bluuebunny/crossref_metadata_2025_split huggingface dataset:
SEM and Field Mmission study of silicon field emitter array
Authors: Liu Jiang , Hren John J. 
Published: June 2020

Arrays of nanometer-scale field emitters have recently become attractive candidates for device applications where high frequency and high current are desirable attributes. High emission current can be obtained from densely packed Spindt-type emitter arrays with very low extraction voltage. Concern with the optimum geometrical shape of each emitter and the fraction of active emitters, makes a combined study of field emission and scanning electron microscopy especially useful.Several geometrical structures, as well as several materials, have been used to fabricate the field emitter arrays. The present study concentrates on silicon-base emitters fabricated at the Microelectronics Center of North Carolina (MCNC). Each emitter has a pyramidal structure, fabricated by anisotropic chemical etching of highly doped (ND = 1017 cm−3) n-type silicon. Figure 1 shows a SEM micrograph of a typical Si field emitter with a radius of curvature less than 30 nm. The field required for electron emission, about 3 × 107 V/cm, is created by a relatively low voltage applied to the extraction gate, a metal film less than one micron distant and deposited over a dielectric layer of silicon oxide (Figures 2 and 3).
UHV-STM studies of silicon nano-pyramid growth on silicon surface at high temperature
Authors: Sato T. , Kitamura S. , Sueyoshl T. , Iwatukl M. , Nielsen C. 
Published: June 2020

Recently, the growth process and relaxation process of crystalline structures were studied by observing a SI nano-pyramid which was built on a Si surface with a UHV-STM. A UHV-STM (JEOL JSTM-4000×V) was used for studying a heated specimen, and the specimen was kept at high temperature during observation. In this study, the nano-fabrication technique utilizing the electromigration effect between the STM tip and the specimen was applied. We observed Si atoms migrated towords the tip on a high temperature Si surface.Clean surfaces of Si(lll)7×7 and Si(001)2×l were prepared In the UHV-STM at a temperature of approximately 600 °C. A Si nano-pyramid was built on the Si surface at a tunneling current of l0nA and a specimen bias voltage of approximately 0V in both polarities. During the formation of the pyramid, Images could not be observed because the tip was stopped on the sample. After the formation was completed, the pyramid Image was observed with the same tip. After Imaging was started again, the relaxation process of the pyramid started due to thermal effect.
Ratio imaging of intracellular ion concentration
Authors: Bolsover Stephen R. 
Published: June 2020

The field of intracellular ion concentration measurement expanded greatly in the 1980's due primarily to the development by Roger Tsien of ratiometric fluorescence dyes. These dyes have many applications, and in particular they make possible to image ion concentrations: to produce maps of the ion concentration within living cells. Ion imagers comprise a fluorescence microscope, an imaging light detector such as a video camera, and a computer system to process the fluorescence signal and display the map of ion concentration.Ion imaging can be used for two distinct purposes. In the first, the imager looks at a field of cells, measuring the mean ion concentration in each cell of the many in the field of view. One can then, for instance, challenge the cells with an agonist and examine the response of each individual cell. Ion imagers are notnecessaryfor this sort of experiment: one can instead use a system that measures the mean ion concentration in a just one cell at any one time. However, they are very much more convenient.
Voltage dependence of the electron diffraction amplitudes in the ab initio analysis of copper perchlorophthalocyanine
Authors: Tivol W.F. , Turner J.N. , Dorset D.L. 
Published: June 2020

Copper perchlorophthalocyanine has become a model compound for exploring the application of electron microscopic and diffraction methods in high resolution molecular structure research. Because of the scattering contrast between the Cu and Cl heavy atoms and the lighter C and N atoms, it was not possible to determine the structure with electron diffraction data obtained at 100 kV a number of years ago. Dynamical scattering all but obscures the detail in the diffraction data due to the unit cell Fourier transform. Studies at 500 kV had also determined that the electron microscopic images were influenced by dynamic scattering. Since our HVEM can be operated from 100 kV to 1.2 MV in 100 kV steps, we are studying the influence of accelerating voltage on our ability to determine atomic-level molecular structure.We recorded electron diffraction patterns from crystals epitaxially oriented on KCl and tilted 26.5° relative to the beam in order to align the c-axis of the unit cell along the beam direction.
A novel approach to the identification of microcrystals with electrons
Authors: Le Page Y. 
Published: June 2020

