bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopy study of shock synthesis of silicides
Authors: Vecchio Kenneth S.
Published: June 2020

Shock-induced reactions (or shock synthesis) have been studied since the 1960’s but are still poorly understood, partly due to the fact that the reaction kinetics are very fast making experimental analysis of the reaction difficult. Shock synthesis is closely related to combustion synthesis, and occurs in the same systems that undergo exothermic gasless combustion reactions. The thermite reaction (Fe2O3 + 2Al -> 2Fe + Al2O3) is prototypical of this class of reactions. The effects of shock-wave passage through porous (powder) materials are complex, because intense and non-uniform plastic deformation is coupled with the shock-wave effects. Thus, the particle interiors experience primarily the effects of shock waves, while the surfaces undergo intense plastic deformation which can often result in interfacial melting. Shock synthesis of compounds from powders is triggered by the extraordinarily high energy deposition rate at the surfaces of the powders, forcing them in close contact, activating them by introducing defects, and heating them close to or even above their melting temperatures.
EM study of carbon content effects on carbide precipitation and chromium depletion in type 304 stainless steels
Authors: Trillo E.A. , Advani A.H. , Murr L.E. , Fisher W.W.
Published: June 2020

Carbon content is the most critical compositional variable in carbide precipitation and sensitization development in stainless steels (SS). Quantitative electrochemical test methods have conclusively demonstrated that an increase in carbon content enhances the susceptibility of SS to sensitization development. The increase in sensitization has been considered to be caused by the influence of carbon on the thermodynamics of the precipitation-depletion process. This has been supported by limited TEM work. In this research, we are using electron microscopy to quantify the effects of carbon content on carbide precipitation and chromium-depletion development in SS. Initial observations that compare precipitation characteristics and depletion profiles in 0.011% C, 0.025% C, 0.051% C, and 0.07% C-containing, 304 SS heat treated at 775°C for 0.1-500 h are presented in this paper, and will be enhanced by a statistical analysis of carbon content effects on precipitate sizes, densities, and depletion profiles, to provide a valuable insight into the precipitation-depletion phenomena.
TEM study on the thermostability of hafnium carbide dispersoids in tungsten at ultrahigh temperatures
Authors: Liu Mingqi , Cowley John M.
Published: June 2020

Tungsten dispersed by hafnium carbide (HfC) particles has been found to be the strongest metallic material at temperatures above 2000 K. The strength of W-HfC alloy is directly related to the thermostability of HfC particles at ultrahigh temperatures. In the present study, the growth behavior and growth mechanism of HfC particles from 2200 to 3000 K are examined with transmission electron microscopy (TEM) and a correlation between the particle size and alloy strength is established.

The examined material was a tungsten-3.6 wt%rhenium-0.35 wt%HfC alloy. The solid solution element rhenium was to improve the fabricability of tungsten at room temperature. Specimens were heated to a temperature between 2200 and 3000 K for two hours and then deformed in tension. After a 5% elongation, the specimens were rapidly cooled down to room temperature at a cooling rate greater than 200 K/s in order to maintain the high temperature substructures which were examined with a JEM-2000FX high resolution TEM.
EELS and stopping-power calculation of the superconductor Bi1.8Pb0.3Sr2Ca2Cu3O10
Authors: Dunlap J. R. , Luo S. , Joy D. C. , Chakoumakos D. C. , Zhu S. , Sun Y.
Published: June 2020

Several studies have been undertaken to investigate the fine structure and superconductive properties of high temperature superconductors. Yuan et al. utilized electron energy loss spectroscopy (EELS) to determine the dielectric function of the superconductor Ba2YCu3O7-x. In this study we performed EELS on the superconductor Bi1.8Pb0.3Sr2Ca2Cu3O10at both room temperature and below the transition temperature and calculated such properties as the dielectric fuction, the inelastic mean free path and the stopping power for this material.

Powdered Bi1.8Pb0.3Sr2Ca2Cu3O10was dispersed by sonication in a 0.2% (wt/v) solution of poly-(N-vinylpyrrolidone) in isoproponal. Individual crystals were allowed to settle and dry on a lacey cabon film. Figure 1 shows a typical individual crystal and Fig.2 shows a typical diffraction pattern. Electron energy loss spectra were recorded from single crystals which extended into holes in the film. The EEL spectra were recorded at room temperature and at 95°K which is below the transition temperature of 105 °K.
High resolution Scanning Electron Microscopy
Authors: Joy David C.
Published: June 2020

High resolution scanning electron microscopy is still a relatively new and unfamiliar concept because in the early days of the SEM it was expected, that secondary electron imaging would be limited to a resolution of between 5 and 10nm at best. Now, however, because of improvements in instrumentation and technique based on advances in the understanding of electron beam interactions with solids current SEMs can demonstrate spatial resolutions below 1nm, rivaling those obtained by transmission instruments.

