bluuebunny/crossref_metadata_2025_split huggingface dataset:
The study of interfacial reactions of nickel thin films on GaAs
Authors: Chen L.J. , Hsieh Y.F. 
Published: June 2020

One measure of the maturity of a device technology is the ease and reliability of applying contact metallurgy. Compared to metal contact of silicon, the status of GaAs metallization is still at its primitive stage. With the advent of GaAs MESFET and integrated circuits, very stringent requirements were placed on their metal contacts. During the past few years, extensive researches have been conducted in the area of Au-Ge-Ni in order to lower contact resistances and improve uniformity. In this paper, we report the results of TEM study of interfacial reactions between Ni and GaAs as part of the attempt to understand the role of nickel in Au-Ge-Ni contact of GaAs.N-type, Si-doped, (001) oriented GaAs wafers, 15 mil in thickness, were grown by gradient-freeze method. Nickel thin films, 300Å in thickness, were e-gun deposited on GaAs wafers. The samples were then annealed in dry N2 in a 3-zone diffusion furnace at temperatures 200°C - 600°C for 5-180 minutes. Thin foils for TEM examinations were prepared by chemical polishing from the GaA.s side. TEM investigations were performed with JE0L- 100B and JE0L-200CX electron microscopes.
EBIC microscopy for the characterization of semiconductor materials and devices
Authors: Varker C. J. 
Published: June 2020

For dislocation-free silicon crystals, defects generated during semiconductor device fabrication processes are often the end result of inhomogeneities formed during crystal growth. Impurity-point defect complexes are often transformed into a variety of microdefects during subsequent thermal processing. Extensive investigations have been published on the analysis of microdefects such as stacking faults, complex dislocation colonies and impurity precipitates in silicon crystals. For crystals grown with the Czochralski method, oxygen and carbon have been the subject of many recent investigations. Oxygen precipitation during thermal annealing has been identified as a dominant cause of minority carrier lifetime degradation. The investigative methods used in the majority of these studies include: transmission electro microscopy, scanning electron microscopy, I.R. absorption spectroscopy, X-ray transmission methods and chemical decoration etching.Conventional electron microscopy provides no direct information on the relationship between defects in crystals and electrical effects in semiconductor devices.
Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels
Authors: Chen L.J. , Cheng H.C. , Gong J.R. , Yang J.G. 
Published: June 2020

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).
Fracture toughness relationships in a low-alloy steel
Authors: Padmanabhan R. , Wood W. E. 
Published: June 2020

Utilization of high austenitization temperatures to improve fracture toughness of UHSLA steels at similar strength levels has received considerable interest. However, these heat treatments result in reduced ductility and impact toughness. This inverse response of impact and plane strain fracture toughness is essentially due to microstructural effects and it is possible to achieve simultaneous improvements in all these properties through controlled variations in the microstructure.A vacuum remelted Si-modified 4340 steel was chosen for this study under three heat treated conditions, viz., conventional, high temperature and step with austenitization temperatures of 1143 K (1 hr), 1473 K (1 hr) and 1473 K (1 hr) furnace cooled to 1143 K (5 min), respectively. All samples were quenched in oil and tempered at 553 K (1 hr). A modified conventional heat treatment was also designed to achieve a desired microstructure with a 1143 K (1 hr) austenitization, a 923 K (1 hr) intermediate temper (after oil quenching), a 1123 K (3 min) reaustenitization and a final 553 K (1 hr) temper (after requenching) steps.
Coherency loss in γ' precipitates in nickel-base superalloy
Authors: Ricks R. A. , Porter Angus J. 
Published: June 2020

During a recent investigation concerning the growth of γ' precipitates in nickel-base superalloys it was observed that the sign of the lattice mismatch between the coherent particles and the matrix (γ) was important in determining the ease with which matrix dislocations could be incorporated into the interface to relieve coherency strains. Thus alloys with a negative misfit (ie. the γ' lattice parameter was smaller than the matrix) could lose coherency easily and γ/γ' interfaces would exhibit regularly spaced networks of dislocations, as shown in figure 1 for the case of Nimonic 115 (misfit = -0.15%). In contrast, γ' particles in alloys with a positive misfit could grow to a large size and not show any such dislocation arrangements in the interface, thus indicating that coherency had not been lost. Figure 2 depicts a large γ'	precipitate in Nimonic 80A (misfit = +0.32%) showing few interfacial dislocations.
Phase chemistries in a precipitation-strengthened superalloy
Authors: Hall E. L. , Kouh Y. M. , Chang K. M. 
Published: June 2020

