bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative determination of modulation transfer function and detection quantum efficiency for standard and anti-reflection YAG scintillator slow-scan CCD-camera
Authors: Weickenmeier A.L. , Nüchter W. , Mayer J.
Published: June 2020

Introduction
The modulation transfer function (MTF) of a slow-scan CCD camera (Gatan modell 679 attached to our Zeiss EM 912 Omega) has been determined with high precision for the standard and the new anti-reflection YAG scintillator. It is shown that deconvolution of experimental patterns allows the reconstruction of image details down to pixel size. From the analysis of deconvoluted noise patterns we found that for this camera the detection quantum efficiency (DQE) is 0.6 in the typical working range of 300 to 3000 electrons per pixel and does not depend on the scintillator. A full discussion of this work can be found in.

Experiment
To determine the point spread function (PSF) we punched a hole in a sheet film holder which then was partially covered by one or two knife edges (slit). These masks were projected onto the scintillator. About 600 line scans perpendicular to the edge or slit were extracted and averaged to reduce noise (Fig. 1).
New approaches to characterizing advanced materials
Authors: Smith David J.
Published: June 2020

Motivations for using the electron microscope are obviously many and varied. For example, engineers in the semiconductor industry might be primarily interested in establishing reasons for device failure. Chemists in the petrochemical industry could be concerned with analyzing the composition and structure of novel catalytic materials. Many researchers seek to characterize microstructure and establish definitive connections with preparation conditions and/or some pertinent macroscopic behavior. Instrumentation for the high-resolution electron microscope (HREM) has continued to evolve to the extent that imaging on the atomic scale and microanalysis on the sub-nanometer scale are oftentimes available from the same microscope. Such instruments are thus highly attractive to all those people interested in characterizing advanced materials. Our purpose here is to provide a brief overview of some recent developments in instrumentation and techniques and to highlight their relevance for materials science applications.
Evaluation of phonon scattering in electron diffraction using image plates and electron energy filtering
Authors: Høier R. , Kim M.Y. , Zuo J.M. , Spence J.C.H. , Shindo D.
Published: June 2020

There have been few studies of thermal diffuse scattering (TDS) by electron diffraction although this scattering is easily observed. The TDS intensity distribution is as a rule strongly anisotropic which can be ascribed to scattering from individual phonon modes. Results reported so far in the literature are all based on qualitative or semi-quantitative use of the observed intensity distributions. However, at present several new methods (energy filters, imaging plate, CCD, digitized film) are available to extract data for detailed quantitative interpretation. In the present work the Zeiss 912 Omega energy filtering microscope has been used, combined with the Fuji Imaging Plate and a low temperature specimen holder. This opens new possibilities both for the study of soft modes and other TDS phenomena related to phase transitions, and also static disorder and order-disorder effects. By comparison with synchrotron work on TDS , crystals may be very much smaller and count rates are much higher. However, multiple scattering and Kikuchi lines may complicate the interpretation unless thin samples are used.
High-resolution electron microscopy of nanostructured materials
Authors: José-Yacamán M.
Published: June 2020

Electron microscopy is a fundamental tool in materials characterization. In the case of nanostructured materials we are looking for features with a size in the nanometer range. Therefore often the conventional TEM techniques are not enough for characterization of nanophases. High Resolution Electron Microscopy (HREM), is a key technique in order to characterize those materials with a resolution of ~ 1.7A. High resolution studies of metallic nanostructured materials has been also reported in the literature. It is concluded that boundaries in nanophase materials are similar in structure to the regular grain boundaries. That work therefore did not confirm the early hipothesis on the field that grain boundaries in nanostructured materials have a special behavior. We will show in this paper that by a combination of HREM image processing, and image calculations, it is possible to prove that small particles and coalesced grains have a significant surface roughness, as well as large internal strain.
Aggregation growth of nanometer-sized BaTiO3 particles
Authors: Chun C. M. , Navrotsky A. , Aksay I. A.
Published: June 2020

Nanocrystalline BaTiO3 particles are synthesized under hydrothermal conditions by the reaction of nanosized TiO2 colloids with aqueous solutions of Ba(OH)2 at 80°C. A dissolution-precipitation mechanism is proposed for the formation of BaTiOs by this route, because suspended TiO2 nano-particles dissolve into Ba(OH)2 solution, supersaturate the solution phase, and subsequently precipitate BaTiOs particles. The origin of the rough "raspberry-like" BaTiOs particles during growth stages can be explained by one of two mechanisms: (i) the morphological instability at the growth front during continuous growth, or (ii) aggregation of colloidal particles by multiple clustering. Our TEM studies on samples prepared by controlled seeding experiments show that a multiplicity of low or high angle grain boundaries occur during growth, supporting the aggregation growth.