High performance scanning electron microscopes always incorporate two advanced items of instrumentation. Firstly they use field emission guns (FEGs). The high brightness, low energy spread, and small source size of the FEG makes it possible to produce an electron probe of sub-nanometer size which contains sufficient current for secondary electron imaging (i.e 10-12 amps or more) and which can maintain this performance over a wide energy range (3 to 30keV). Secondly, the new high performance instruments place the specimen within a high excitation, immersion, probe forming lens.
Practical applications of scanning tunneling microscopy
Authors: Denley D. R.
Published: June 2020

Scanning tunneling microscopy (STM) has recently been introduced as a promising tool for analyzing surface atomic structure. We have used STM for its extremely high resolution (especially the direction normal to surfaces) and its ability for imaging in ambient atmosphere. We have examined surfaces of metals, semiconductors, and molecules deposited on these materials to achieve atomic resolution in favorable cases.

When the high resolution capability is coupled with digital data acquisition, it is simple to get quantitative information on surface texture. This is illustrated for the measurement of surface roughness of evaporated gold films as a function of deposition temperature and annealing time in Figure 1. These results show a clear trend for which the roughness, as well as the experimental deviance of the roughness is found to be minimal for evaporation at 300°C. It is also possible to contrast different measures of roughness.
Scanning tunneling microscopy (STM) of DNA and RNA
Authors: Arscott Patricia G. , Lee Gil , Bloomfield Victor A. , Evans D. Fennell
Published: June 2020

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.

We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).
Application-driven computerisation of the energy filtering Electron Microscope for imaging and analysis
Authors: Bauer R. , Probst W. , Lamprecht G.
Published: June 2020

An Energy Filtering Electron Microscope (EFEM) with an integrated imaging energy loss spectrometer offers many different methodes for imaging and analysis. Thus there is a wealth of different information from a specimen. They are all related to the structure as well as to the physical and chemical composition of a specimen. There are e.g. geometrical and statistical information from brightfield and darkfield images, information about crystalline structures from diffraction images, chemical information from electron energy loss spectra and highly resolved elemental distribution images. Most of this information is detail information not final results. To get final results, detail information have to be related and processed. To do this reliably and economically it is important to have a powerful and flexible computer system permanently available on the microscope to record, enhance, process, evalute, analyse, and store images, spectra and data. An important point is the use of the computer capabilities to perform automatic control of the microscope.
Computer controlled TEM
Authors: Kersker M. , Lehman J. , Rowlands N.
Published: June 2020

The use of the microprocessor and/or computer for the control of lenses, deflectors, stigmators, camera, gun, accelerating voltage, vacuum system, etc. in the transmission microscope has resulted in improved and simplified operation of the microscope without a consequent sacrifice in the operating flexibility of the TEM. Based on years of experience with electron microscopists, the basic ergonometric design of the microprocessor/computer controlled instrument remains unchanged since the microscopist still has to stradle the microscope in order to operate the stage and apertures. Potentiometers are replaced by rotary encoders, programming of the encoders and of the entire instrument is accomplished by factory upgradable PROMs, and function switches have been added that are uniquely programmable and hence upgradable. Operating simplicity and improved performance were a consequence of the major design consideration, “keep the microscope properly aligned.”

Under properly aligned conditions an operator can then easily operate in STEM mode, normal TEM imaging mode, diffraction mode, low mag mode.
In environmental Scanning Electron Microscopy, the secondary electron signal reveals surface information not accessible by conventional backscattered electron signals
Authors: Peters Klaus-Ruediger
Published: June 2020

Environmental scanning electron microscopes (ESEM) operate at high as well as at low vacuum (<2.5 kPa: ~20 Torr) but utilize all advantages of conventional high vacuum SEM (large specimen size, high depth of focus and specimen tilt capability, TV-rate scanning for imaging dynamic events). They have the advantage of imaging wet specimens as well as insulators without the need of any specimen preparation. Previously, environmental scanning microscopy was restricted to the BSE signal collected with BSE detectors. SE signals cannot be collected with the Everhart-Thornley detector because it cannot operate at low vacuum. Using positively biased electron collectors, it is now possible to collect an SE signal. However, the origin and quality of this signal need to be further characterized.

An ElectroScan ESEM was used equipped with SE and BSE detectors and operated at 7-30 kV with partial water pressures of 0.1-2.5 kPa (∼1-20 Torr).
Low-voltage high-resolution Scanning Electron Microscopy of semiconductors
Authors: Krause S.J. , Maracas G.N. , Varhue W.J. , Joy D.C.
Published: June 2020

The advent of scanning electron microscopes (SEMs) with reliable, high performance field emission guns (FEG) has afforded many opportunities to obtain new information at low voltages not available at higher voltages in traditional SEMs equipped with tungsten hairpin or LaB6 filaments. The FEG SEMs are able to operate at low voltages with both high brightness and high resolution (HR) due to the small source size and low energy spread of the beam. Resolution of 4 nm down to 1.5 nm are routinely possible in the energy range from 1 to 5 keV along with standard image recording times of 1 to 2 minutes. The low voltage capabilities have allowed insulating materials, such as polymers, composites, and ceramics to be imaged at high resolutions at energies below the second crossover, usually around 1 to 2 keV, without experiencing image artifacts from negative surface charging normally found in uncoated insulators at higher operating voltages.
Secondary electron imaging of MoO3 reduction in a UHV STEM
Authors: Crozier P. A. , Liu J. , Cowley J. M.
Published: June 2020

