bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Field Emission Electron Gun for High Resolution 100KV Electron Microscope
Authors: Someya T. , Goto T. , Harada Y. , Watanabe M. 
Published: June 2020

The field emission source is one of the most important factors to improve the image contrast in extremely high resolution electron microscopy since it provides high brightness, very small electron source and low energy spread of electrons. In scanning electron microscopy, although the field emission source has been proved to be advantageous in the range of relatively low accelerating voltages, those capable of operating at higher accelerating voltages are now in great demand in order to improve the resolving power up to 3Å or better. In the present work, we have developed a field emission electron gun which is used with an electron microscope of accelerating voltages up to 100KV.In this development, we first made efforts to improve the method of supplying high voltages in order to eliminate the surge influence on the field emission source which are easily destroyed by a high voltage surge produced by the discharge between electrodes constituting the electron gun.
A Resolution Test Sample for the Scanning Electron Microscope
Authors: Ballard David B. 
Published: June 2020

A test sample that satisfies the restrictive specimen criteria discussed previously for a resolution determination of the SEM is essential. At present, the use of a resolution sample made from a specimen well-known to the particular operator who carries out measurements on the subsequent photomicrograph is the usual procedure. The aluminum-tungsten (Al-W) dendritic structure (located at arrow) in Fig. 1 that remains on the crystal surface of the bead resulting from the melting of aluminum on a hot tungsten filament, provides such a specimen.The dendritic structure found on the Al-W specimen and shown in Fig. 2 is produced by the following technique. A piece of high purity aluminum (99.999%) wire weighing 35 to 40 milligrams is attached to a single coil, approximately 4mm O.D., of a tungsten filament made from 0.5mm (20 mil) single strand wire. The length of the tungsten filament, between the clamped ends of the electrodes in the metal evaporator, is about 6cm.
High Voltage Electron Microscopy of Integrated Circuit Devices
Authors: Smith P. J. , Troutman H. A. , Raheja R. K. 
Published: June 2020

One-MEV transmission electron microscopy has been used to examine the complete structure of individual integrated circuit devices. The use of high voltage microscopy provided sufficient penetration to examine the entire emitter and base regions, while a new specimen preparation technique ensured that the device was uniformly thinned.As previously reported, a TEM specimen preparation technique has been developed which uses the structure of the device itself to form the thinned sample. This technique has been used to prepare samples which are uniformly thin over the entire area of the device. Thus the complete characterization of the defect structure within the device is possible; this is necessary if a direct relationship between structure and electrical properties is to be made. Samples approximately 3 μ m thick were prepared so that the complete emitter and base regions and part of the collector could be examined by high voltage transmission microscopy. The emitter-base and collector-base junctions were 1.7 μ m and 2.1 μ m deep respectively. The base dopant was boron and the emitter dopant was phosphorous.
Ion Thinning of Sensitive Materials
Authors: Thompson George R. 
Published: June 2020

As the list of materials prepared by ion micro milling has increased over the last few years, experience has been gained regarding the families of materials which are most sensitive to ion bombardment. Based on our laboratory experience, it has become necessary to develop certain attachments for ion etching machines which may be used to eliminate or minimize the deleterious effects of this process on sensitive materials. In summary, these mechanisms of damage may be categorized as thermal effects, structural alterations (artifacts), ion damage, surface contamination and differential etching. In addition to citing examples of these various categories, attachments and processing techniques used to protect sensitive materials from damage are summarized.Thermally sensitive materials were first ion etched under cryogenic conditions in the latter part of 1970. The requirement for ion etching at relatively low temperatures arose in conjunction with research on electronic materials, and the masking employed in conjunction with circuit etching.
Effects of High-Energy Ions on Synthetic Quartz
Authors: Comer Joseph J. , Bergeron Charles , Lowe Lester F. 
Published: June 2020

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.
Elevated Temperature Stability of a Lamellar Al-CuAl2 Eutectic Composite
Authors: Pattnaik Amitav , Lawley Alan 
Published: June 2020

Since the two phases of a directionally solidified binary eutectic composite are essentially in chemical equilibrium, the microstructure should be stable at elevated temperatures. This effect has been demonstrated in a number of alloys. However, eutectic composites are characterized by physicochemical instability due to the large total interfacial area. The total interfacial energy per unit volume can be reduced by coarsening of the structure, by the growth of existing lower-energy interfaces at the expense of existing higher-energy interfaces, or by the formation of new lower-energy interfaces at the expense of existing interfaces. The present study was made in order to examine these possibilities in a fine-scale lamellar Al-CuAl2 eutectic.Composites with an interlamellar spacing ≲2 μ were grown at a speed of 11 cm per hour in high-purity graphite crucibles. Exposure temperatures of 490°C, 510°C and 530°C were chosen with time at temperature ranging from 10 to 100 hours.
Hardening Effect and Electron Metallography of Precipitation in Uranium with Small Additions of Titanium
Authors: Johnson D. H. , Ammons A. M. 
Published: June 2020