In order to separate the nucleation step from the growth step more efficiently, seed BaTiO3 particles were prepared by adding TiO2 colloids (Degussa, P-25) to 2.23 M Ba(OH)2 solution and hydrothermally reacting at 80°C under atmospheric pressure for 48 hours in polyethylene bottles. The resulting seed particles were recovered by centrifugation, rinsed with C02-free deionized water and freeze-dried.
Intergrainular structure and deformation mechanism in nanocrystalline materials
Authors: Ye H.Q. , Ping P.H. , Li D.X. , Huang J.Y. , Wu Y.K.
Published: June 2020

It is recognized that boundary structure (GB) characterization is essential in order to understand the structure-properties relationship of nanocrystalline (NC). In most cases, NC materials have to suffer deformation during compacting or ball milling techniques, a deep and systematic study on deformation mechanism is also necessary. In this paper, characterization of microstructure in NC materials synthesized by three methods has been presented.

1. Ordered and Disordered Regions at GBs of NC Pd
The NC Pd samples were synthesized by the inert gas condensation and in situ compacting technique. The results of X-ray diffraction and HREM observations showed that the average grain size of the NC Pd is about 10 nm. It can be seen that most of the GBs have ordered structure and no 'gas-like' feature has been observed. Some disordered GB regions, such as nanovoid formed during compacting process, are also detected as marked by "V" in Fig.l. The structural modification from the disordered state was found during in situ HREM investigation.
Stabilizing aqueous clay suspensions by AOT vesicular solutions: a cryo-TEM study
Authors: Li Xiangbing
Published: June 2020

Production, storage, and performance of suspensions of colloidal solid particles depend critically on suspensions stability. Past studies mostly focused on roles of attractive van der waals force and repulsive electrostatic force between particles. In contrast, this paper reports that aqueous suspensions of clay particles of maximum dimension of 5 to 20 nm can be greatly stabilized by adding vesicular solutions of the anionic surfactant Aerosol OT (AOT).

How does the interaction between the clay particles, which bear charge, and multiple bilayers of AOT vesicles lead to more stable suspensions? Cryogenic transmission electron microscopy (cryo-TEM) was brought to bear on this question because it can capture the microstructure in fluids without staining or drying artifacts. Cryo-TEM samples were made by rapidly freezing thin liquid films (200-500 nm) in a controlled environment vitrification system (CEVS)5 to preserve the original structures. Clay particles (often hexagonal) were flat plates and tended to associate face-to-face (Fig. la). Cryo-TEM images show that 3 wt% and 5 wt% AOT formed unilamellar and multilamellar vesicles in solutions (Fig. lb-c).
In situ irradiation effects studies in medium- and high-voltage TEM
Authors: Allen Charles W.
Published: June 2020

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.
In-Situ crystallization of nano-wires and dots by electron irradiation in a field-emission TEM/STEM
Authors: Libera M.
Published: June 2020

