed from opal pieces (typically 7 x 10 x 1.5 mm with silica spheres about 300 nm) by first depositing about 0.5 micron thick copper films on one side of the piece with magnetron sputtering. A length of wire was then attached to the copper backing with silver paste.
TEM Study of Copper Oxide Nano-Particles in Silica Glass Prepared by Co-Implantation of Copper and Oxygen Ions
Authors: Wang S X , Nakao S , Wang L M , Miyagawa Y , Miyagawa S , Ikeyama M
Published: July 2020

The formation of nano-particles in silica glass by ion implantation has attracted great attentions because of the applications for visible luminescence and nonlinear optical devices. Ion implantation is a unique technique for producing nano-particles, with the advantages of high controllability of beam position, depth and distribution of projectiles, concentration, high purity and ability to overcome low solubility restrictions.

Optical grade silica glasses were used as the substrates. Ion implantation was performed with a 1.7 MV tandem-type ion accelerator (NEC 5SDH-II pelletron accelerator) of NERIN. The substrates were implanted with 1.0 MeV O+ and 1.8 MeV Cu+. Projected ranges were calculated by SRIM-2000 to be 1.5 μm (for O+) and 1.4 μm (for Cu+). Samples were cooled with liquid nitrogen to reduce the beam heating. The ion current densities of O+ and Cu+ were 6 and 2 μA/cm2, respectively.
From Dynamics to Details: Live-Cell Light Microscopy and Highresolution (25 nm) Soft X-Ray Microscopy
Authors: Larabell C A , Yager D , Meyer-Ilse W , Rowning B A
Published: July 2020

Imaging cells using a variety of microscopy techniques has generated information about the organization of cells and subcellular structures that is the foundation for understanding cell function. Invaluable information about the dynamics of cells has been obtained from a variety of light microscopy techniques, and the exquisite structural details of cellular organization have been obtained from electron microscopy. Each of these approaches, however, has its limitations. The resolution provided by light microscopy is limited by the wavelength of light, whereas the specimen preparation required for examining cells using electron microscopy is extremely tedious and time consuming. We show that soft x-ray microscopy can bridge the gap between these two forms of microscopy by providing a method for examining whole, hydrated cells up to 10 um thick at 25 nm resolution. Examination of rapidly frozen cells provides information that closely approximates that seen in living cells.
Troponin-Tropomyosin Control of Thin Filament Activity Revealed by Electron Microscopy and 3-D Reconstruction.
Authors: Lehman W , Hatch V , Rosol M , Korman V , Horowitz R , Van Eyk J , Tobacman L S , Craig R
Published: July 2020

Muscle contraction and the actomyosin ATPase that drives the contractile process are switched on and off by changes in sarcoplasmic free Ca2+ -concentration. In skeletal and cardiac muscles, on-off switching is mediated by the actinassociated protein tropomyosin and by the troponin complex. While the details of this mechanism are still subject to debate, it is well-accepted that tropomyosin strands move to sterically block and unblock myosin binding sites on actin, thereby controlling actomyosin ATPase and consequently contraction. It is also well known that the Ca2+- dependency of the movement of tropomyosin on actin is governed by troponin.

As a means of studying tropomyosin movement and the influence of troponin, we have used cryo-EM, negative staining and 3-dimensional helical reconstruction to define the positions of tropomyosin and troponin on thin filaments. We examined various preparations of native isolated filaments and filaments reconstituted with wild-type and mutant proteins.
Microscopy of Muscle in the 19th and 20th Centuries
Authors: Huxley Andrew F
Published: July 2020

In the 19th century, the microscope was the principal tool of biologists. The ordinary light microscope is designed to work on specimens that absorb light, but most unstained biological specimens do not absorb light appreciably and almost nothing is visible when such a specimen is viewed with the full aperture of the objective illuminated. However, they do show appreciable differences of refractive index, corresponding to variation in the concentration of solids, and the 19th century microscopists understood how to interpret the image when these were made visible by reducing the illuminating aperture and going slightly out of focus. If the objective is brought closer to the specimen (low focus), regions with high refractive index appear dark (positive image), and it became customary to use this setting, as in Fig. l (upper). As a result, the A bands of striated muscle fibres, with refractive index higher than the I bands, came to be known as the dark bands, although they appear bright with high focus.
Electron Microscopy and Excitation-Contraction Coupling. A Tribute To L.D. Peachey
Authors: Franzini-Armstrong Clara
Published: July 2020

Muscle contraction is activated by delivery of calcium from the internal membrane system of muscle cells, the sarcoplasmic reticulum (SR), to the myofibrils. Muscle relaxation ultimately depends on the sequestering of calcium back into the SR. In general, skeletal muscle is the most efficient in holding on to its calcium and calcium movements across the surface membrane are minimal during muscle activity. Cardiac muscle is less efficient and its activity is accompanied by significant movements of calcium across the surface membrane. Understanding of the calcium movements during muscle activation has relied heavily on structural information using the electron microscope and Lee Peachey was at the forefront in establishing structure function correlations. He talked the physiologists language and thus caught their attention.

