bluuebunny/crossref_metadata_2025_split huggingface dataset:
A combined TEM/APFIM approach to the study of phase transformations: Phase identification in the Fe-Be system
Authors: Burke M.G. , Miller M.K. 
Published: June 2020

Phase transformation investigations rely on the identification and characterization of the microstructure in order to understand the formation, development, and relative stability of the constituent phases. Although transmission and associated analytical electron microscopy techniques have made substantial contributions by providing structural and chemical data necessary for the detailed microstructural analysis, the direct atomic structure and chemistry are not readily discernable. By combining TEM techniques with atom probe field-ion microscopy (APFIM), it is possible to obtain a complete structural and chemical analysis of the constituent phases. In this paper, the microstructural development which occurs during ageing in an Fe-25 at. % Be alloy is presented to illustrate the complementary nature of the techniques and demonstrate the applicability of the combined TEM/APFIM approach in the study of phase transformations.An Fe-25 at. % Be alloy was solution annealed at 1100°C for 0.5 h and water-quenched prior to isothermal ageing at 650°C for 4 h. Thin foil specimens were examined in a Philips EM430T operated at 300 kV and in a JEOL 200CX operated at 200 kV. FIM needle specimens were electropolished and analyzed in the ORNL energy-compensated APFIM.
Rapidly solidified and thermally treated microstructures of beryllium-1wt.% Yttrium alloy
Authors: Jacobson L. A. , Martin P.L. , Mitchell T. E. 
Published: June 2020

Renewed interest in the possible use of beryllium at elevated temperatures has led to the examination of several dilute beryllium alloys with elements that form high melting point beryllide intermetallic compounds. One such alloying element is yttrium, which forms a beryllide, YBe13, with a melting point of over 1900° C. This system has been reported to have a eutectic between Be and YBe13at a composition under 1 wt% Y. 13 Dilute alloys in this system have been investigated as to their superplastic behavior.Samples were prepared by arc melting l0g buttons of Be-1wt% Y alloy, melting at least three times to promote homogeneity. Very small pieces of a button were then arc melted on a water cooled copper hearth and splat-quenched by means of a spring loaded hammer. Pieces of splat material were heat treated for 2h at 1000°C, and 3mm disks were punched out for subsequent twin jet electrolytic thinning and examination by transmission electron microscopy.
Observation by HVEM of the martensite transformation and the superconducting transition in Nb3Sn
Authors: Kirk M. A. , Baker M. C. , Kestel B. J. , Weber H. W. 
Published: June 2020

It is well known that a number of compound superconductors with the A15 structure undergo a martensite transformation when cooled to the superconducting state. Nb3Sn is one of those compounds that transforms, at least partially, from a cubic to tetragonal structure near 43 K. To our knowledge this transformation in Nb3Sn has not been studied by TEM. In fact, the only low temperature TEM study of an A15 material, V3Si, was performed by Goringe and Valdre over 20 years ago. They found the martensite structure in some foil areas at temperatures between 11 and 29 K, accompanied by faults that consisted of coherent twin boundaries on {110} planes. In pursuing our studies of irradiation defects in superconductors, we are the first to observe by TEM a similar martensite structure in Nb3Sn.Samples of Nb3Sn suitable for TEM studies have been produced by both a liquid solute diffusion reaction and by sputter deposition of thin films.
XTEM study of phase transition in MeV ion-implanted InP
Authors: Xiong Fulin 
Published: June 2020

MeV ion implantation into III-V compound semiconductors has attracted great attention in recent years because of its high potential for 3-dimensional device fabrication technology. However, a thorough understanding of associated physical processes involved is crucial before it can be universally applied. Our study on this subject with InP using cross sectional and high resolution transmission electron microscopy (XTEM, HRTEM) reveals clearly the structural changes occurring during MeV-ion-implantation and subsequent thermal annealing. It has lead to a better understanding of the mechanism of phase transition in InP under MeV ion irradiation.Samples of n-type InP(lOO) single crystalline wafers were implanted with 5 MeV-N-ions in room temperature with doses ranging from 1014 to 1016/cm2. Post-implantation annealing was carried out in a graphite strip heater at 500 C with ambient H2 flow.Fig. 1 shows a typical XTEM view of an implanted sample at a dose of 1 x 1016/cm2. A wide implanted layer is buried at a maximum depth of 4μm with a slightly damaged top surface. The buried layer appears as a highly disordered crystalline structure when the sample was annealed, whereas it is amorphous in an as-implanted sample.
Growth of hematite by surface oxidation of olivine
Authors: McKernan S. , Carter C. B. 
Published: June 2020