Measurement of conventional-cell data requires observations along several specific zone axes in most cases. On the contrary, as shown in and outlined below, primitive-cell data can be extracted ab-initio, without trial-and-error, from single CBED patterns exposed along any zone axis, and displaying at least ZOLZ and first-order Laue-zone (FOLZ) spots.The CRYSTDAT database, which is up-to-date and accessible on-line, contains over 180,000 entries, each with cell data, chemistry and reference to published work for a compound. It can be searched for primitive cell data and partial chemistry. In combination with the previous remark, this shows that crystallites can be identified from single CBED patterns, and from partial chemical information obtained on them by Energy-Dispersive X-ray spectroscopy.CBED patterns are analyzed as follows. Two-dimensional (xP.vP) cartesian coordinates are measured for centers of all diffraction spots on the CBED film from an arbitrary origin. To each Bragg spot P on the film corresponds a scaied reciprocal vector FS with projections on the three axes:
The structure of amorphous and polycrystalline materials using energy-filtered RDF analysis
Authors: Cockayne David , McKenzie David 
Published: June 2020

The technique of Electron Reduced Density Function (RDF) analysis has ben developed into a rapid analytical tool for the analysis of small volumes of amorphous or polycrystalline materials. The energy filtered electron diffraction pattern is collected to high scattering angles (currendy to s = 2 sinθ/λ = 6.5 Å-1) by scanning the selected area electron diffraction pattern across the entrance aperture to a GATAN parallel energy loss spectrometer. The diffraction pattern is then converted to a reduced density function, G(r), using mathematical procedures equivalent to those used in X-ray and neutron diffraction studies.Nearest neighbour distances accurate to 0.01 Å are obtained routinely, and bond distortions of molecules can be determined from the ratio of first to second nearest neighbour distances. The accuracy of coordination number determinations from polycrystalline monatomic materials (eg Pt) is high (5%). In amorphous systems (eg carbon, silicon) it is reasonable (10%), but in multi-element systems there are a number of problems to be overcome; to reduce the diffraction pattern to G(r), the approximation must be made that for all elements i,j in the system, fj(s) = Kji fi,(s) where Kji is independent of s.
Progress in electron energy loss spectroscopy of Cu-ZSM-5 zeolite
Authors: Liu D. R. 
Published: June 2020

The copper containing zeolite Cu-ZSM-5 recently has attracted worldwide attention due to its ability to decompose nitrogen oxides (NOx) , an undesirable constituent of vehicle exhaust. Faced with the problem of NOx control in lean burn engines designed to improve fuel economy, this zeolite is thought to hold the promise of more efficient catalytic converters for NOx. An effort was therefore made to characterize this material with a JEOL-2000FXII analytical electron microscope.Fine powder samples of Cu-ZSM-5 and H-ZSM-5 were acquired from a vendor and analyzed in a comparative study. The AEM specimens were made either by placing a droplet of a fine powder suspension on a carbon coated grid, or by microtoming a resin embedded block of the zeolite and collecting thin sections on a grid. Fig. 1 is a high resolution micrograph taken in the channel direction (the b-axis) of the zeolite crystalline structure along with the diffraction pattern from the same area (Fig. 2). Both Cu-ZSM-5 and H-ZSM-5 samples showed the same structure images in all lattice orientations. These results are consistent with the published x-ray diffraction data on the ZSM-5 zeolite lattice structure.
Imaging small particles with secondary electrons
Authors: Liu J. , Spinnler G. E. , Ron A. E. 
Published: June 2020

High resolution secondary electron microscopy (HRSEM) in dedicated scanning transmission electron microscopy (STEM) instruments has proved very useful for characterizing supported catalysts. In order to understand the contrast mechanisms of HRSEM images of small particles, clean samples and UHV environments are needed since the emission of secondary electrons (SEs) can be significantly influenced by contamination on the particle surface. In this paper we report results on imaging small metal particles by HRSEM in a UHV STEM instrument. In addition, we show that with computer assistance digitized HRSEM images of small metal particles can be used to estimate the average inelastic mean free path and the mean escape depth of the collected SEs.The Vacuum Generators UHV STEM HB-501S, codenamed MIDAS (a Microscope for Imaging, Diffraction and Analysis of Surfaces), was used for these experiments. Detailed descriptions of the MIDAS system have been published previously. The collection efficiency of SEs approaches 100% through the use of magnetic ‘parallelizers’ situated inside the objective pole pieces.
Magnification Errors in the SEM
Authors: Geller Joseph D. 
Published: June 2020