Four stages can be detected in the contribution of EM to the unraveling of the calcium story. First the membrane systems involved were identified, and quickly sorted into two types on the basis of structural characteristics dictating specific functions.
X-Ray Microanalysis in the STEM
Authors: Williams D B , Watanabe M
Published: July 2020

Commercial TEM/STEMs are ill designed for quantitative X-ray microanalysis of thin foils. There have been no fundamental advances in their design since the first instruments appeared in the mid- 1970s. These instruments had thermionic sources with useful probe sizes of ∼10 nm, small (∼ 0.1 sr) detector collection angles, illumination systems giving serious levels of stray radiation, substantial hydrocarbon and water-vapor contamination due to the poor vacuum (∼10-5Pa) and sliding o-ring seals on unstable side-entry goniometer stages. The instruments lacked a direct measure of the probe current at the specimen. Often a 60 s accumulation time resulted in enough drift or contamination that the microanalysis was not trustworthy and spatial resolution was compromised. Today's modern TEM/STEMs, apart from replacement of thermionic source with a FEG, are little better.

Dedicated STEMs however, have invariably offered better X-ray performance. The first VG HB 5 DSTEM became available, also in the 1970s, and the X-ray performance improved through to the latest design (the VG HB 603) in the mid-1990s.
High Spatial Resolution Analytical Investigation of InGaAs/GaAs Quantum Dots
Authors: Catalano M , Crozier P , Taurino A , Passaseo A , Cingolani R
Published: July 2020

The improvement of growth techniques in the characterization of semiconductor nanostructures, has recently resulted in the realization of quasi-zero dimensional semi-conducting devices (quantum dots) of excellent performances and of reproducible quality (1,2). The design and fabrication of these devices strongly depends on the ability to control parameters that influence the quantum confinement namely the shape, dimension and size distribution of the dots. High spatial resolution structural and analytical techniques are crucial to obtain nanoscale information about the shape of the dots, the structural and chemical abruptness of the interfaces, and the composition of the dots (3).

In this paper we show the results of a structural and chemical characterization of In0.5Ga0.5As/GaAs quantum dots grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) on a (100) GaAs substrate. The growth was performed in a horizontal LP-MOCVD system (AIXTRON 200 AIX).
Comparison of Elemental Detection Using Microcalorimetry, SIMS, AES and EDS (SEM, STEM, and TEM)
Authors: Vartuli C B , Stevie F A , Wollman D A , Antonell M , Irwin R B , McKinley J M , Shofner T L , Purcell B M , Anderson S A , To B
Published: July 2020

Cu contamination has become a larger concern as more semiconductor fabrication facilities switch from aluminum to Cu interconnects. The resolution limits of several analytical tools are compared to determine the optimum analysis methods for detecting Cu contamination in semiconductor materials. The elemental detection limits of Secondary Ion Mass Spectrometry (SIMS), Auger Electron Spectrometry (AES), Microcalorimetry and Energy Dispersive Spectrometry (EDS) systems on Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM) instruments are evaluated for Cu in WSix.

Two different samples were used in this study. One sample has a high uniform concentration (0.9% atomic, 0.7 wt.%) of Cu that was incorporated during the sputter deposition of WSi2. A lower concentration was ion implanted with 63Cu to a dose of lel4 cm-2 and has a peak concentration of lel9 cm"3, or 0.02% atomic.
A Tilting Procedure to Enhance Compositional Contrast and Reduce Residual Bragg Contrast in EFTEM Imaging of Planar Interfaces
Authors: Moore KT , Stach EA , Howe JM , Elbert DC , Veblen DR
Published: July 2020

When acquiring energy-filtered TEM (EFTEM) images of a crystalline material, the detrimental effects of diffraction contrast can often be seen in raw energy-filtered images (EFI) (i.e., pre-edge and post-edge images), jump-ratio images and elemental maps as residual diffraction contrast. Residual diffraction contrast occurs in raw EFI because of plural scattering (i.e., inelastic-elastic and elastic-inelastic electron scattering) and in jump-ratio images and elemental maps because background removal procedures often are unable to completely account for intensity changes due to dynamical effects (elastic scattering) that occur between pre-edge and post-edge images acquired at different energy losses.