Uranium-0.5 wt.% titanium and U-1.0 wt.% Ti alloys are alpha-phase, martensitic uranium alloys which show large increases in strength due to precipitation of U2Ti on aging at moderate temperatures. Hardness, electron microscopy, and X-ray diffraction were used to study growth kinetics of the U2Ti precipitation and the precipitate-matrix interactions.The alloys were induction melted from high-purity uranium and sponge titanium in a zirconia-coated graphite crucible and bottom poured into a zirconia-coated mold; subsequently, the alloys were solution treated at 800°C for one hour in a vacuum of 5 x 10-6 torr and water quenched. Small specimens were then heat treated at temperature in a vacuum of 5 x 10-6 torr and water quenched.Thin foils were prepared by a modification of the two-step electrothinning procedure of DuBose and Stiegler from rods using 15 volume percent perchloric acid and 35 volume percent butyl cellosolve in methanol for initial thinning and a bath of 6 volume percent perchloric acid cooled with a dry ice-acetone mixture for the final electropolishing.
Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs
Authors: Ansley David A. 
Published: June 2020

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic
Comparison of Simulated Images With Electron Images of Lactic Dehydrogenase
Authors: Fiskin A. Max , Mack Patricia 
Published: June 2020

Comparison of negative stain images of glutamate dehydrogenase (GDH) with shadow projections of opaque models has revealed that this approach can be misleading. We have suggested an x-ray simulation procedure in which the influence on the image of disruption of oligomer, finite metal-ion complex size, and depth of the stain layer are simulated under controlled conditions, and have deduced a model of GDH quaternary structure using this procedure.Here the accuracy of procedure suggested above is tested by comparing micrographs of rabbit muscle lactic dehydrogenase (LDH) with simulated images obtained with a model of dogfish LDH constructed in accord with x-ray diffraction data. The dogfish and rabbit muscle LDH's exhibit extensive sequence homology, are each composed of four subunits, and have nearly identical molecular weights. Dogfish LDH exhibits 222 symmetry and the shape of the oligomer approximates a parallelepiped.
Construction and Application of Environmental Cell
Authors: Fukami A. , Katoh M. 
Published: June 2020

The key points of constructing an environmental cell are an environmental window frame which transmits electron beam from vacuum to the cell, and an environmental window film put on the frame.From our experimental results, the window frame is made from a copper aperture having a 300 μmϕ hole covered with a copper screen having 40 μmϕ holes, and the window film is made from doubly vacuum-evaporated film which consists of carbon layer (350 Å in thickness, facing to vacuum side) and silica or silicon carbide layer (150 Å, facing to atmospheric side), using the micro grid technique developed by us). Carbon layer has high mechanical strength against to the difference in pressure between in and out of the cell (0.01 to 760 Torr.), and silica or silicon carbide layer has desirable durability for electron irradiation in gases. The thickness of atmospheric space is controled by a spacer (10 to 200 μm), and a specimen is generally put on the window film facing to the objective lens.
Formation of Dislocation Channels in Neutron Irradiated Molybdenum
Authors: Mahajan S. 
Published: June 2020

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.
Reduction of Radiation Damage in Organics by Cooling to 4K and Embedding
Authors: Knapek E. , Formanek H. , Lefranc G. , Dietrich I. 
Published: June 2020

Structure determination of organic, in particular biological, material is performed with x-ray methods, if sufficiently large crystals are available. In the case of small periodic regions a good tool is electron diffraction. However, the information gained with this method will in general hardly do. The necessary additional data can be obtained e.g. by direct imaging with the electron microscope. Unfortunately structure changes due to the electron impact make imaging very difficult with a resolution below 20 Å. Recently it has been established that radiation damage can be drastically reduced by cooling the specimen to 4 K1 or by embedding it in an amorphous matrix. In the following the radiation protection achieved by combining both methods is shown on the example of the organic complex Cu-bis-salicyloylhydracin (Cu-BSH) which is interesting for cable technology.The specimens are prepared by solving BSH in NH3 and subsequently adding copper tretamin solution. The needle-shaped crystals which precipitate are spread on holey carbon foil (Fig. 1). Diffraction patterns were taken at room temperature and at 4 K.
Platinum-TiO2 (Rutile) Substrate Interaction During Cyclic Oxidation-Reduction Heat-Treatment
Authors: Shinozaki S. , Donlon W. T. , Meitzler A. H. 
Published: June 2020