The majority of Ni-base superalloys are strengthened by precipitation of the γ' phase, which has a coherent ordered Ll2 structure based on Ni3(Al,Ti). However, a few superalloys, most notably Inconel 718, are strengthened instead by a γ" phase, which is a metastable coherent ordered DO22 precipitate with a tetragonal unit cell and nominal stoichiometry Ni3(Nb,Ta). The γ' phase generally precipitates homogeneously in the form of spheres or cubes, whereas the γ" phase occurs as disks with the (001) γ" plane parallel to one of the {100} planes of the cubic matrix. Thus, three variants of γ" are possible. The γ" phase is generally metastable and is replaced on extended aging by the δ phase, which is also Ni3(Nb,Ta) but which has a Cu3Ti-ordered orthorhombic structure.It has been shown that the type of precipitate formed in Ni-base alloys is a sensitive function of overall alloy chemistry. In particular, the Ti+Al/Nb+Ta ratio has a strong effect, with increases in this ratio favoring γ and decreases γ'.
The crystal morphology of 2:17 rare-earth cobalt permanent magnets
Authors: Hadjipanayis G. C. , K. R.  
Published: June 2020

Precipitation hardened Sm2(Co,Fe,Cu,Zr)17 permanent magnets are of great technological importance because of their large coercive fields (Hc∽ 6-15 kOe) and energy products ((BH)m ∽	25-30 MGOe). The hard magnetic properties of these magnets are usually achieved after a complex heat treatment. The samples are first sintered at 1200 C and then quenched to room temperature. The sintered magnets are aged at around 830 C, slowly cooled to 400 C and then quenched again to room temperature. Microstructure studies have been reported on several 2:17 magnets at their optimum state. The purpose of this study is to examine the changes in the microstructure that are produced by the described heat treatment and determine how they affect the hard magnetic properties of the magnets. Samples of a commercial TDK REC-26 magnet (Sm(Co,Fe,Cu,Zr)7.5) were prepared at different stages of the heat treatment. Electropolishing together with ion thinning were used to prepare the specimens for transmission electron microscopy. The microstructure observations were made with a Philips 400 TEM equipped with an energy dispersive x-ray analysis unit.
In situ annealing of aluminum ion-implanted with molybdenum
Authors: Bentley J. , Stephenson L. D. , Benson R. B. , Parrish P. A. 
Published: June 2020

As part of an analytical electron microscopy study of aluminum ion-implanted with molybdenum, in situ annealing experiments have been performed to better understand the phase transformation mechanisms in material with a peak molybdenum content of approximately 11 at. % Mo. Ion implantations were performed at the Naval Research Laboratory on electropolished coupons 38 × 28 × 0.5 mm of 99.999% Al with 0.5 mm grain size. A dual energy implant schedule of 1.12 × 1020 ions/m2 at 50 keV. plus 1.24 × 1020 ions/m2 at 110 keV was employed. The TEM specimens were prepared by electrodischarge machining 3-mm diameter disks from the implanted coupons and backthinning by electropolishing. In situ annealing was performed in a Philips EM 400T/FEG with the use of a Philips single-tilt heating holder. Videotape recordings were made from the TEM fluorescent viewing screen in the tilted position.A high concentration of small dislocation loops and possibly a tangled dislocation network were present in the as-implanted material. No precipitates were observed; this is consistent with a supersaturated solid solution.
Decomposition of the metastable beta titanium alloy Ti-15-3
Authors: Chen Y. L. , Fujlshiro S. 
Published: June 2020

Metastable beta titanium alloys have been known to have numerous advantages such as cold formability, high strength, good fracture resistance, deep hardenability, and cost effectiveness. Very high strength is obtainable by precipitation of the hexagonal alpha phase in a bcc beta matrix in these alloys. Precipitation hardening in the metastable beta alloys may also result from the formation of transition phases such as omega phase. Ti-15-3 (Ti-15V- 3Cr-3Al-3Sn) has been developed recently by TIMET and USAF for low cost sheet metal applications. The purpose of the present study was to examine the aging characteristics in this alloy.The composition of the as-received material is: 14.7 V, 3.14 Cr, 3.05 Al, 2.26 Sn, and 0.145 Fe. The beta transus temperature as determined by optical metallographic method was about 770°C. Specimen coupons were prepared from a mill-annealed 1.2 mm thick sheet, and solution treated at 827°C for 2 hr in argon, then water quenched. Aging was also done in argon at temperatures ranging from 316 to 616°C for various times.
Rocking curves for specular reflection from crystal surfaces in the TEM
Authors: Turner P. S. , Eades J. A. 
Published: June 2020