Test and inspection instrumentation requirements are becoming more stringent, as evidenced by the International Standards Organization ISO-9001 certification. To qualify for certification it will be mandatory to calibrate and maintain calibration on laboratory instrumentation. The semiconductor industry also requires accuracies in the sub-micrometer range. However, “the SEM does not always tell the truth”. This work addresses magnification accuracy.Magnification accuracy in the scanning electron microscope (SEM) is affected by the instruments design, manufacture, calibration, and its operating environment. In order to check and calibrate the instrument a standard is required. The only currently available NIST (National Institute of Standards and Technology) magnification standard for the SEM (SRM-484) measures in one dimension and only at higher (> 1000X) magnifications. Recognizing that microscopy is by nature two-dimensional we need to calibrate SEMs in both the X & Y dimensions. A suitable standard has been developed which is usable at least over the normal range of SEM accelerating voltages (200eV and higher) and magnifications (10X to 50,000X).
Application of the Sterecon System for the Determination of Area, Volume, and Linear Distance of Cell Surface Topography of Secondary and Backscatter Electron Stereoscopic Images in Low-Voltage Field Emission SEM
Authors: Erlandsen Stanley L. , Wells Carol L. , Olmsted Stephen B. , Leith ArDean , Marko Michael 
Published: June 2020

Extraction of quantitative information on surface topography in SEM can.be accomplished with, stereoscopic visual parallaxes. This method has received little attention in the last decade and to our knowledge has not been applied to high resolution secondary or backscatter electron images from field emission SEM. The STERECON system was developed for 3-D reconstruction of cells from stereo images obtained by high voltage EM. The present study describes the application of STERECON to quantitative determination of volume, surface area, and linear distance of topographical features in high resolution SEM.Trophozoites of the free-living protozoan, Hexamita inflata, and two bacterial species (Proteus mirabilus and Enterococcus faecalis) were fixed in 2.5-3.0% glutaraldehyde, dehydrated in ethanol, critical point dried in CO2, and coated with about 1 nm of platinum before examination at low kV (<4.0) in a Hitachi S-900 field emission SEM equipped with secondary (Se) and backscatter (YAG scintillator) detectors and photographed on Polaroid type 52 film using a stereo tilt of 8°.
SEM studies of fracture phenomena and wall structure in micrometeoroid impact craters in spacecraft metals
Authors: Murr L. E. , Niou C-S. , Rivas J. M. , Quinones S. , Advani A. H. 
Published: June 2020

There has been a considerable effort over nearly a decade to examine the size frequencies, compositions, and origins of particles producing impact craters in a variety of materials surfaces on the Solar Maximum Mission spacecraft, retrieved communications satellites (such as Palapa-B2), and more recently the LDEF (Long Duration Exposure Facility) spacecraft. Three regimes of particles have emerged: natural cosmic dust or interplanetary dust particles (IDP's), man-made orbital debris (including paint or other spacecraft component or coating chips having compositions different from the impacted materials); and orbital debris, often spacecraft debris or secondary (ejecta) debris, having the same composition as the impacted material. However more than 50% of all LDEF impacts into metallic targets did not yield sufficient projectile residue to permit analysis using EDS techniques in electron beam instruments (SEM or STEM in particular).There have been very few attempts to investigate the microstructural and microchemical nature of the micrometeoroid crater walls, especially in the context of the integrity of the wall in relation to the target metal, and the propensity for cracking and crack nucleation within the crater wall.
Nickel L2,3 core energy loss studies in NiSi2
Authors: Wong Kaikee , Silcox John 
Published: June 2020