Recently, a number of people have studied the ability of focussed electron beams to form lines and holes in metal oxides. Many metal oxides decompose when irradiated under the high intensity focussed probes used in field emission STEMS. Initially, many of these oxides reduce to the metal and in some cases it is possible to drill holes in the material. Understanding the nature of the interaction between the electron beam and the sample is important for materials characterisation. These studies may also lead to the development of new electron beam resists and masks. Here we present some preliminary results on the effect of electron irradiation on MoO3 in a field emission UHV STEM. We show, for the first time, secondary electron (SE)images of the entrance and exit surface of the sample after radiation damage has occurred.

The experiments described here were performed on the VG HB501S; a dedicated STEM in which vacuums better than 10-10 torr are routinely available in the column.
Design of a TEM/STEM Auger Detector
Authors: Ai R.
Published: June 2020

In order to perform surface studies in an electron microscope, one has to be able to detect atoms adsorbed on the surface. The standard approach in surface science is to attach an Auger spectrometer using a CMA or CHA, but such an instrument is intrinsically incompatible with the performance of a TEM/STEM. In this note we describe a design which uses a far smaller analyzer which should be compatible with almost all microscopes.

One important aspect of the design is to recognize that due to the strong magnetic lenses, low energy electrons are refocussed along the optic axis of the microscope, based on our trajectory calculations. As an example, Figure 1 shows the calculated trajectories for 500 eV electrons through the upper pole piece of the UHV-H9000 microscope. Figure 2 shows a graph of the final focus position as a function of energy, from which it is apparent that for most energies a final focus occurs between 5mm to 9mm from the specimen;
Field-emission gun and illuminating lens system for 200kV FE-TEM
Authors: Murakoshi H. , Ichihashi M. , Komoda T. , Isakozawa S. , Kubo T.
Published: June 2020

Good resolution is obtained with a conventional transmission electron microscope (TEM). Nevertheles, an atomic scale analysis is difficult because of insufficient probe current. A field emission gun (FEG) provides a higher brightness and more monochromatic beam than a thermionic one. Thus, an FEG can be expected to improve the abilities of a TEM. The low energy spread(∼0.5 eV) attainable with the FEG reduces chromatic aberrations and a brighter image can be expected, making more discernible details. In addition, a high beam current is formed in a small spot, enabling precise element analysis at the nanometer level. Moreover, the illuminating angle obtained on a specimen is so small that electron diffraction can be clearly obtained for structure analysis of crystals. Experimental FE-TEMs with lower accelerating voltage than 100kV have already been developed. Using an electron holography technique, micro magnetic flux was observed with a high coherency beam. FE-TEMs with a higher accelerating voltage are required in various fields of material science.
High-voltage Electron Microscopy and 3-D reconstruction of human hair fiber ultrastructure
Authors: Rudy L. , Sneath R. , Song M.
Published: June 2020

The basic morphology of the non-keratinous regions of human hair fibers was studied using both conventional and high voltage electron microscopy. The non-keratinous regions of hair include the endocuticle, the cell membrane complex, and the nuclear remnants of the cortex. By characterizing these regions more clearly, the mechanisms by which external influences affect the hair can be understood. The nuclear remnants are surrounded by a cell membrane complex. Since thin sectioning often causes artifacts in these fragile structures, a three-dimensional reconstruction using serial, semi-thick sections was completed to reveal their morphological nature.

Human hair fibers collected from a female subject, had not been treated with any chemically active processes. One centimeter samples were collected near the scalp region of the back of the head. The fibers were embedded in Epon-812. Serial, semi-thick sections, 0.25u thick, were sectioned and collected on copper slot, formvar-coated grids. Post-staining was completed with uranyl acetate and lead citrate. Sections were examined in an AEl EM7 Mk 1.2MV HVEM at an accelerating voltage of 1.0 MV.
Real-time confocal imaging ofStentor coeruleusin epi-reflective mode by using a Tracor Northern tandem scanning microscope
Authors: Chen V. K-H. , Cheng P. C.
Published: June 2020

Confocal microscopes with a spinning disk design are potentially useful in the study of dynamic processes in biological systems. However, the image brightness of the spinning disk type confocal microscope is generally quite low.

