bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fixation artifacts in transmission electron microscopy
Authors: Bowers Blair 
Published: June 2020

Cell and tissue preparations for transmission EM contain artifacts introduced at each step of the preparative method. Fixation, as a first and crucial step, is subject to both gross and subtle artifact. For familiar tissues, gross artifacts are easily recognized. Artifacts in unfamiliar cells and subtle distortions or alterations of structure or localizations of molecules of interest are more difficult to assess.Three general approaches are useful for identification of fixation artifacts. Especially in the case of single cells, it is possible to make direct comparison of living and fixed specimens. Advanced light microscopic methods allow very high-resolution imaging of cells and comparison of structure before and after fixation. Light microscopic observation during fixation has documented examples both of creation of structure and disappearance of structure. A more widely applicable approach is the comparison of structure in the same tissue after fixation by different procedures.
Characterization of the low accelerating voltage performance of a microchannel plate based detector system for scanning microscopy
Authors: Cochran Raymond F. 
Published: June 2020

The Galileo SEM2000 microchannel plate (MCP) detector collects onaxis symmetrical secondary electron images at accelerating voltages as low as 200 eV and beam currents less than 5 picoamps. Symmetrical images are particularly useful in metrology and for viewing features that are shielded by topology from an off-axis detector. Backscatter images from the same on-axis orientation can be obtained at accelerating voltages below 500 eV and beam currents less than 10 picoamps.The ability to image secondary and backscattered electrons in the same orientation, together with extremely high detection efficiency for low energy electrons make it a valuable tool for direct analysis of beam-sensitive or dielectric samples. Additional topographic enhancement can be obtained by A-B signal processing at accelerating voltages as low as 200 eV.
Cryo-Scanning tunneling microscopy of DNA
Authors: Harris John , Partridge Aaron , Partridge Joshua , Nielsen Randy 
Published: June 2020

Scanning tunneling microscopy has found increasing interest in biological sciences. Several problems face the investigator imaging samples of biological origin. These include low conductivity, poor attachment of the sample to substrate and thermal/mechanical drift of the sample while scanning. Several approaches have tried to overcome these problems. These include coating with metal, freeze drying and/or freeze fracturing and tunneling in water. Another useful method is to freeze the sample on the STM holder and image frozen. The biological structure should stay rigid under the scanning tip, should not be swept away from the substrate and should provide highly reproducible images.Calf thymus DNA (Sigma #D-1501) was mixed in deionized water-tween 20 (0.1%). DNA concentrations varied between 10 μg/ml and 1 μg/ml. The sample was heated slightly, a small drop placed on highly oriented pyrolytic graphite (HOPG) and air dried. The sample holder was immediatel) placed in an Atomis variable temperature cryo-STM with a 6 micron scan range head (Surface Interface, Inc., Mountain View, CA), frozen and scanned.
Role of HVEM for in situ studies in materials science: The microlaboratory
Authors: Allen Charles W. , Westmacotp Kenneth H. 
Published: June 2020

With the development of the Atomic Resolution Microscope (JEOL ARM-1000) about a decade ago and the current availability of new ultra high resolution HVEMs, the important role of HVEM in high resolution imaging has been well achieved. Higher spatial resolution imaging is attainable with higher energy electrons without sacrificing sample tilting capability by virtue of a smaller CSλ value. When commercial HVEMs first became available in the mid 1960's, however, it was not the prospect of high resolution imaging which seemed most important but rather the fact that, for a given material, significantly thicker specimens could be examined.The microstructures (ultrastructures) and physical behavior of these foils (up to 15 μm thick) would be more representative of those for the bulk material. And especially for materials science applications two other factors were also of paramount importance: (1) the controlled generation of vacancy-interstitial (Frenkel) pairs in crystalline pure elements and alloys by high energy electron irradiation became possible and (2) the increased working space in the objective lens region allowed some miniaturized experimental apparatus to be incorporated.
The effect of specimen tilt on back-scattered electron image contrast in scanning electron microscopy
Authors: Meng-Burany X. , Curzon A.E. 
Published: June 2020