The oxidation of natural olivine has previously been performed on bulk samples and the reactions followed by preparation of TEM specimens from the annealed material. These results show that below ∼1000°C hematite and amorphous silica are formed, particularly around dislocations. At higher temperatures magnetite and some enstatite-like phase are formed. In both cases the olivine is left almost totally Fe depleted. By performing the oxidation on characterized thin TEM specimens it is possible to obtain more information on the nucleation and growth of the second phases formed. The conditions in a thin foil, however, are very different from those in the bulk especially with regard to surface effects. The nucleation of precipitates in particular may be expected to occur differently in these thin foils than in the bulk.TEM specimens of natural olivine (approximate composition Mg+Fe+Si2o4) which had been annealed at 1000°C for 1 hr were prepared by mechanical polishing and dimpling, followed by Ar ion milling to perforation. The specimens were characterized in the electron microscope and then heated in air in alumina boats to 900°C for between 30 and 180 minutes.
An overview of North American user facilities for electron microscopy in the physical sciences
Authors: Gronsky R. 
Published: June 2020

Physical scientists working in North America have access to five major User Facilities for advanced applications of electron microscopy. These Facilities are distributed geographically as shown in Figure 1, and provide a wide range of sophisticated instrumentation not normally found in the conventional electron microscope laboratory. Born of the need to maintain state-of- the-art equipment for research in the physical sciences and created because of the increasing cost and sophistication of such instrumentation, they operate on a “shareable” basis, having been funded by the government agencies to serve as regional and national resources, not for exclusive parochial access.The five facilities described here are: [1] the National Center for Electron Microscopy at the Lawrence Berkeley Laboratory, funded by the Department of Energy; [2] the Facility for High Resolution Electron Microscopy at Arizona State University, funded by the National Science Foundation; [3] the Center for Microanalysis of Materials at the University of Illinois, Urbana-Champaign, funded by both the Department of Energy and the National Science Foundation;
The National Facility for High Resolution Electron Microscopy at Arizona State University
Authors: Barry J. C. 
Published: June 2020

The National Facility for High Resolution Electron Microscopy, within the Center for Solid State Science at Arizona State University, was established in 1979 by the National Science Foundation. The Facility was established for the purposes of advancing knowledge in the field of high resolution electron microscopy, and promoting the application of new research methods to problems of current scientific and technological importance. The current Director of the Facility is Dr. John M. Cowley.The major equipment at the Facility is as follows.JEM 4000EX 400keV ultra-high resolution electron microscope (installed 1984). Structure resolution limit of 1.7 Å, and information limit of 1.6 Å. The 4000EX can be placed under computer control (using a system developed at ASU) for the purposes of alignment; that is, the computer automatically corrects the focus, stigmation and beam tilt. At 1.7 Å resolution, direct structure images of virtually all crystalline materials can be obtained, and individual atomic columns may be resolved in many samples. The 4000EX has been applied to characterization of defects, interfaces and surfaces of ceramics, metals and semiconductors.
The National Center for Electron Microscopy at Berkeley: An Update
Authors: Westmacott K. H. , Dahmen U. 
Published: June 2020

Since its establishment in 1984 the National Center for Electron Microscopy (NCEM) has provided a wide variety of users with advanced electron microscopy facilities for microstructural characterization. It has, in addition continued to develop and improve its resources to expand the range of features available to users.A major effort has been expended in building up a comprehensive computing facility to assist microscopists in optimizing instrument performance and extracting the maximum information from experimental data. The best currently available hardware has been assembled and a long menu of user-friendly software programs have been developed for general use. Sophisticated image simulation and image enhancement programs provide users of the Atomic Resolution Microscope all the necessary information for the correct interpretation of high resolution images. Direct links to both the ARM and the 1.5 MeV Kratos HVEM allow Fast Fourier Transforms to be performed, producing on-line diffractograms and greatly facilitating the effective and efficient use of the microscopes.
A very rapid in situ Kikuchi technique to determine relative crystal misorientation
Authors: Bennetch J. I. 
Published: June 2020