When polycrystalline TiO2 (rutile) pellets (∼1mm in thickness and ∼3 mm in diameter), dispersed with Pt particles to act as a catalyst, were heat-treated under certain conditions involving an applied electric field, new unusual microstructures were formed. The heat-treatment procedure was, as follows: 1) apply 1 volt dc field between two Pt electrodes inbedded into the pellet, 2) heat the sample to 750°C and begin cycling the sample between oxydizing (4% O2 in N2) and reducing (2% CO in N2) atmospheres at a rate of several cycles per hour, 3) lower the temperature to 600°C while continually cycling (200 cycle), and, 4) cool the sample to room temperature under the reducing atmosphere (1). The pellet was ion milled to a proper electron transparency and examined by means of a Siemens EM102 and a Philips EM400 TEM-STEM microscope.Some TiO2 grains in this sample exhibited no resolvable defect structure, except that the matrix appeared to be strained due to small defects (Fig. la).
Interpretation of High Resolution Lattice Image of Thick Crystal
Authors: Ishizuka K. , Iijima S. 
Published: June 2020

A wealth of information on structural details in the images of thick crystals has been demonstrated. This paper is concerned with interpretation of the HREM images of thick crystals.To save the cost of the HREM image calculation, a computation method for the multislice formulation will be economical. Our previous studies of a crystal of niobium oxides showed that the HREM images appearing in thin regions recurred in thicker regions (Fig. 1). The simulation of this recurrence would be a measure to judge the validity of the calculation. The calculated amplitudes for some beams contributing to the image are shown in Fig. 2. The HREM images corresponding to the thicknesses indicated in Fig. 2 are simulated using our experimental parameters. The recurrence of the image is reproduced clearly in this calculation (Fig. 1). The result is encouraging for the analysis of thick crystals in terms of their structural details.
Observations of Pt-Ir on Al2O3 Catalysts Using a Fast Digital System Controlled STEM
Authors: Butler J. H. 
Published: June 2020

The familiar Scanning Transmission Electron Microscope (STEM) technique of Z-contrast, used to image heavy atoms on amorphous supports, can be applied to the study of metal catalysts with only partial success. The contrast is reduced when crystalline systems are studied since a Bragg contribution is introduced in the standard annular dark-field collector. At large angles, the Bragg reflections diminish due to thermal vibrations; and the scattering cross section is approximately proportional to Z2. Thus scattering in this region is predominately Rutherford-like. The atomic number dependence of this high angle detectoro (HAD) signal makes it particularly suited for identifying small (20-50Å diameter) catalyst particles suspended in polycrystal line alumina.The experimental configuration for this imaging mode suggests concurrent acquisition of the HAD signal and the corresponding bright field signal , as on-line arithmetic of the two is necessary to optimize image contrast. In the conventional STEM it is impossible to detect the HAD signal because it is cut off by the specimen cartridge. Treacy, et al. have developed a sophisticated method for obtaining these signals.
Flash Tube Radiation Annealing of BF2-Implanted Silicon
Authors: Chen L. J. , Lu L. Z. , Lue J. T. 
Published: June 2020

Laser and electron beam annealing of ion-implanted semiconductor are currently of great interest as alternatives to thermal annealing. It is known that unconventional annealings are essentially extensions of thermally induced recovery and regrowth processes which are dependent on power density, annealing time and energy balance. The annealing mechanism does not seem to depend on the coherence of the source. Any source capable of applying short and intense heat pulses should suffice for rapid annealing. For large areas processing and economic considerations, a high power density, short pulse flash tube radiation annealing may be more advantageous than other unconventional annealing methods. With appropriate control, light pulses from flash tube heat up the surface layer of ion-implanted silicon very rapidly and may anneal out the damage or recrystallize the amorphous layer.Two inches in diameter and about 10 mil in thickness wafers of 3-5 Ω-cm, phosphorus doped, (001) and (111) oriented silicon were implanted at room temperature with 100 keV BF+2 ions to doses of 1 x 1014 to 1 x lO16/cm2. A demountable flash tube was used to anneal the samples with 100 μsec FWHM pulses and energy density (ED) ranging from 19.6 to 41.1 J/cm2. The fill pressure of air was kept beloe 30 torr. Optical and scanning electron microscopy (OM and SEM) were used to study the changes of silicon surface after annealing. Transmission electron microscopy (TEM) was performed to investigate the microstructural changes. Four point probe method was applied to measure the sheet resistivity.
Application of TEM to the Characterisation of Commercial BaTiO3 Capacitors
Authors: Mecartney M. L. 
Published: June 2020