The present work concerns the back-scattered electron image contrast of a thin film of Cu64Mo36 on a silicon substrate. The contrast is defined by the ratio(1)where If and Ib are the backscattered electron signals from the film and from an adjacent bulk reference specimen. In previous work on thin sputtered films of Cu-Mo, Cu-W and Cu-Al both the film and the bulk reference specimen were perpendicular to the incident electron beam. It was found that the dependence of r on the accelerating voltage of the electron beam could be used to obtain both the thickness and the composition of the films. It is the purpose of the present work to determine whether the simple method previously used to extract the required information can be extended to include tilted specimens. As will be seen the method can be adapted to films tilted by less than 50°.
Optimized images of immunogold markers with backscattered electrons
Authors: de Harven Etienne , Ackerley Cameron , Leung Richard , Christensen Hilary 
Published: June 2020

The use of colloidal gold markers of small diameter (≤5nm) may permit direct quantification of the numbers of labeled molecules expressed on cell surfaces. To achieve this goal direct immunolabelina must be used and an imaging mode chosen which will revealALLthe present gold markers, i.e. baokscattered electron imaging mode (BEI). Baokscattered electron detectors resolving one nm gold particles have recently been described and immunoconjugate prepared with Fab fragments of TgG molecules will further increase labeling efficiency for more accurate quantitative studies.Meanwhile, it is desirable to optimize imaging of 5nm gold markers in the BEI mode, using conventional scanning electron microscopes. To that effect, we have been labeling cells with gold particles of two distinct sizes. 5 and 10 nm. The presence of 15nm particles facilitated fine tuning of the SEM in the BET mode for subsequent Imaging of the 5nm markers. We have compared two types of SEMs.
Heterogeneous nucleation of Ti2AlC precipitates at γ-TiAl grain boundaries in a Ti-52A1-3C alloy
Authors: Xiao S. Q. , Foitzik A. H. , Pirouz P. , Heuer A. H. 
Published: June 2020

Defects like dislocations and grain boundaries usually serve as preferred sites for nucleation of both coherent and incoherent precipitates. The catalytical effect of these defects are different for different kinds of precipitates. The purpose of this paper is to present a TEM observation of heterogeneous nucleation of Ti2AlC (α) precipitates at some special grain boundaries in γ-TiAl.A Ti-52A1-3C alloy fabricated at the University of California, Santa Barbara was annealed for 100 h at 1528 K and then creep tested for about 20 h at 1255 K. Thin foils were cut from the crept sample using a diamond saw and 3 mm discs were cut using an ultrasonic cutting machine. The discs were ground to 200 μm thickness from both sides. Final thinning was done by jetpolishing in a 10% HC104 and 90% CH3OH solution at 250 K and 40 V. The specimens were examined with a Philips EM400T microscope operating at 120 kV.
Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels
Authors: Advani A.H. , Murr L.E. , Matlock D. 
Published: June 2020

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.
On the disappearance of fine, disc-like features from thin foils of steel
Authors: Thompson S. W. 
Published: June 2020

Fine carbide particles form in quenched-and-aged specimens of iron containing a small amount of carbon. Similar precipitation occurs in ferrite grains within dual-phase steels. The particles have been described as discs or loops, typically about 20 run in diameter and 2 nm thick, which lie on ﹛100﹜ planes within ferrite grains. The precipitates are believed to form in association with vacancies and produce increases in hardness and yield strength. Two studies showed that these features disappeared after heating specimens in the transmission electron microscope (TEM), and this note reports further on this phenomenon.Continuously annealed and cold-rolled sheet steel (provided by Inland Steel Company) contained (in wt pet) 0.087 C, 0.97 Mn, 0.27 Si, 0.034 Al, 0.008 S, and 0.005 N. Specimens were intercritically annealed at 770°C for five minutes and quenched in iced water. Tensile testing was conducted within one day of heat treatment, and then specimens were stored at room temperature for about six months. Thin foils were produced by conventional thinning methods and jet polished at 75 V and 80 mA in an electrolyte containing 95% acetic acid and 5% perchloric acid. Specimens were examined in a Philips EM400 operated at 120 kV.
A Transmission Electron Microscopy examination of the effect of post-weld heat treatment on spot welded Ti-14Al-21Nb
Authors: Acoff V.L. , Griffin R.D. , Janowski G.M. , Radhakrishnan B. , Thompson R. G. 
Published: June 2020