A Tracor Northern Tandem Scanning confocal microscope (TSM) modified to accept a TV camera-coupled second generation image intensifier was used in this study. An Olympus 38mm Macro lens (f/2.8) was used in place of the original eyepiece to relay the image of the spinning disk onto the photocathod of the image intensifier. In order to fit the macro lens and the image intensifier onto the microscope, a set of adaptors were designed and fabricated. Figure 1 shows the microscope set-ups. To increase the image intensity, a 200W Mercury short arc lamp was used as the light source. An UV filter was used to remove radiations harmful for living specimen.
Microstructure of YBa2Cu3O7-x thin films deposited by dc sputtering
Authors: Eibl O. , Gieres G. , Behner H.
Published: June 2020

The microstructure of high-Tc YBa2Cu3O7-X thin films deposited by DC-sputtering on SrTiO3 substrates was analysed by TEM. Films were either (i) deposited in the amorphous state at substrate temperatures < 450°C and crystallised by a heat treatment at 900°C (process 1) or (ii) deposited at around 740°C in the crystalline state (process 2). Cross sections were prepared for TEM analyses and are especially useful for studying film substrate interdiffusion (fig.1). Films deposited in process 1 were polycristalline and the grain size was approximately 200 nm. Films were porous and the size of voids was approximately 100 nm. Between the SrTiO3 substrate and the YBa2Cu3Ox film a densly grown crystalline intermediate layer approximately 150 nm thick covered the SrTiO3 substrate. EDX microanalyses showed that the layer consisted of Sr, Ba and Ti, however, did not contain Y and Cu. Crystallites of the layer were carefully tilted in the microscope and diffraction patterns were obtained in five different poles for every crystallite. These patterns were consistent with the phase (Ba1-XSrx)2TiO4. The intermediate layer was most likely formed during the annealing at 900°C. Its formation can be understood as a diffusion of Ba from the amorphously deposited film into the substrate and diffusion of Sr from the substrate into the film. Between the intermediate layer and the surface of the film the film consisted of YBa2Cu3O7-x grains. Films prepared in process 1 had Tc(R=0) close to 90 K, however, critical currents were as low as jc = 104A/cm2 at 77 K.
Microstructure of highly dense Ba2YCu3O7-δ superconductive materials
Authors: Park K. , Yamamoto T. , Green M. , Hasegawa T. , Kishio K. , Kitazawa K. , Fueki K.
Published: June 2020

Since the breakthrough discoveries by Bednorz and Muller and Wu et al., superconductivity in Cu-O based ceramic materials has been the subject of tremendous research and development interest. In particular, the Ba2YCu3O7-δ type oxide is very important from a practical point of view, since it has a superconducting transition temperature (Tc) around 90K, which is above the liq. N2 boiling temperature.
HREM studies of YBa2Cu3O7-δ prepared from low-temperature precursors
Authors: Dufner D.C. , Ram R.A. Mohan , Clearfield A.
Published: June 2020

Solid state reactions are the most commonly employed processes for the preparation of high-Tc superconducting ceramic oxides. However, there has been considerable effort expended to prepare the YBa2Cu3O7-δ (1-2-3) superconductor by low-temperature solution methods in order to obtain a more homogeneous oxide mixture resulting in products with superior superconducting properties. Proper processing of the precursors resulting in less preparation time, lower temperature of firing, higher critical current density, higher flux expulsion, etc., is expected.

Our laboratory has been preparing low-temperature precursors by sol-gel and other methods. We employed the same methods for the preparation of 1-2-3 superconductors. The precursors were heated at 925°C for 12 hours in flowing oxygen. The resulting powder was found to be superconducting at 92.3K. Superconducting properties were measured by resistivity and impedance measurements.
The future of AEM: Toward atom analysis
Authors: Cliff G. , Kenway P.B.
Published: June 2020

The ultimate goal of analytical electron microscopy (AEM) is a minimum detection limit, MDL, of one atom! Utilising the small probes and the high current densities attainable using a field emission gun, FEG, in a scanning transmission electron microscope, STEM, the MDL is at present 100 atoms. This discussion will show that an MDL of 1 atom could be achieved with existing engineering technology available on the current generation of AEM instrumentation.Indeed if AEM was like hi-fi an AEM analyst could today combine features of different microscopes to build an AEM capable of atom detection!

The parameters affecting the MDL include a) the electron source brightness, b) the detector solid angle, c) the operating voltage and, less frequently discussed, d) the Cs of the probe-forming lens.

a) Electron source brightness. The highest brightness electron source is the FEG as used in the dedicated STEM which achieved the MDL quoted above. This is the only source capable of producing the high current density in a small probe required to reduce the MDL to atomic proportions.
The Z band in skeletal muscle in rigor exhibits the activated lattice form
Authors: Edwards R. J.
Published: June 2020

The Z band of skeletal muscle is a tetragonal array of interdigitating thin filaments from adjacent sarcomeres held together by cross connecting filaments. Two visually unique forms of the Z band (small square, ss, and basketweave, bw) can be observed by TEM of cross sections. The ss form is found in relaxed muscle and the bw is found in maximally activated muscle. The average Z spacing in the bw form is 20% largerthan in the ss form. There is a correlation between active tension and the form of the Z band. This correlation suggests that cross bridge binding in the A band is directly related to the form of the Z band. In rigor, the cross bridges are completely bound; therefore, we predicted that the Z band would exhibit the bw form. To test this hypothesis we compared unstimulated muscle to glycerinated muscle in rigor.
Microstructural determination of a metastable phase during rhodium oxidation
Authors: Logan A. David
Published: June 2020