In a recent study of the superplastic forming (SPF) behavior of certain Al-Li-X alloys, the relative misorientation between adjacent (sub)grains proved to be an important parameter. It is well established that the most accurate way to determine misorientation across boundaries is by Kikuchi line analysis. However, the SPF study required the characterization of a large number of (sub)grains in each sample to be statistically meaningful, a very time-consuming task even for comparatively rapid Kikuchi analytical techniques.In order to circumvent this problem, an alternate, even more rapid in-situ Kikuchi technique was devised, eliminating the need for the developing of negatives and any subsequent measurements on photographic plates. All that is required is a double tilt low backlash goniometer capable of tilting ± 45° in one axis and ± 30° in the other axis. The procedure is as follows. While viewing the microscope screen, one merely tilts the specimen until a standard recognizable reference Kikuchi pattern is centered, making sure, at the same time, that the focused electron beam remains on the (sub)grain in question.
Modulated structure of superconducting Bi2CaSr2Cu2O8+δ
Authors: Gronsky R. , Fendorf M. , Fortunati K. , Hor P. , Meng R.-L. , Chu C.W. 
Published: June 2020

In the continuing search for new oxide superconductors, attention has recently been drawn to the Bi-Sr-Cu-O system by Michel et al who achieved a resistance drop onset at 22K for an ultrapure compound with composition Bi2Sr2Cu2O7+δ. Independent pursuits by the groups in Japan and Houston led to their simultaneous announcements of a new material with consistently high transition temperatures in the 100K range. This new compound is believed to have nominal composition Bi2Sr2Cu2O8+δ and orthorhombic unit cell dimensions of a = 5.44Å, b = 27.2Å, and c = 30.78Å. Subsequent electron microscopy investigations of the material identified both an incommensurate structure, and a two phase mixture, related structurally to the original Bi2CaSr2Cu2O8+δ phase. This investigation seeks further understanding of the microstructure of the new compound by a transmission electron microscopy study of single crystals (Tc = 85K) grown at the University of Houston.Specimens were prepared by crushing to a fine powder in an agate mortar, dispersing the powder in 200 proof ethanol, and suspending the particles on a holey carbon grid.
TEM analysis of TiSi2 on Si and polysilicon
Authors: Lewis Nathan , Shenai Krishna , Hall Ernest L. 
Published: June 2020

TiSi2, when deposited on poly-Si and Si, exhibits very low sheet resistance ana can be easily integrated into existing device and IC fabrication environments. However, the high temperature process stability of TiSi2 is rather limited. The silicide must be able to withstand processing temperatures in the 800°C-1000°C range for the fabrication of many high voltage devices and integrated circuits. In the present investigation the high temperature stability of the TiSi2 structures were examined using TEH on both planar and cross-sectional specimens.The starting materials in this study were <100> Si substrates doped with 1x1016 cm-3 boron. The gate SiO2 was grown and then the poly-Si deposited on the substrate followed by TiSi2 formation on the poly-Si, creating an actual MOS structure used for device fabrication. The TiSi2 was formed by rf sputtering of Ti followed by either a two-step thermal or rapid thermal anneal (RTA) to form the silicide.
Phase morphology studies of polyarylate/copolyester blends by transmission electron microscopy (TEM) and x-ray diffraction (XRD)
Authors: Plummer H. K. , Peters C. , Golovoy A. 
Published: June 2020