It is demonstrated in these experiments that, when examining a planar interface, EFTEM images have increased compositional contrast and decreased residual diffraction contrast when the sample is oriented so that the interface is parallel to the electron beam, but not directly on a zone axis.
Spectroscopy and Imaging With Energy-Filtering Tems: Parameters That Matter
Authors: Kothleitner G , Brink H A
Published: July 2020

Spectroscopy and imaging techniques based on electron energy-losses (EELS), which are accessible through energy-filtering transmission electron microscopes (EFTEMs), have proven to be important tools in both materials and life science investigations.

The two most widely used techniques on commercially available EFTEMs are elastic imaging and elemental mapping. Elastic imaging enhances image resolution and contrast by extracting the zero-loss signal and eliminating the inelastic background, whereas elemental mapping, which involves signals coming from element-specific inner-shell ionization edges, is employed to form two dimensional elemental distribution images. In both cases relatively large energy windows of a range of 10 to 30eVare typically used to form energy-filtered images with usually low to moderately high magnifications.

There is however much more information available in an EELS spectrum, which is contained in the detailed fine structure within 0-20eV of a core excitation edge (ELNES) or in the very low energy-loss up to 5eV.
Using Electron Energy-Loss Spectroscopy (EELS) To Study Rare Earth Elements In Natural Crystals
Authors: Xu Huifang
Published: July 2020

Because of similar chemical properties of the rare earth elements (Ree), whole series of the Ree may occur in natural Ree-bearing crystals. Relative concentration of the Ree may vary as the crystallization environments change. Electron energy-dispersive spectroscopy (EDS) associated with TEM is unable to resolve Ree and other coexistence elements, such as Ba nd Ti, because of peak overlap and energy resolution (∼ 150 eV) of EDS. Figure A indicate multiple peaks from Ce only. The Cu peaks are from Cu grid holding the specimen. Electron energy-loss spectroscopy (EELS) with energy resolution of < 1 eV is able to resolve all Ree in natural Ree-bearing crystals.

Natural carbonate crystals from a Ree ore deposit were investigated by using EELS associated with field emission-gun (FEG) TEM. The crystals are in a chemical series of BaCO3 - Ree(CO3)F [1]. In Figure B, EEL spectra A and B are from Ce-rich and La-rich bastnaesite (Ree(CO3)F), respectively; spectrum D is from cordylite (BaCO3 (Ree(CO3)F); spectrum E is from huanghoite (BaCO3 Ree(CO3)F), spectrum F is from BaCO3; spectrum C is from an unknown Ree-rich phase.
Low Energy Electron Transmission Through Thin Polymer Films
Authors: Kuhlman W , Libera M , Gauthier M
Published: July 2020

While transmission and beam damage have been well documented in the TEM at high accelerating potentials, considerably less is known about these phenomena at lower accelerating potentials. Imaging using low accelerating potentials may be attractive as an analytic technique, because chemical degradation associated with electron beam irradiation in organic macromolecules may be a function of accelerating potential (e.g. 1, 2). The present work examines low-energy electron transmission through thin polymer films and beam damage produced by low energy (∼ 0.5-10 keV) electrons.

Thin films of polystyrene were prepared by allowing a ∼ 0.005% solution of G3-5k arborescent polystyrene in toluene to evaporate on a holey carbon film. In solution, this arborescent polystyrene consists of spherical molecules of order 45 nm in diameter (3). When evaporated from dilute solution on a holey carbon film, monolayer thick self-assembled membranes form in some of the holes (figs. 1 and 2). The resulting films are highly reproducible in thickness and have a relatively uniform morphology (fig. 3).
Polymerization and Three Dimensional Reconstruction of Deoxy-Sickle Cell Hemoglobin Fibers in High and Low Phosphate Buffers
Authors: Wang Zhiping , Kishchenko Gregory , Chen Yimei , Josephs Robert
Published: July 2020