The L2 and L3 edges in EELS spectra of 3d transition metals arise primarily from dipole excitation of the 2p1/2 and 2p3/2 electrons to unfilled 3d states. Since the initial states have narrow energy widths, the L2,3 edges reflect the conduction band density of states (DOS) with d character. By comparing the Ni L2,3 edges in NiSi2 to those in pure Ni, the bonding between Ni and Si can be studied.Experiments were carried out in an UHV HB501A STEM operating at 100 keV with a serial EELS spectrometer. The spot size and the current were estimated to be 5 Å and 0.1 nA respectively. Both the convergence and the detector angles were about 11 mrad. The spectra were recorded in steps of 0.25 eV for Ni and 0.5 eV for NiSi2. Long dwell times were necessary to achieve high signal to noise ratio in the core loss spectra and typically 5 sec per energy step was used.
Characterization of TiSi2/TiN thin films on Si by HREM
Authors: Sharma Renu 
Published: June 2020

Titanium Nitride is commonly used as a diffusion barrier layer in Al-Si contacts. There are different techniques employed to deposit TiN layers on silicon, out of them thermally grown and reactively sputtered are most common. Reactive sputtering is a one step process and is favoured for manufacturing. The orientation of TiN thin films controls the orientation of Al films deposited. As sputtered films has random orientation hence the overlying Al films is randomly oriented as well. In order to achieve higher electromagnetic resistance, Al films should be well oriented. Thermally grown TiN thin films are highly oriented but their thickness is limited to about 20nm. We have used HREM and micro-analytical techniques to analyze the thickness, structure and compositions of various layers formed during thermal growth of TiN layers deposited under different conditions.Thermally grown Ti films on Si <100> wafers of varying thicknesses were deposited and annealed in NH3 atmosphere at different temperatures and times. Second layer of titanium was deposited and processed on some of the samples (double process) in order to increase the thickness of TiN layer.
Electron microscopy studies of PZT ferroelectric film capacitor structures
Authors: Kaushik V. , Maniar P. , Olowolafe J. , Jones R. , Campbell A. , Hance R. , Mogab C.J. 
Published: June 2020

Lead zirconium titanate films (Pb (Zr,Ti) O3 or PZT) are being considered for potential application as dielectric films in memory technology due to their high dielectric constants. PZT is a ferroelectric material which shows spontaneous polarizability, reversible under applied electric fields. We report herein some results of TEM studies on thin film capacitor structures containing PZT films with platinum-titanium electrodes.The wafers had a stacked structure consisting of PZT/Pt/Ti/SiO2/Si substrate as shown in Figure 1. Platinum acts as electrode material and titanium is used to overcome the problem of platinum adhesion to the oxide layer. The PZT (0/20/80) films were deposited using a sol-gel method and the structure was annealed at 650°C and 800°C for 30 min in an oxygen ambient. XTEM imaging was done at 200KV with the electron beam parallel to <110> zone axis of silicon.Figure 2 shows the PZT and Pt layers only, since the structure had a tendency to peel off at the Ti-Pt interface during TEM sample preparation.
Time-of-flight secondary ion mass spectrometry of bulk polymers using patterned silver overlayers to enhance the molecular microanalysis of trace additives
Authors: Mawn M. P. , Linton R. W. , Benninghoven A. 
Published: June 2020

When coupled to a time-of-flight (TOF) mass analyzer which provides a high transmission, quasi-simultaneous detection of secondary ions, and theoretically unlimited mass range, secondary ion mass spectrometry (SIMS) is well suited for submonolayer molecular analysis of solid surfaces. Additionally, molecular ion images may be obtained by using a focused primary ion beam rastered on the sample surface to provide lateral distributions of chemical species.TOF-SIMS has been shown effective at characterizing low level polymer additives such as UV absorbers, thermal stabilizers, anti-oxidants, and slip agents in polymer extracts deposited on roughened Ag substrates. Additionally, in-situ analysis of linear low density polyethylene (LLDPE) samples using TOF-SIMS has provided information on surface segregation and surface oxidation. The polymer extract analysis has the advantage of both preconcentrating the polymer additives, as well as providing enhanced ion yields through Ag canonization. However, the in-situ analysis is also a valuable approach since it alleviates the time consuming extraction procedure and provides information on additive surface segregation and oxidation.
Characterization of frozen hydrated biological specimens by low-loss EELS
Authors: Sun Songquan , Leapman Richard D. 
Published: June 2020