Titanium aluminides have great potential in structural, aerospace, and high temperature engineering applications. In the majority of these uses, it is expected fusion welding will be used as the primary method of joining. However, control of the as-welded microstructure (and mechanical properties) is difficult to obtain since cooling rates and, therefore, the microstructures can vary considerably.Samples of 14.2 Al, 21.3 Nb, 0.018 C, 0.05 Fe, 0.012 N, 0.013 H, and 0.10 O (in wt.%), commonly known as Ti-24Al-11Nb (in at.%), were placed on a copper block and spot welded inside of a Iucite box using a gas tungsten arc welder (GTAW). The specimens were then sealed in argon backfilled fused quartz tubes and heat treated in the α2, + B2 field of the phase diagram. The conditions of this post-weld heat treatment (PWHT) were 982°C for 0.5, 1, 2, or 4 hours. Transmission electron microscopy and microhardness tests were used to characterize the alloy.
The role of the electron microscope in the cold fusion controversy
Authors: Murr L.E. 
Published: June 2020

More than two years ago, thousands of scientists around the world raced to confirm the claims of electrochemically induced fusions especially in the palladium/deuterium system. Interestingly enough, it was also claimed during the 1920's that ordinary hydrogen absorbed in palladium fuses to form helium.The author has recently argued that a significant feature of the controversy involving palladium electrodes in electrochemical systems where either hydrogen or deuterium absorption is crucial, probably depends strongly on the palladium microstructure. indeed there is no compelling evidence that has involved a systematic evaluation of the palladium metallurgy or specific microstructural alterations which may have been correlated with heat generation or other fusion-related phenomena.
Atomic force microscopy of mica surface after ion replacement
Authors: Dixon Northern B. L. , Chen Y. L. , Israelachvili J.N. , Zasadzinski J.A.N. 
Published: June 2020

Atomic Force Microscope (AFM), is the newest, and potentially most powerful of the scanning probe microscopes. The (AFM) is capable of resolutions approaching atomic dimensions on ideal surfaces. One of the favorite such surfaces is that of mica. Muscovite mica has a platelike structure consisting of an octahedral alumina sheet sandwiched by two tetrahedral silicate sheets. As a result of this structure, mica cleaves readily along a plane leaving a molecularly smooth surface. Because of the isomorphous substitution of the tetravalent silicon by trivalent aluminium, mica has an excess negative surface charge.This negative surface charge of 2.1-1014 charges per cm2 is neutralized by an equal number of positive monovalent ions, mainly potassium ions. The ion-exchangable surface ions of mica, in aqueous solution, can be readily replaced by other monovalent or multivalent ions. This ion exchange alters the surface of the mica. We then follow these changes by imaging with the AFM in air.
REM observations of oxygen-annealed rutile (001) surfaces
Authors: Liu J. , Wang L. , Cowley J. M. 
Published: June 2020