The amino acid substitution (B Glu → G6 Val) results in the conversion of Hemoglobin A (HbA) to sickle cell hemoglobin(HbS) which is responsible for sickle cell disease. Under physiological conditions this substitution causes a reduction of the solubility of HbA from about 340 mg/ml to 165 mg/ml (for HbS). One consequence of the reduction in solubility is that HbS polymerizes to form long fiber like structures about 240Å in diameter. The formation of these fibers causes sickle cell disease. The fibers fill the red cell and cause it to assume a characteristic sickle shape. More significantly the fibers cause the red cell to become rigid and, as a result, sickled cells can block blood flow in the capillaries. Understanding the polymerization process in detail is important for understanding the pathophysiology of sickle cell disease and for developing a specific therapy that could be used in its treatment.
Insulin Receptor: Structure Via 3D EM Reconstruction, Crystallography and NMR Reveals Details of Ligand Binding and Mechanism of Transmembrane Signalling
Authors: Ottensmeyer FP , Luo RZT , Beniac DR , Fernandes AB , Yip CC
Published: July 2020

For over 25 years a major effort in electron microscopy of macromolecules has been the determination of the three dimensional structure from the two-dimensional electron micrographs of such specimens. Great success has been realized when the macromolecule or complex takes the form of an array such as a 2D crystal (1,2), a helical structure (3,4) or one with icosahedral symmetry (5,6). However, for molecules which do not form such arrays, and in the limit only exist as single particles, a number of challenges have had to be addressed. No easy averaging of noisy low dose images is possible due to the lack of lateral and rotational symmetry. Random unknown orientations of the particles have to be determined, a process exacerbated by noise if low dose images are used as input. Alternatively, higher dose images result in radiation-induced structural alterations of the macromolecule.
Metal Coating Techniques for Contrast Enhancement of Biological Macromolecular Complexes In HRSEM, STEM and TEM Image Modes
Authors: Apkarian RP , Lee TAT , Conticello VP
Published: July 2020

Modern field emission SEMs fitted with in-lens or near-lens (W.D. = l-3mm.) stages and above-lens SE detectors are capable of imaging 1-5 nm features at high voltage (15-30kV) and 5-10 nm features at low voltage (l-5kV). Ultrathin fine-grain refractory metal coatings were shown to optimize higher-solution (HR) secondary electron imaging of light element specimens especially biological samples. Ambient temperature dried specimens and frozen-hydrated cryo-specimens coated with continuous 1nm-thick metal films and staged in-lens have revealed biologically significant features of molecular dimension in tandem HRSEM and scanning transmission (STEM) modes. Although positive and negative stains have proved useful for general contrast enhancement of TEM specimens these stains alter many of our new genetically synthesized block protein copolymers. Therefore we have turned to non-evaporated metal coatings for contrast enhancement of these specimens in the TEM.
Localization of Green Fluorescent Protein Absorbance by Energy Filtered Transmission Electron Microscopy
Authors: Davis J A , Garces R G , Diao J-Y , Ottensmeyer F P
Published: July 2020

Energy filtered transmission electron microscopy has the potential to provide high resolution, spatially resolved, atomic and chemical information. However, aberrations generated by the electron spectrometer blur the energy resolution and limit the atomic or molecular distributions that can be studied. Energy absorptions corresponding to the visible light range fall below an energy loss of 5 eV. The selection of electrons that have lost an amount of energy corresponding to chromophore absorption by the sample thus requires a spectrometer with a high energy resolution over the full image plane. A corrected prism-mirror-prism filter that has a resolution of 1.1 eV, sufficient to select these low energy loss electrons, was developed and installed by us in a Zeiss EM902. Its imaging capability was verified for a number of different chromophores. The chromophore currently under study is that of the green fluorescent protein (GFP).
Application of Atom Probe Microanalysis for Understanding Microstructure Evolution in Nickel Base Superalloy Welds
Authors: Babu S S , David S A , Miller M K
Published: July 2020

The characterization of the microstructure evolution during welding of nickel base superalloys is required for efficient reuse and reclamation of used and failed components. Previous atom probe analysis of electron-beam and laser-beam welds revealed complex alloying elemental partitioning between the γ and γ phases. Rapid cooling conditions in the weld leads to non-equilibrium partitioning and large amplitude Cr and Co levels in the γ phase. These results indicated that there is a strong relationship between weld cooling rate and the precipitation of γ′ precipitates from the γ phase. To understand and develop predictive models, a systematic investigation of the microstructure evolution in CM247DS alloy under controlled thermomechanical conditions are being performed. This paper describes some recent results on the elemental partitioning between γ and γ′ phases obtained with atom probe microanalysis.
Maxwellian Charge on Ferroelectric Domain Walls in KNBO3
Authors: Krishnan A , Treacy M M J , Bisher M E , Chandra P , Littlewood P B
Published: July 2020

Ferroelectrics are now being used as non-volatile memories, infrared detectors, phased array radar and optical switches. Although the development of commercial ferroelectric devices has advanced in recent years, we still do not have a clear understanding of the basic physics underpinning the behavior of actual ferroelectric devices. 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. Preliminary results on BaTiO3 have been presented in previous reports.