In transmission electron microscopy, electron diffraction is most frequently undertaken in the “Laue condition” (i.e. the electron beam entering one surface of a parallel sided slab and leaving through the opposite surface) or some approximation to it. In contrast, surfaces studies by RHEED are carried out in the “Bragg condition” (i.e. the electron beam enters and leaves through the same surface of the crystal and the Bragg reflection is from planes parallel rather than perpendicular to the surface).Now that high quality images from surfaces are being obtained in reflection e.g., Yagi, it is appropriate to develop diffraction techniques for the Bragg condition in the electron miroscope; there are many examples of such work in RHEED equipment e.g. The symmetric Bragg condition is obtained when the incident and diffracted beams make the same angle with the specimen surface; this is specular reflection. Thus to obtain a rocking curve in the symmetric Bragg case requires variation of both the incident beam angle and the take off angle. This is not practical in an unmodified microscope.
Attractive and repulsive forces between clusters: A STEM study of platinum clusters
Authors: Chen E. G. , Ohtsuki M. , Crewe A. V. 
Published: June 2020

Zanghi et al. measured the radial distribution functions of gold clusters on a KC1 substrate before and after annealing, and interpreted their results as indicating that a repulsive force exists between each pair of clusters. However, these results may be insufficient to explain the clustering phenomenon in all cases. For instance if this were the only force involved then coalescence could not occur. However, coalescence always occurs in the forming of thin films.We present experimental results and some theoretical considerations of the interactive forces applied to the clustering of platinum deposited on a thin carbon film of about 20Å thickness. The ultra high vacuum (UHV)-STEM and digital image processor were used for the measurements of the size (d) and edge to edge (r-d) distributions (see Fig. 1).
A thin-section technique for transmission electron microscopy of catalysts
Authors: Hall J. B. , Hruskoci P. P. 
Published: June 2020

Transmission electron microscopy (TEM) is often used to image the different phases, the metal dispersion, and the pore structure of heterogeneous catalysts. Although fine particle dispersion ts the most common sample preparation method because of its simplicity, it suffers from a paucity of sample areas which are thin enough. A less common technique for catalysts is thin sectioning. Sprys et al reported that the thin section technique is prohibitively expensive due to damage to the diamond knife, although Sawruk et al reported satisfactory results using a diamond knife with a relatively large angle (55°). An improved thin section technique has been developed for catalysts which has proven to be practical and efficient. Three catalysts have been used to evaluate and compare these preparation techniques.The fine particle dispersion technique used in this evaluation involves spraying a suspension of the finely ground catalyst onto a holey Triafol film covered grid.3 Figure 1 is a SFM micrograph of an area of a TEM grid with a catalyst sample prepared by this technique. Most of the particles lying on the holey film are obviously too thick for TEM.
Electron-diffraction studies in synthetic polymer materials
Authors: Grubb D.T. 
Published: June 2020

Diffraction studies in polymeric and other beam sensitive materials may bring to mind the many experiments where diffracted intensity has been used as a measure of the electron dose required to destroy fine structure in the TEM. But this paper is concerned with a range of cases where the diffraction pattern itself contains the important information.In the first case, electron diffraction from paraffins, degraded polyethylene and polyethylene single crystals, all the samples are highly ordered, and their crystallographic structure is well known. The diffraction patterns fade on irradiation and may also change considerably in a-spacing, increasing the unit cell volume on irradiation. The effect is large and continuous far C94H190 paraffin and for PE, while for shorter chains to C 28H58 the change is less, levelling off at high dose, Fig.l. It is also found that the change in a-spacing increases at higher dose rates and at higher irradiation temperatures.
Light element analysis of irradiation-induced precipitates in Ti-modified 316 stainless steel
Authors: Thomas L. E. 
Published: June 2020

G and n phases are complex nickel silicides which commonly form in Fe-Ni-Cr based stainless steels and superalloys during neutron irradiation at 400-600°C. Both phases are cubic and are structurally similar to the common carbides M2 3C6 and M6C which form in many of the same alloys during thermal aging. Although G and n have been analyzed previously by energy-dispersive x-ray spectrometry (EDXS), little is known about their carbon contents.To further determine the compositional relationships between the G/n silicides and the M 23C 6/M6C carbides, an irradiated Ti-modified 316 stainless steel specimen containing 0.05 to 0.5μm particles of G and n was analyzed by means of electron energy loss spectroscopy (ELS) and EDXS in a field emission gun scanning transmission electron microscope (STEM). The alloy, LSI, has the nominal composition of Fe-16.8Cr-13.5Ni-l.9Mo-0.87Si-2.0Mn-.15Ti-.045C and was irradiated to 2 x 1022n/cm2, E >0.1 MeV, at 510°C in the EBR-II breeder test reactor.
A controller for safe, convenient operation of LaB6 emitters on electron-beam instruments
Authors: W. J. Abramson  , Estry H. W. , Allard L. F. 
Published: June 2020