Analyses of ultrathin cryosections are generally performed after freeze-drying because the presence of water renders the specimens highly susceptible to radiation damage. The water content of a subcellular compartment is an important quantity that must be known, for example, to convert the dry weight concentrations of ions to the physiologically more relevant molar concentrations. Water content can be determined indirectly from dark-field mass measurements provided that there is no differential shrinkage between compartments and that there exists a suitable internal standard. The potential advantage of a more direct method for measuring water has led us to explore the use of electron energy loss spectroscopy (EELS) for characterizing biological specimens in their frozen hydrated state.We have obtained preliminary EELS measurements from pure amorphous ice and from cryosectioned frozen protein solutions. The specimens were cryotransfered into a VG-HB501 field-emission STEM equipped with a 666 Gatan parallel-detection spectrometer and analyzed at approximately −160 C.
X-ray microanalysis of right ventricular guinea pig myocytes for correllation with NMR measurements of intracellular NA changes after ouabain treatment
Authors: Hagler Herbert K. , Butwell Nina B. , Bellotto Dennis , Malloy Craig R. 
Published: June 2020

It is well known that ouabain, a cardiac glycoside, can be used to increase left ventricular contractility. One of the proposed mechanisms of action is the inhibition of Na-K ATPase which leads to an accumulation of Na, which in turn stimulates Ca accumulation via Na-Ca exchange. It has been suggested that the increased calcium is responsible for the augmentation of contractile force. Preliminary studies were designed to measure the intracellular concentrations of Na, Cl, K, and Ca by X-ray microanalysis of freeze-dried cryosections and to compare this data with measurements of intracellular Na made using shift reagent aided 23Na NMR spectroscopy.Male guinea pigs were anesthetized, the hearts excised and perfused using a Langendorff preparation at a pressure of 70cm H2O and at 37°C. A Krebs-Henseleit solution bubbled with 95% O2 - 5% CO2 was used. Ouabain at a concentration of 3 × 10-7 M was added to the perfusate for 30 minutes. This ouabain concentration produces an ionotropic effect without producing a measurable increase in the amount of intracellular sodium as measured by NMR.
Evaluation of the ZAF procedure employed in the NIST/NIH DTSA program
Authors: Myklebust Robert L. 
Published: June 2020

The ZAF matrix correction procedure employed in the Desk Top Spectrum Analyzer program (DTSA) is considerably different from the FRAME matrix correction program from which it was derived. Enough differences exist that an evaluation of the results of quantitative analyses performed with the program needed to be done. The DTSA program is capable of providing all the peak intensities for each element analyzed; therefore, all of the peak fitting and background fitting functions were removed from the FRAME program. Also, since the database incorporated into DTSA contains all of the peak energies and the excitation energies (absorption edge energies) for all x-ray lines, the fitting procedures for computing these energies were removed from the FRAME program.An important change now in the the ZAF procedure is the computation of the atomic number correction. The absorption correction and the characteristic fluorescence correction are unchanged. A continuum fluorescence correction has not yet been included in the program.
Fast new simulation of x-ray signals for arbitrary geometries
Authors: Wang Xinlei , Joy David C. 
Published: June 2020

The Bremsstrahlung spectrum from a bulk specimen has been successfully studied with high accuracy by Monte Carlo techniques. However, such procedures take considerable computing time since any change of experimental parameters requires a fresh computation. This paper describes an alternative approach which allows x-ray signals for a given structure to be computed within a fraction of a second. The method is illustrated here by an application to Bremsstrahlung. The procedure used is that of a diffusion matrix in which the strength of individual diffusion sources is derived by an initial Monte Carlo computation.The grid of a diffusion matrix Φ(yi,zj,Ek) which is established by Monte Carlo simulation contains the intensity of Bremsstrahlung x-ray coordinated at yi,zj with the photon energy of Ek. In the simplest case the matrix can be computed so that any photon crossing all the cells is accumulated. The results are stored in a 20×40×30 matrix for -R<zj<R and 0<yiR in steps of R/20 where R is the Bethe electron range, and 0<Ek<E0 in steps of E0/30. The accuracy of the matrix depends on the quality of the Monte Carlo simulation used to generate it.