Ferroelectric BaTiO3 with its high dielectric constant is a material widely used for miniature high capacitance capacitors. Pure BaTiO3 has the perovskite crystal structure (cubic) above 120°C and undergoes a phase transformation to a ferroelectric state at 120°C: the electric dipole is created as the Ti+4 ion shifts slightly along a <100> direction, resulting in a slightly tetragonal structure (c/a 1.01). Ferroelectric domains form to minimize strain energy. Commercial polycrystalline BaTiO3 contains various impurities and dopants and the purpose of this TEM study is to assess whether similar behaviour occurs compared to the pure material.BaTiO3 capacitors from several industrial sources were examined, containing up to several atomic per cent of various oxides (Bi, Zr, Sn, Ca) which stabilize the high dielectric constant over a wide range of temperatures and “tie up” oxygen vacancies. Previous TEM work in the present study using EDS has shown that the presence of impurities prevents the ferroelectric phase transformation and the formation of ferroelectric domains at room temperature. No ferroelectric domains exist in region A of fig. 1(d) where Bi, Sn, and Ca impurities were detected, while conversely in the ferroelectric region B no impurities could be found. (Delta fringes from overlapping ferroelectric domains delineate the ferroelectric portion of the grain.) It is thought that impurity ions substituting on the BaTiO3 lattice distort the lattice sufficiently to prevent the phase transformation from occuring.
Localisation and Momentum Transfer in Inelastic Scattering
Authors: Howie A. 
Published: June 2020

With the more positive and precise utilisation of a wide variety of inelastic signals now made possible by STEM, microscopists ask questions going beyond the established theory of charged particle scattering. Because of its relevance to resolution and contrast, particular interest attaches to the degree of localisation of these interactions, but this has received only limited attention in earlier work, e.g. ion channelling, particle track structure.A fast electron with velocity v, scattering through an angle θ with energy loss ΔE =θEmv2, experiences a momentum transfer. The corresponding impact parameter b is, by the uncertainty principle, roughly given bybut a more precise approach evaluates the scattering from a suitably localised initial wave function (e.g. a Gaussian) to a final state plane wave accepted by the detector (fig.1). The scattering amplitude as a function of b can be calculated from the more familiar plane wave scattering amplitudes by Fourier integration.
The Combined Effect of Channelling and Blocking in Electron Energy Loss Spectroscopy
Authors: Taftø J. , Krivanek O. L. 
Published: June 2020

Bragg reflection of electrons gives rise to a modulation of the wavefield over the crystal unit cell. Depending on the incident beam direction the electrons may be concentrated at one or another type of atoms or between them. Localized ionization processes will therefore show an orientation dependence, and this will affect the X-ray emission intensities as well as electron energy loss spectra. The energy loss case gives more possibilities for experimental arrangements than the X-ray emission case, in that the direction of not only the incident electron beam, but also that of the exit beam to be analyzed may be selected.Natural MgAl2O4spinel was studied. The crystals were ground in a mortar and thin areas were analyzed with a Gatan 607 spectrometer attached to a Philips 400T electron microscope operating at lOOkV. The experiments were done for the (400)-planar case where the main atomic planes contain Al2O4. The Mg-atoms are midway between the A12O4and may be considered as interstitials in this planar case.
Application of EELS to the Study of Metal-Hydrogen Systems
Authors: Zaluzec N. J. , Schober T. , Westlake D. G. 
Published: June 2020

The study of metal-hydrogen systems is becoming increasingly important in various energy technologies today, and as a consequence it becomes desirable to be able to characterize the resulting phases as accurately as possible. In this paper we report a preliminary study of metal-hydrogen systems using the technique of electron energy loss spectroscopy (EELS) in an analytical electron microscope (AEM).The study of hydrogen in rare earth metals using EELS was first reported by Colliex et al. in 1976; in that work as well as in this study the characteristic energy loss of plasmon scattering was measured in various metal and hydride phases. Plasmon scattering in general is related to electronic structure of the material and thus the formation of a hydride phase if it affects the electronic structure of the alloy is expected to produce characteristic changes in the energy loss distribution.