In heterogeneous catalysis, oxidation of the catalyst is frequently used as a means of removing impurities from the active surface. However, bulk oxidation severely alters the microstructure of the metal due to atom repositioning and valence changes. Transformation of Rh to Rh2O3causes the lattice structure to change from fcc to hexagonal with a resulting volume expansion of 90% due to density changes. This is the reported cause for fracturing of crystallites and variations in reactivity. In this study, microstructural changes during progressive oxidation of 5 nm metal Rh particles have been examined.

A 2 wt% Rh/Silica catalyst was prepared using Rh(III)-2,4 pentanedionate as a precursor and nonporous silica spheres as a support. The catalyst was then reduced in flowing H2at 473 K. High resolution electron microscopy (HREM) was performed on a JEM-4000EX having a point resolution of 0.17 nm. The catalyst was oxidized in research purity O2(Matheson 99.99%) using an all glass volumetric chemisorption system.
Characterization of second-phase particles in NiAl-containing trace additions of Zr
Authors: Locci I. E. , Noebe R. D.
Published: June 2020

X-ray microanalysis and electron diffraction were used to characterize the second phase particles observed in Zr-doped single crystal and polycrystalline NiAl. Zirconium is the most common addition made to NiAl because of its positive effect on the cyclic oxidation behavior of this intermetallic. While the effect of Zr on the oxidation behavior of polycrystalline and single crystal NiAl has been studied in detail, the effect of Zr on the microstructure and mechanical behavior of NiAl has generally been ignored.

An intermetallic phase, rich in Zr and Si, was observed in directionally solidified NiAl single crystals. Figure 1 is a dark field and bright field image ofthese precipitates. Diffraction analysis indicated that the second phase was a nickel zirconium silicide (Ni16Zr6Si7). This phase was observed in crystals obtained from two separate sources. All crystals were near stoichiometry in composition and contained 0.1 wt.% Zr as well as an unintentional addition of 0.07-0.10 wt.% Si. Silicon contamination was probably the result of reaction between the NiAl melt and the crucible. The precipitates ranged in size from 10 to 40 nm. Occasionally, strings of precipitates were observed in dislocation paths, suggesting preferential nucleation induced by the presence of crystal defects. Figure 2 illustrates the cuboidal shape of the precipitates as observed near an [011] zone axis; two faces of the cube can be distinguished.
Electron spectroscopic imaging (ESI) on multiphase polymer materials
Authors: Cantow H.-J. , Kunz M. , Möller M.
Published: June 2020

In transmission electron microscopy the natural contrast of polymers is very low. Thus the contrast has to be enhanced by staining with heavy metals. The resolution is limited by the size of the staining particles and by the fact that electrons with different energy are focused in different image planes due to the chromatic aberration of the magnetic lenses. The integration of an electron energy loss spectrometer into the optical coloumn of a transmission electron microscope offers the possibility to use monoenergetic electrons and to select electrons with a certain energy for imaging. Thus contrast and resolution are enhanced. By imaging only electrons with an element specific energy loss the element distribution in the sample can be obtained. In addition, elastic bright field images and diffraction patterns yield excellent resolution. Some applications of the method on multicomponent polymer materials are discussed.

Bulk polymer samples were prepared by ultramicrotoming at room temperature or well below the glass transition temperature. Very thin films for the direct observation of the structure in semicrystalline polymers were obtained by melt-spinning. Specimens were examined with a ZEISS CEM 902 operated at 80 kV.
Characterization of high-performance polymer blends
Authors: Chen R.T. , Rafalko J.J. , Sawyer L.C.
Published: June 2020

Blending of polymers, a method used to engineer materials to provide specific properties, has been extended to high performance materials being developed for composite applications in the aerospace industry. The high performance requirements of such blends demand a complete understanding of the chemistry and morphology as a function of end-use temperatures. Multidisciplinary protocols for characterization of blends include microscopy, infrared and thermal analysis. The major issues involved in such a study of polymer blends will be described.

Recently the Hoechst Celanese polybenzimidazole, [poly-2,2′(m-phenylene)-5,5′ bibenzimidazole], PBI, and the General Electric aromatic polyether imide [poly(2,2′-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane-m-phenylenediimine], Ultem 1000, which are being evaluated for aerospace applications, were found to form miscible blends. The large parts are being fabricated from fibers spun from concentrated solutions (dopes).
The crystalline modifications and the morphology and structure of J-1 polymer spherulites
Authors: Li L. S. , Geil P. H.
Published: June 2020

The J-1 polymer (Poly(bis 4, 4' dicyclohexylmethane)n-dodecanediamide) (E. I. du Pont)

has a well defined chain structure in which cyclohexyl groups and intermolecular hydrogen bonds make the chains rigid. This results in a high melting point for this polymer in the range of 290°C. However, there is also some flexibility in the chains of this polymer due to the -(CH2)10- segments and -(CH2)- groups between every two cyclohexyl groups along the chains. The combination of rigidity and flexibility in the J-1 polymer would lead to a variety of morphologies. In order to varify this we have studied the morphology and structure of the J-1 polymer crystallized from solution.