Specimen damage and heating by high-energy electron irradiation can be exploited to affect local specimen composition/temperature to drive phase transformations. Field-emission (FEG) sources are especially prone to inducing damage/heating, because their high brightness provides focused ~1nm FWHM/1.0nA probes. The physics of beam heating and damage are reviewed by Reimer (1,2). Heating is related to energy-loss mechanisms broadly summarized by the Bethe formula for stopping power. Radiation damage can cause atomic displacement, ionization, and bond scission. Displacement increases the point-defect concentration. Composition changes occur when displacements eject atoms from the specimen. This paper outlines first results using focused-probe irradiation in a Philips CM20 FEG TEM/STEM to locally crystallize an amorphous 80nm Ge48Te52 film. Ex-situ annealing leads to spherulitic crystallites. The crystallization kinetics have been studied by time-resolved reflectivity (3) and in-situ hot-stage optical microscopy (4). In-situ TEM annealing was done with a single-tilt hot stage. Films were floated from carbon-coated mica onto Cu grids. In-situ annealing under a parallel (low dose) beam leads to crystallization much like the ex-situ studies except that the crystallite morphology is highly anisotropic due to non-uniform film heating (5).
In situ grain growth study in electrodeposited nanocrystalline Nil.2WT.%P alloy
Authors: Smith D. A. , Mehta S. C. , Erb U.
Published: June 2020

Nanocrystalline (nc) materials, owing to their ultrafine grain sizes, exhibit several physical and mechanical properties which are significantly different from, and in many cases, superior to those of their polycrystalline counterparts and therefore promise their usage in a number of applications. However, very poor resistance of nc pure metals against thermal grain growth severely limits the application of these novel materials. Several attempts are being made to improve the thermal stability of nc materials. The conventional approaches of grain boundary pinning by second phase precipitates and solute drag effects are commonly being employed. However, the kinetics of grain growth and the roles of solute atoms and second phase precipitates in affecting grain growth inhibition in these nanolength scale materials are still not well understood.

A transmission electron microscope study has been made of the microstructural evolution of electrodeposited nanocrystalline Ni-1.2wt.%P alloy and pure nickel during heating experiments performed in-situ.
In Situ Atomic Force Microscopy of Pt/Ti film morphology changes on a microelectronic gas sensor operating at elevated temperatures
Authors: DiBattista M. , Patel S. V. , Mansfield J. F. , Gland J. L. , Schwank J. W.
Published: June 2020

Thin film electronic devices that employ resistance change responses of Pt / Ti films to detect gas species have been microfabricated at the University of Michigan. Atomic force microscopy (AFM) is used to investigate morphology of the Pt / Ti sensing films deposited on the microfabricated device. These Pt / Ti sensing films are strongly influenced by many factors, making it difficult to determine the exact relationship between film structure, chemical sensitivity, and selectivity. In-situ AFM investigations of Pt / Ti films on this device at elevated temperatures provides the opportunity for real time observation of film morphology changes under controlled conditions, testing sensing film stability during device operation, and correlating film structure to resistance.

Observation of the Pt / Ti film surface and in-situ resistance measurements at elevated temperatures are possible due to the construction of the sensing device. The sensors are based on chemically active thin films deposited on a micromachined silicon window, supported by a 300 μn thick silicon rim.
In situ study of electron beam-induced chemical vapor deposition of Au in an environmental TEM
Authors: Drucker J. , Sharma R. , Kouvetakis J. , Weiss K.H.J.
Published: June 2020

Patterning of metals is a key element in the fabrication of integrated microelectronics. For circuit repair and engineering changes constructive lithography, writing techniques, based on electron, ion or photon beam-induced decomposition of precursor molecule and its deposition on top of a structure have gained wide acceptance Recently, scanning probe techniques have been used for line drawing and wire growth of W on a silicon substrate for quantum effect devices. The kinetics of electron beam induced W deposition from WF6gas has been studied by adsorbing the gas on SiO2surface and measuring the growth in a TEM for various exposure times. Our environmental cell allows us to control not only electron exposure time but also the gas pressure flow and the temperature. We have studied the growth kinetics of Au Chemical vapor deposition (CVD),in situ, at different temperatures with/without the electron beam on highly clean Si surfaces in an environmental cell fitted inside a TEM column.
Energy filtered magnetic domain imaging at 400 kV
Authors: Nuhfer N.T. , Dooley J. , De Graef M.
Published: June 2020