Rutile (single crystal TiO2) is widely used in electrochemistry, photochemical energy conversion and photocatalytic reactions of gases as a catalytic material. It is important to characterize the surface properties of rutile in order to understand its catalytic behavior. The rutile (001) surface is extremely unstable, forming facets on annealing as revealed by the LEED results. In this paper we report some preliminary results on the investigation of oxygen annealed rutile (001) surface, obtained by reflection high energy electron diffraction (RHEED) and reflection electron microscopy (REM) techniques.The crystal was cut into strips, finely polished, cleaned and chemically etched in NaOH and H2SO4 before annealing. The samples were annealed in pure oxygen at 1473 K for 36 h. The purposes of annealing the samples in pure oxygen are to preserve surface stoichiometry and to prevent surface reactions with elements other than oxygen during the annealing process. The RHEED and REM observations were performed in a Philips 400T microscope operated at 120 kV.
Compositional analysis of mercury zinc telluride by EDS and WDS
Authors: Price M. W. , Zuo H. , Janowsk G. M. , Andrews R. N. 
Published: June 2020

Semiconducting alloys of II-VI compounds have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities in II-VI materials can adversely affect device performance. Extensive work has been conducted to evaluate the influence of growth parameters on the compositional redistribution in directionally solidified bulk alloys. Energy Dispersive Spectroscopy (EDS) has proven to be a valuable tool both in evaluating the compositional homogeneity of II-VI alloys and gaining information about the influence of growth parameters on compositional redistribution.In the work reported here, samples of directionally solidified mercury zinc telluride (MZT) were analyzed by SEM/EDS. The specimens were prepared by longitudinal sectioning, polishing to a 0.25 am finish, chemical polishing with a 2 vol% bromine/methanol solution, and rinsing with distilled water, acetone, and ethanol. Standards of Zn, Te, ZnTe, and HgTe were prepared in a similar manner for the quantitative analysis.
Microstructural dependence of magnetic properties of Pt/Co multilayers for magneto-optical recording devices
Authors: Li Z.G. , Carcia P.F. 
Published: June 2020

Pt/Co ultrathin multilayer films are a new candidate for magneto-optical (MO) recording devices. We have previously shown that their magnetic properties are improved by sputtering them with either Kr or Xe instead of Ar. Specifically, Arsputtered films have too small coercivity for recording. In this study we demonstrate that high resolution electron microscopy (HREM) is a powerful technique to study the relationship of the multilayer microstructure and magnetic properties. We used a Philips CM30 and a JEM 2000FX microscope to study multilayers with a typical total thickness in the 10 nm range, consisting of only 1-2 atomic layers of Co and 4-6 atomic layers of Pt.Figure 1 compares the cross sectional microstructure of nearly identical Pt/Co multilayers (~10x[4Å Co+13Å Pt]) sputtered in (A) 7 mTorr of Ar, (B) 7 mTorr of Kr, and (C) 5 mTorr of Xe. The layers sputtered in Ar are extremely flat and continuous. Sputtering with a larger mass gas (Kr or Xe) progressively increased the layer roughness, and the lateral continuity of layers was more frequently interrupted by grain boundaries, which were very distinct in Kr- and Xe-sputtered films compared to Ar-sputtered films.
Transmission electron microscopy applications in integrated circuit processing
Authors: Kim Ki-Bum , Ritz Ken , Raaijmakers Ivo 
Published: June 2020

The present demand for higher integration density in IC processing with submicron design rules and the development of new materials require a routine application of highly sophisticated characterization techniques as regards both failure analysis and materials development. One such an example is the utilization of conventional and high resolution transmission electron microscopy (TEM) in an IC processing environment. In this paper, we summarize several examples of how TEM can support various IC development programs.Trends in modern IC processing require the formation of thin, high quality, epitaxial layers with abrupt, well-controlled dopant transition profiles. One of the key factors in achieving such an epitaxial layer is the maintenance of a clean surface during the deposition. Surface residues such as oxygen and carbon form SiO2 and SiC particles during layer deposition and, thereby, lead to the formation of a poor quality epitaxial layer.
Hexagonal phase in tensile low-pressure CVD poly-Si film
Authors: Nguyen Tai D. 
Published: June 2020