Thin films of J-1 polymer with single crystals and six different kinds of spherulites were prepared by evaporation of solvent from am-cresol solution of J-1 polymer at temperatures of 160°-210°C. The thin films were examined in both polarizing and electron microscopes. A Philips 430 electron microscope was used at 200, 250 or 300 kV accelerating voltages.
Schottky barrier measurement by electron energy loss spectroscopy
Authors: Batson P.E.
Published: June 2020

It is difficult to imagine an electrical property which is more crucial to the success of modern device structures than the Schottky Barrier. In spite of this, the mechanism of barrier formation is still imperfectly understood, because the barrier formation is essentially a result of the details of the micro-structure of the metal/semiconductor interface. High resolution microscopy can obtain the microstructure of small regions of interfaces, but typical tools for measuring electronic structure have been able to measure only the bulk, or average, properties. Recently, scanning tunneling microscopy, using ballistically injected electrons, was used to obtain I-V characteristic of a buried junction. It was possible to image the junction in the plan-view geometry to show how the junction electrical properties change on a scale of 1 nm. These studies showed barrier changes with morphology and promise to provide useful insight into the problem. However, the studies do not obtain electrical properties as a function of distance away from the junction. This information is needed to help understand the underlying physics of the barrier formation. Thus, there is a need for an analytical tool which is compatible with the high resolution TEM imaging of interfaces in the cross-section geometry. Electron energy loss scattering can provide this tool if a small probe and a high energy resolution can be obtained.
Integrated morphometrical and electron energy loss image analysis in cytochemistry
Authors: de Bruijn W.C. , de Jong A.A.W. , Sorber C.W.J.
Published: June 2020

One aspect of enzyme cytochemistry is, whether all macrophage lysosomal hydrolytical enzymes are present in an active form, or are activated upon stimulation. Integrated morphometrical and chemical analysis has been chosen as a tool to illucidate that cytochemical problem. Mouse peritoneal resident macrophages have been used as a model for this complicated integration of morphometrical and element-related data. Only aldehyde-fixed cells were treated with three cytochemical reactions to detect different enzyme activities within one cell (for details see [1,2]). The enzyme-related precipitates anticipated to be differentiated, were:

(1).

lysosomal barium and sulphur from aryl sulphatase activity,

(2).

lysosomal cerium and phosphate from acid phosphatase activity and

(3).

platinum/di-amino-benzidine( D A B) complex from endogenous peroxidase activity.
A 2-dimensional detection system for Electron Energy Loss Spectroscopy
Authors: von Harrach H.S. , Colling J.A.
Published: June 2020

A UHV-compatible parallel and serial detection system for electron energy-loss spectroscopy (EELS) has been developed for the VG HB501 field-emission scanning transmission electron microscope (STEM) using a 2-dimensional detector. As pointed out previously the charge coupled devices (CCD) available commercially are vastly superior, in terms of read-out noise, to linear photodiode arrays which are currently used for parallel EELS detection. This feature, together with the ability of operating as an imaging and storage device, makes the 2-dimensional CCD array an attractive choice for parallel EELS and low light-level imaging applications.

The system reported here (Fig. 1) is an extension of the VG ELS501 sector magnetspectrometer used for serial EELS with many STEMS. It uses one quadrupole lens to magnify the energy-loss spectrum over a range of 2 to 0.1 eV per detector element. An electromagnetic deflector steers the spectrum to one of three YAG scintillators. Two of these scintillators with suitable masks are used for parallel EELS detection; the third is used for serial EELS and energy filtered STEM imaging via a lightguide and photomultiplier system by scanning the beam across a variable slit as in ELS 501 systems.
Reactions at metal-semiconductor interfaces
Authors: Sinclair Robert
Published: June 2020

Examination of the architecture of a semiconductor-based microelectronics device shows that metallic, highly conductive components are an integral part of the miniature circuits. As geometries become increasingly small (e.g. at the sub-micron level) the structure at critical interfaces influences the electrical performance to a greater extent. Accordingly metal-semiconductor junctions have significant technological importance, in addition to any natural scientific interest associated with the bonding of two unlike materials. This article reviews some of our recent work on this topic, with particular emphasis on the reactions which can occur either during fabrication of the interface or upon heating in conjunction with device processing or prolonged service.