Injection molded blends of polyarylate (PAR) (ARDEL D-100,AMOCO) and a copolyester (PCTG) (PCTG-5445, EASTMAN CHEMICALS) were found to be single phase and transparent. Upon annealing, above the glass transition temperature, but below the melt temperature of each blend, a single glass transition temperature remained but blends up to 50% PAR become opaque due to crystallization of the PCTG. These morphological changes with annealing have necessitated this study.Cross sections of blends containing 85%, 70%, 50% and 30% PCTG, annealed at l60°C-1h, l60°C-4h, l85°C-4h and l85°C-16h respectively, were prepared for TEM using an LKB Ultramicrotome III with diamond knife. Thin, approx. 50 nm sections, supported on carbon film substrates on TEM grids were examined, as sectioned, by bright field TEM (BF TEM), in a JEOL 2000FX TEM operated at 200 keV. Additional thin sections of each blend were examined by BF TEM and selected area electron diffraction (SAED) after they were treated with a solvent mixture (methylene chloride(MeCl)/dioxane(Diox)) to remove the amorphous fraction and reveal the crystalline portion of the PCTG.
From tar sands to synthetic crude: Applications of microscopy
Authors: Mikula R.J. , Munoz V.A. 
Published: June 2020

The production of synthetic crude oil from tar sands is a complex process involving initial separation of the bitumen from the sand via the hot water process, separation of the bitumen from the water and finally coking of the residual bitumen to maximize the yield of crude oil. Many of the processing concerns center around decreasing the amount of water and clay which is carried with the bitumen product and decreasing the amount of bitumen which is carried with the water, sand and clay tailings. The crude oil yield in the final coking step is then dependent upon the efficiency of these preliminary steps as well as the coking conditions.Both electron and optical microscopy have important applications in understanding these systems. Direct observation of frozen hydrated samples in the electron microscope has been utilized for evaluation of both the size distribution of the dispersed phase and the chemical composition.
An HREM study of crystal imperfections in epitaxial lanthanide phthalocyanine films
Authors: Zhang W. P. , Kuo K. H. 
Published: June 2020

Because of their interesting electrochromic and gas-sensitive properties, lanthanide phthalocyanine (LnPc2H) films have received much attention recently. It is important to know the local structures of these films for understanding their chemical and physical behavior. LnPc2H is a sandwich-type complex (Fig. 1 (a)), with an ion at the center between two parallel phthalocyanine ligands which are rotated respectively by an angle of about 37°. As shown in Fig. 1 (c), two geometric isomers appear resulting from the different sense of rotation of two ligands. With the strong n-electron interaction between the molecular planes, these molecules tend to form molecular columns (Fig. 1 (b)) during crystal growth so that molecular images can be obtained along the column axis.Thin films of LnPc2H (Ln = Nd, Tb, Er, Tm, Yb and Lu) were epitaxially prepared on KC1 and NaCl substrates. The KC1 and NaCl crystals were cleaved along (100) in air and immediately placed into a vacuum evaporator.
Preparation and characterisation of vanadium pentoxide supported rhodium catalyst
Authors: Legrouri A. 
Published: June 2020

The industrial importance of metal catalysts supported on reducible oxides has stimulated considerable interest during the last few years. This presentation reports on the study of the physicochemical properties of metallic rhodium supported on vanadium pentoxide (Rh/V2O5). Electron optical methods, in conjunction with other techniques, were used to characterise the catalyst before its use in the hydrogenolysis of butane; a reaction for which Rh metal is known to be among the most active catalysts.V2O5 powder was prepared by thermal decomposition of high purity ammonium metavanadate in air at 400 °C for 2 hours. Previous studies of the microstructure of this compound, by HREM, SEM and gas adsorption, showed it to be non— porous with a very low surface area of 6m2/g3. The metal loading of the catalyst used was lwt%Rh on V2Q5. It was prepared by wet impregnating the support with an aqueous solution of RhCI3.3H2O.
Bevelled plan-view TEM specimen preparation and an artifact due to dimpling
Authors: Lee D.M. , Posthill J.B. , Rozgonyi G.A. 
Published: June 2020