In this study, bulk KNbO3 crystals were mechanically polished and thinned in hot orthophosphoric 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.
Migration of Sodium in Feldspar by Electron Beam - An Experimental Study
Authors: Natarajan R
Published: July 2020

Quantitative analysis of Na in minerals like feldspar in an Electron Probe Micro Analyser (EPMA) confronts two problems - the first one arising at the time of data acquisiton of Xrays of Na (say Kα) and the second one during conversion of measured xray intensity ratios into true concentration while using certain correction procedure The fall in the count rate of Na xray signals as a function of time under stationary electron beam in EPMA is quite well known. This was attributed to volatilization of Na during electron bombardment. Another explanation for this phenomenon has been that Na+ ions made mobile in the crystal lattice of feldspar by the electron beam, move away from the point of its impact. This results in the fall in the count rate of Na with a corresponding increase in me count rate of matrix element like Si, Al.
Automated Focus of the Microprobe (Z) Using the Optical Signal
Authors: Delisle N , Grillon F , Thiot JF
Published: July 2020

The human eye is very sensitive to fuzziness and can hardly bear seeing blurred images. This situation is still worse for X-ray microanalysis as a defect in focussing the electron beam can induce errors in intensities (in reference 1, a focus deviation of 10 micrometers causes an error of about 5% due to the modification of the Bragg angle). While a human operator can easily modify the Z stage position depending on the optical image seen on the monitor, several hours-long acquisition sessions require an automated way of reproducing the operator behavior.

The basic principle is to use the optical signal delivered by the camera installed on the probe at different Z values, extracting for each step a simple characteristic in the image. The characteristic chosen is the standard deviation of the grey levels, which is easily computed from the histogram moments of order 1 and 2, and should be at its peak value (lowest value on Transmission Electron Microprobes) on the focussed image.
Lorentz TEM Investigation of Magnetic Domains in Epitaxial C-Axis Oriented Co-Cr Thin Films
Authors: Kusinski Greg J
Published: July 2020

Continuous increase in recording densities of the Co-based longitudinal media requires a drastic scaling down of the grain size in order to keep the required signal to noise ratio. However, this approach to increase the areal density will collapse when the grain size reaches the superparamagnetic limit. As an alternative, based on the analysis of the demagnetization mechanisms, Iwasaki and Takemura suggested the possibility of perpendicular magnetic recording (PMR), and computer simulation, predict areal densities of more than 300Gbit/in for this configuration. The c-axis oriented Co-based hep alloys with the magnetocrystaline anisotropy larger than the demagnetizing energy, are good candidates for the PMR media. However, before this type of materials can be realized, the magnetic domain structure must be well characterized. In this paper detailed analyses of the characteristics and shape of the magnetic domains present in the c-axis oriented CoCr films with thickness relevant for the recording industry are discussed.
Interfacial Mismatch and Interface Structure of Epitaxial Pb(Mg1/3Nb2/3)O3 (90%)- PbTiO3 (10%) Relaxor Thin Films
Authors: Yang G Y , Nagarajan V , Wang Z L , Li Y H , Ramesh R
Published: July 2020

Pb(Mg1/3Nb2/3)O3 (PMN)- and its solid solution with PbTiO3 (PT) is one of the lead-based relaxor ferroelectrics and has been the most widely studied materials because of their high dielectric constants and high electrostrictive coefficients. The potential impact of the thin film ferroelectric relaxors in the integrated actuators and sensing applications has stimulated research on the growth and characterization of thin films. Thin films have been made by pulsed-laser deposition (PLD), sol-gel and metalrganic chemical-vapor deposition. It is known that electrical properties may be strongly influenced by the microstructure of films and the interface structures between different phase in such heterostructure systems. In this paper, we report the investigation of interfacial mismatch and interface structure of epitaxial Pb(Mg1/3Nb2/3)O3 (90%)- PbTiO3 (10%) relaxor thin film by high resolution transmission electron microscopy (HRTEM).

Thin film capacitors of Pb(Mg1/3Nb2/3)O3 (90%) - PbTiO3 (10%) (PMN-PT) were grown by PLD on (100)-oriented LaA1O3 (LAO) substrates. La0.5Sr0.5CoO3 (LSCO) layer was deposited as electrode. Cross-sectional transmission electron microscopy samples were prepared following the traditional procedures including cutting, gluing, polishing and ion milling.