The simplest system consists of an elemental metal and an elemental semiconductor, silicon being the most important example of the latter. Consideration of phase equilibria indicates that such an interface is thermodynamically unstable: upon heating either a reaction can occur to produce a compound phase (i.e. a silicide), or mutual dissolution of the elements within each other takes place to achieve saturated solid solution compositions. Reference to the appropriate binary phase diagram allows prediction of the result if local equilibrium is achieved. Thus although an atomically abrupt metal-semiconductor interface might be grown under specialized circumstances, this situation can be expected to be unusual and moreover it is not stable to elevated temperatures when atomic mobility and diffusion are rapid.
Studies of CoSi2 nano-structures produced by high-dose ion implantation in Si
Authors: Berger S.D. , Loretto D. , Huggins H.A. , White Alice E. , Short K.T. , Bahnck D.
Published: June 2020

Recently it has been shown that buried layers of single crystal, orientated CoSi2 Can be produced in silicon by implanting high doses of Co followed by a high temperature anneal. This process is known as mesotaxy. The original implant produces a skewed Gaussian distribution of ions. However, on annealing it is found that the distribution sharpens dramatically to give layers which nave flat and abrupt interfaces and are of very good structural and electrical quality.

Using a combination of electron beam lithography and reactive ion etching we have fabricated masks which confine the implant dose laterally. In this way we are able to produce discrete structures of CoSi2 with nanometer dimensions. Furthermore, we can now investigate the epitaxial growth process which occurs during the anneal by varying the structure's dimensions, shape and crystallographic orientation with respect to the substrate.
Epitaxial films of CoSi2 on Si (311) and Si (211)
Authors: Batstone J.L. , Phillips Julia M.
Published: June 2020

Cobalt silicides can be grown epitaxially on silicon by room temperature (RT) deposition of Co onto in-situ cleaned Si in an ultra high vacuum environment. Post-deposition annealing at ∼550°C leads to the formation of CoSi2 which exists in two orientations on Si (111), known as type A and type B. The fractional coverage of type A CoSi2 is critically dependent on the metal thickness. If <10Å Co is deposited at RT, type B CoSi2 is formed. For >10Å Co, intermediate metal-rich silicide phases such as Co2Si and CoSi are formed at low (<450°C) temperatures. At >500°C, mixed A+B type CoSi2 is formed. If higher reaction temperatures are employed, large (∼2000Å) pinholes open up allowing dislocation motion and a conversion of the film to entirely type B CoSi2.

Epitaxial growth of CoSi2 on Si (311) has recently been demonstrated. Two orientations, A and B were observed where the B orientation was rotated with respect to the substrate about the inclined (111) axis. Electrically continuous films were obtained at temperatures as low as 500°c with residual resistivities ∽10μΩcm. This work has now been extended to study the effects of substrate orientation on intermediate phase formation in the Co/Si system.
Analysis of transition metal induced surface defects in silicon following apid thermal processing
Authors: Kola R.
Published: June 2020

Rapid Thermal Processing(RTP) is extensively used in VLSI technology for implant activation, licidation, oxidation, and passivation glass reflow. The diffusion of back-side depositions of transition metals during rapid thermal annealing and the resulting front-side defect formation in silicon has recently been investigated by several authors but a detailed analysis of the defect structure, morphology, and chemistry is lacking. The defect structure and chemistry on both the front and back sides of the wafers ter RTA were investigated by TEM on plan-view and cross-section foils. A Philips EM430 microscope ierating at 300 KeV and a Hitachi H-800 microscope operating at 200 KeV were used. Ni and Cu sputter deposited on the back-side of 4 inch diameter (100) Si wafers were diffused for 10 sec at 1150°C in trogen ambient. The thickness of the metal film was 50 nm. A Heatpulse 2101 RTA system was used.

Fig. 1 is a CDF micrograph showing a group of precipitates on the front surface of a sample nickel diffused from the back surface.
Centrosymmetric and nonsymmorphic aluminum oxynitride spinel
Authors: Dravid V. P. , Sutliff J. A. , Weslwood A. D. , Nolts M. R. , Lyman C. E.
Published: June 2020

There is considerable controversy concerning the point and space group of crystals based on the spinel structure. The debated question is whether the space group of spinel crystals is or . has noncentrosymmetric point group and is symmorphic; has centrosymmetric point group and is nonsymmorphic. One characteristic of the space group that distinguishes it from is that reflections hkl such that h+k, k+l, h+l ≠ 4n, for example {200}, are kinematically forbidden.

MgAl2O4 spinel was studied by Steeds and Evans whose observations of {200} reflections in {001} ZAPs lead them to conclude that the space group of this crystal was . de Coomen and Carter also investigated MgAl2O4 spinel and came to the same conclusion. Although these authors do emphasize the importance of a HOLZ contribution to double diffraction, they do not show the effect of changes in accelerating voltage on the HOLZ segment responsible for double diffraction. To clearly show that {200} reflections appear only as a result of double diffraction via HOLZ, it is essential to observe both the {200} reflections and the HOLZ segment as a function of accelerating voltage.
CBED from imperfect crystals: Current achievements and future prospects
Authors: Cherns D. , Jordan I.K.
Published: June 2020

CBED is usually applied to the study of perfect crystals. However, we have recently shown that CBED can be usefully applied to the study of a range of individual defects (dislocations and stacking faults) and to the study of composition profiles in a range of periodic and aperiodic semiconductor multilayers. In this paper the advantages of CBED for such studies over conventional imaging techniques will be explained and the scope for future work discussed.