The microstructure and metallic impurity gettering efficiency of misfit dislocation (MD) networks generated in Si/Si-2%Ge epitaxial films has been examined using TEM. Metallic elements were evaporated onto the top surface where alternating open windows and oxide masks were defined. The subsequent annealing permitted metal (i.e., gold in the present discussion) to diffuse through open windows into the wafer. The details of the sample structure and results can be found elsewhere in this proceedings. It is desirable to make microscopic observations in both cross-section and in plan-view. This contribution briefly outlines our procedure for making bevelled plan-view TEM specimens and describes a novel specimen preparation artifact.The top surface was treated with aqua regia (75% HCI, 25% HNO3) for a few seconds in order to remove the gold after the diffusion anneal. 2 mm square sections were cut from a gold diffused wafer and half of the top surface was polished at 2° angle with 6 μm and 1 μm diamond paste followed by final polishing with cyton using a vibrating lapping machine
High resolution scanned tip microscopies
Authors: Wickramasinghe H.K. 
Published: June 2020

The invention of Scanning Tunneling Microscopy (STM) which won the 1986 Nobel Prize in Physics has allowed one to image atoms on the surface of a metal or semiconductor by scanning a fine tip (whose diameter is 1000 Å in a controlled fashion very close (2Å) to the sample surface.In the STM, the tip to sample distance is controlled by measuring the tunneling current -i.e. the current that flows between the tip and sample when a voltage is applied between them- (which changes very rapidly with this distance) and using piezoelectric transducers to precisely position the tip in 3-dimensional space to lÅ accuracy. The STM responds to variations in the electron density of states of the sample surface.In this paper, we show how one can use the same piezoelectric positioning and control concepts demonstrated with the STM but rely on other physical interactions than the tunneling current to control the tip-sample spacing.
Some HREM observations on silicon small particles
Authors: Iijima Sumio 
Published: June 2020

In recent years, small particles have attracted the attentions of by some researchers for their physical and chemical anomaly as well as technological application to ceramics and catalyst industries. For these studies, morphological investigations on small particles seem to be important. HREM methods are the most direct approach to obtain particle crystal structures at atomic level resolution. This talk reviews some of the works on small particle research that have been done as a part of the fine particle research project by Japanese Research development Corporation (fully government-supported project). Among the many TEM observations on small particles that have been done, some specific problems using Si particles are presented.Small particle production Small particles of Si were prepared by a gasevaporation method which utilizes the evaporation and condensation of Si vapors in an Ar gas at 300Torr. The Si vapors were obtained by heating Si rods by an arc discharge1.
A high resolution experimental electron microscope for observations at liquid helium temperatures
Authors: Siegel Benj. M. , Shimoyama H. , Van Der Leeden E. 
Published: June 2020

We have developed a special experimental electron microscope for the study of radiation sensitive materials at high resolution. The most important features are related to the specimen environment which keeps the specimen under UHV conditions and at liquid He temperatures to minimize contamination and hopefully radiation damage. This instrument has been in operation for the past few years and a number of important modifications have been made that we wish to report on. The instrument is currently being set up to make systematic studies on radiation damage on materials at liquid He temperatures.The instrument is shown in the photograph in Fig. 1. The entire column is evacuated with three separate ion pumps, each pumping on a section of the microscope column; the illuminating system, the cryostat and the viewing chamber. Each section of the microscope can be closed off from the others by all metal gate valves. The illuminating and viewing chamber sections can be baked over 300°C to obtain an UHV.
Field emission scanning electron microscope
Authors: Aihara R. , Saito S. , Kohinata II. , Ogura K. , Otsuji H. 
Published: June 2020

A compact type field emission scanning electron microscope (JSM-F15) has recently been developed (Fig. 1). Moreover, due to the simplicity of the electron optical column and the automatically controlled ultra high vacuum system, a good quality and high resolution image can easily be obtained.The electron optical column, which is shown in Fig. 2, comprises a field emission gun, an electromagnetic lens, scanning coils, etc. The gun, which is composed of a field emitter, a wehnelt and an anode, is pre-aligned. The accelerating voltage is 15 kV and the emitter tip, made of tungsten single crystal, has a [310] orientation in the electron optical axis. The wehnelt is biased through a feedback circuit so as to maintain the emission current constant without varying the accelerating voltage.The electron probe current at the specimen surface is about 3 × 10-11 amp and the probe diameter is about 30Å at the working distance of 15 mm.