LaB6 emitters are becoming increasingly popular as direct replacements for tungsten filaments in the electron guns of modern electron-beam instruments. These emitters offer order of magnitude increases in beam brightness, and, with appropriate care in operation, a corresponding increase in source lifetime. They are, however, an order of magnitude more expensive, and may be easily damaged (by improper vacuum conditions and thermal shock) during saturation/desaturation operations. These operations typically require several minutes of an operator's attention, which becomes tedious and subject to error, particularly since the emitter must be cooled during sample exchanges to minimize damage from random vacuum excursions. We have designed a control system for LaBg emitters which relieves the operator of the necessity for manually controlling the emitter power, minimizes the danger of accidental improper operation, and makes the use of these emitters routine on multi-user instruments.Figure 1 is a block schematic of the main components of the control system, and Figure 2 shows the control box.
Automatic focus control system for scanning electron microscope (Model S-570)
Authors: Otaka T. , Yamada O. , Saito S. , Watanabe T. 
Published: June 2020

We have developed an automatic focus control and astigmatism correction system for electron microscopes. Fig. 1 shows the Model S-570 SEM.In the scanning electron microscope focusing operation at high magnifications (several thousand times or higher) requires a great deal of skill and experience. The Automatic Focus Control System enables this difficult operation to be done automatically. Fig. 2 shows the principle of the detecting system of focus.The electron beam is converged on a specimen by an objective lens and the signal emitted from the specimen is detected by a detector as an imaging signal. Waveform of the imaging signal is sharp at optimum focus conditions and consequently its differential signal shows a large peak height. On the other hand, when the focus condition is not optimum, the imaging signal is smooth and the differential signal shows small peak height. The Automatic Focus Control is a system in which focus condition is regulated automatically so that peak height of the differential signal becomes maximum.
Correlation of x-ray and electron crystallography of biological structures
Authors: Caspar Donald L. D. 
Published: June 2020

The development of electron crystallography of biological structures recapitulates in many ways the history of x-ray crystallography started by W.L. Bragg in 1913 and, more particularly, protein crystallography begun by Bernal and Crowfoot Hodgkin in 1934. By the early 1950s Perutz and Bragg were mapping the outline of the hemoglobin molecule by tracing the molecular transform through the use of a kind of negative staining for x-ray diffraction. The demonstration by Perutz and his colleagues that the isomorphous replacement method could be used to solve the phase problem in protein crystallography opened the way to determining the atomic structure of proteins starting with myoglobin.Electron crystallography was begun by Klug and his colleagues in the mid 1960s using optical diffraction to detect periodicities in the image and then applying optical filtering to separate superimposed two-dimensional lattice images and to average the image of the repeating unit. Following the underlying unity in the optics of image formation and diffraction of light, x-rays and electrons, DeRosier and Klug developed the theory and methodology of three-dimensional image reconstruction with the use of Fourier transforms of digitized images.
High-resolution structural analysis of purple membrane
Authors: Henderson R. , Baldwin J.M. , Agard D.A. , Leifer D. 
Published: June 2020

Two crystal forms of the purple membrane from Halobacterium halobium are being investigated. One is the native p3 form which occurs naturally, and the other is an orthorhombic p22121 form which is made artificially with detergent.Both forms diffract to better than 3 Å resolution. They have been studied by electron diffraction at high (3 Å) resolution, and at lower resolution (6.5-7 Å) by electron microscopy. Both crystal forms occur as membrane sheets, containing a single molecular layer of protein molecules with a lipid bilayer filling the space between the protein molecules, the whole having a thickness of about 45-50 Å. The electron microscopic and diffraction analyses have been carried out in three dimensions using specimens tilted at angles of up to 60° to the incident electron beam.The resulting Fourier maps of the two structures enable a common shape for a single molecule of bacteriorhodopsin to be determined, which is free of the ambiguity of molecular boundary normally found in crystal structure analyses at lower resolution than that required to trace the path of the polypeptide chain.
Electron crystallography of crotoxin complex thin crystals
Authors: Jeng T.W. , Chiu W. 
Published: June 2020

Crotoxin complex is a neurotoxin isolated from the venom of the South America rattlesnake, Crotalus durrissus terrificus. It consists of two dissimilar subunits, one very acidic and the other very basic. Both acidic and basic subunits are required to show its neurotoxicity. The toxin attacks novally on both the pre-synaptic and the post-synaptic sites of the neuro-muscular junction.This protein has been crystallized in thin platelet forms suitable for electron crystallographic studies and an electron diffraction pattern of a glucose embedded crotoxin complex crystal has been recorded to an atomic resolution. The space group of this thin crystal was determined to be P4222 by a combination of electron microscopic techniques. In each unit cell, there are 8 crotoxin complex molecules arranged in a 4 layer configuration along the c axis. Different crystals have been found to have different thicknesses. We have been able to determine whether the diffraction data is obtained from a crystal with a half or a full unit cell by calculating the crystallographic reliability factors from the digitized electron diffraction pattern and by measuring optical density of a low magnification image recorded immediately after each electron diffractign pattern.
Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin
Authors: Tivol William F. , King Murray Vernon , Parsons D. F. 
Published: June 2020

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.