The application of CBED to the study of dislocations has already been discussed in a series of papers. The technique is to use the large angle method (LACBED) such that a shadow image of a given dislocation is seen in diffraction. The interaction with diffraction contours can then be studied as a function both of deviation parameter and distance from the dislocation core (fig 1). Since in CBED or LACBED we can identify diffraction into higher order reflections than is normally possible in imaging (for example the higher order Laue zone deficiency lines in fig 1), large g.b values are possible with corresponding high sensitivity to the dislocation strain field. One application has been to examine small Burgers vectors, such as those associated with stair-rod dislocations. A further advantage is that, for large g-vectors, image contrast can be explained qualitatively by a simple kinematical model giving the magnitude of the Burgers vector from the number of subsidiary peaks into which the diffraction contour splits. The sign of the Burgers vector follows from the image asymmetry.
Observation of surface morphology by reflection electron holography
Authors: Osakabe N. , Endo J. , Matsuda T. , Tonomura A.
Published: June 2020

Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.

The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.
SEM and x-ray EDS studies on the adhesion of novel bisoxazoline-phenolic copolymers to carbon and glass fibers, and metallic filler surfaces
Authors: Deviney M.L. , Brostrom L.R. , Menardi P.J. , Culbertson B.M. , Tiba O.
Published: June 2020

A very promising new entry into the family of polymers for advanced composites, for aerospace and heavy duty industrial applications requiring high service temperature and/or low flammability, are bisoxazoline-phenolic resins derived from the step-growth copolymerization of 1,3 (or 1,4)-phenylene bisoxazoline (PBOX) and phenol-free phenolic resins. This new resin system offers a very attractive group of properties, including high modulus, high compressive and shear strengths, excellent toughness, high heat distortion temperature, no volatiles evolution and low shrinkage (<1%) during cure, low flammability and low smoke production, good electrical properties, relatively low coefficient of thermal expansion, very good thermal shock resistance and machinability, and excellent adhesion to carbon fibers, fiberglass and powdered (5 to 20 μm) metal fillers (e.g., iron and aluminum).

In this paper are presented example scanning electron microscopy (SEM) micrographs of PBOX-phenolic interfacial regions with both reinforcing fibers and metallic fillers. Carbon fiber reinforced composite specimens were examined by SEM (CamScan Series 4 instrument) after testing to failure using standard ASTM shear, flex and compression tests.
Transmission electron microscopy and high resolution scanning electron microscopy of Co-Ni-Pt thin film magnetic recording media
Authors: Chan L. , Yamashita T. , Sinclair R.
Published: June 2020

In thin film magnetic media, the magnetic hysteresis properties and micromagnetic domain behavior are strongly influenced by both interparticle exchange interactions and by magnetostatic interactions. The exchange interactions are short-range in nature; therefore, they are very sensitive to interparticle separation. Consequently, the magnetic hysteresis properties and the recording behavior of the thin film magnetic media can be drastically altered by the introduction of grain separation during the film deposition process. In this study, thin film media of a CoNiPt alloy of one composition was processed under two different conditions. Transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HRSEM) were used to investigate and explain the difference in magnetic hysteresis characteristics of the films.

The structure of the thin film media consisted of a 600 Å thick CoNiPt alloy sputtered on textured 130mm diameter NiP-plated aluminum substrates. A single sputtering parameter was varied to produce two types of films, labelled type I and type II, which exhibited significant differences in their magnetic recording characteristics.
Precipitates in hot pressed Nd-Fe-B magnets
Authors: Chu Tsung-Yao
Published: June 2020

High-performance permanent magnets based on the Nd-Fe-B ternary system can be prepared by melt-spinning of the molten alloy and subsequent pressing to full density at elevated temperature. The starting composition is always slightly rich in Nd compared to stoichiometric Nd2Fe14B in order to ensure the formation of the Nd-rich grain boundary phase. The excess Nd additions also serve to keep elemental Fe particles from precipitating but, instead, lead to unexpected precipitation within the Nd2Fe14B grains. The current research seeks to fully characterize the structure of the precipitates.

Electron transparent specimens for TEM examination were prepared by mechanical grinding of thin sections cut from the hot pressed Nd0.135Fe0.815B0.05 magnets, followed by argon ion beam milling at 6 kV. Most of the samples were studied in a JEOL 1200EX STEM equipped with EDS, operating at 120 kV. A few samples were examined at higher resolution in a JEOL 200 CX TEM operated at 200 kV, employing a side entry goniometer stage and a LaB6 cathode.