Polycrystalline silicon (poly-Si) films have found many applications in integrated circuits, and in actuators and sensors. Important considerations in the processing of these devices are structural stability and repeatable mechanical properties of the films. The texture and stress state of the films depend strongly on the microstructures and morphology of the films. Tensile films, which are preferred to compressive films in devices whose lateral dimensions of clamped structures are not to be restricted by compressive buckling, are characterized by equiaxial grain morphology, while compressive films are characterized by columnar grain growth during deposition.A diamond hexagonal (d.h.) Si structure with lattice parameters of a = 3.8Å and c = 6.28Å was first reported in 1963. More recently, transformation from the diamond cubic (d.c.) Si to the hexagonal phase has been observed in Si under hydrostatic pressure at temperatures between 350 C and 700 C, in heavily ion-implanted silicon, and in as-grown, implanted, and annealed CVD Si thin films, in addition to the known high pressure Si phases.
The study of compound semiconductor heterostructures by High-resolution transmission electron microscopy
Authors: Cullis A.G. 
Published: June 2020

Heteroepitaxial compound semiconductor systems have increasing importance for the fabrication of advanced electronic devices. Microstructural characterisation of the finest features of these materials can be carried out using transmission electron microscopy (TEM) and this paper demonstrates the use of high resolution work for heterointerface and related investigations in two different areas.The epitaxial growth of wide band gap II-VI compounds offers potential for a number of optoelectronic device applications. Indeed, in some cases, such as for CdS, it is possible to prepare very high quality Wurtzite-structure layers on Sphalerite substrates, despite the presence of substantial misfit. When hexagonal close-packed CdS is grown by metal-organic chemical vapour deposition on (111)A GaAs, the layer is oriented with (0001)cds //(111)GaAs and [110]cds//[10]GaAs. A cross-sectional, high resolution micrograph of the interface is shown in Fig. 1a where the different atomic stacking in the CdS (ABAB....) and GaAs (ABCABC....) regions is evident.
Structural aspects of silicon diffusion in quaternary III-V thin-film semiconductors
Authors: Ponce F. A. , Thornton R. L. , Anderson G. B. 
Published: June 2020

The InGaAlP quaternary system allows the production of semiconductor lasers emitting light in the visible range of the spectrum. Recent advances in the visible semiconductor diode laser art have established the viability of diode structures with emission wavelengths comparable to the He-Ne gas laser. There has been much interest in the growth of wide bandgap quaternary thin films on GaAs, a substrate most commonly used in optoelectronic applications. There is particular interest in compositions which are lattice matched to GaAs, thus avoiding misfit dislocations which can be detrimental to the lifetime of these materials. As observed in Figure 1, the (AlxGa1-x)0.5In0.5P system has a very close lattice match to GaAs and is favored for these applications.In this work, we have studied the effect of silicon diffusion in GaAs/InGaAlP structures. Silicon diffusion in III-V semiconductor alloys has been found to have an disordering effect which is associated with removal of fine structures introduced during growth. Due to the variety of species available for interdiffusion, the disordering effect of silicon can have severe consequences on the lattice match at GaAs/InGaAlP interfaces.
TEM in situ annealing of fluorine-implanted amorphized silicon
Authors: Kaushik Vidya S. , Hance Robert L. , Grove Charlotte L. 
Published: June 2020

In situ heating experiments in the transmission electron microscope offer unique opportunities to visualize and understand material behavior. The annealing behavior of silicon amorphized by conventional dopant implants as studied by in situ TEM has been reported in the literature. As part of a study on the behavior of fluorine in silicon, we have performed in situ anneals of fluorine-implanted amorphized silicon on XTEM samples, and compared these with bulk furnace-annealed samples.The wafer was an n-type (100) silicon (18-24 ohm-cm) implanted with 1 x 1016 /cm2 fluorine at 60 keV at room temperature through a 13 nm oxide layer. The XTEM samples were heated within the TEM in a Gatan sample holder in a JEOL 2000 FXII STEM operated at 200 kV. The behavior of the sample was observed using a wide angle CCD TV camera and recorded on videotape. Micrographs were recorded before the anneal and after the temperature had stabilized.