Lorentz microscopy provides an important technique for the study of advanced magnetic recording media. Recording densities as high as 10 Gbit/in may be within reach in the future. Microstructural characterization of both the crystallographic and magnetic structure of these thin films is needed at the highest spatial resolution. Another area where Lorentz microscopy has proven to be an extremely valuable tool is in magnetic actuator applications, in particular for magnetostrictive alloys, such as Terfenol-D. The standard Lorentz techniques (Fresnel and Foucault imaging) require a low-field environment, so that the sample is not completely saturated during observations. Depending on the microscope type this low-field area can be obtained by either switching off the objective lens and using the weak post-field to focus the image, or by using special low-field pole pieces. The attainable magnification in both cases is usually lower than for conventional TEM. Recently a new low-field lens for the JEOL 4000EX TEM was reported (AMG40, 1 Gauss field strength) with a useful magnification range upto × 200,000. In this paper we report an alternative method to obtain high magnification magnetic domain images at 400 kV.
Application of AEM to chemical and structural characterization of the AlN-Al2O3 and AlN-Al2O3-SiO2 Systems
Authors: Westwood A. D.
Published: June 2020

The thermal, electronic and mechanical properties of aluminum nitride (A1N) make it an attractive material to a number of technologically important areas; microelectronic packaging, high temperature semiconductors, opto-electronic and piezoelectric devices and structural ceramics. It is well established that the concentration and distribution of impurities can control the macroscopic properties of materials. A1N is a classic example, with oxygen (O) being the dominant controlling impurity. The role of O in point defect formation and its detrimental effect on thermal conductivity was first documented by Slack. Oxygen has subsequently been shown to cause the formation of two-dimensional extended defects of which two variants exist, planar and curved. Both defects have been identified as O-rich inversion domain boundaries (IDB´s) (Fig.l). Because of the controlling influence that O has on thermal conductivity, it is important to fully understand the defect structures and chemistries that exist as a result of O incorporation. A1N-A12O3 is a prototype system for understanding the role that non-stoichiometry (impurities) plays in IDB formation.
Formation of polytype microstructure in pulsed-laser-irradiated sapphire substrates
Authors: Cao Siqi , Pedraza A. J. , Allard L. F. , Lowndes D. H.
Published: June 2020

Surface modifications of wide-gap materials are produced by pulsed laser irradiation. Under given conditions, these near-surface modifications can promote adhesion enhancement of deposited thin film materials, and activation for electroless deposition. AIN decomposes during laser irradiation leaving a metallic film on the surface. High density dislocations were observed in the surface layer of AIN that was laser melted but not decomposed. The laser melted alumina becomes amorphous at a laser energy density of ~1J/cm2. In sapphire, γ-alumina is formed when the sample is laser irradiated in Ar/4%H2. Here, we report the formation of a new structure in laser-irradiated sapphire.

Optically polished c-axis sapphire substrates were laser-irradiated in an Ar/4%H2 atmosphere at 4J/cm2 energy density, using a 308 nm-wavelength laser with a pulse duration of ~40 ns. Sapphire (A12O3) has a space group R 3 c and can be described as an hcp structure having oxygen and aluminum layers alternately stacking along the c-axis.
Relationship between structure and mechanical properties of ion-irradiated MgAl2O4 spinel
Authors: Devanathan Ram , Yu Ning , Sickafus Kurt E. , Nastasi Michael
Published: June 2020

The relationships between structure and properties of irradiated materials is an important focus of radiation damage studies. A knowledge of these relationships can enable us to tailor the properties of materials to enhance their radiation resistance. Magnesium aluminate spinel is an obvious choice for such a study, because it is known to resist radiation damage when irradiated with fast neutrons or energetic ions. Recent work has shown, for the first time, that MgAl2O4 can be amorphized at cryogenic temperatures following ion irradiation. Electron diffraction patterns, obtained after irradiating spinel with 400 keV Xe2+ at 100 K to various doses upto 25 dpa, show that the first-order reflections decrease in intensity and become extinct with increasing dose. If the dose is increased further, the material becomes amorphous. We have performed a systematic study of this phase transformation by obtaining the diffraction patterns, and measuring the Young's modulus and nanohardness of the irradiated layer.
Lorentz microscopy observation of vortex dynamics due to transport current
Authors: Yoshida T. , Kasai H. , Bonevich J.E. , Matsuda T. , Tonomura A.
Published: June 2020

At present, Lorentz microscopy is the only one method to visualize individual vortices in superconductors and observe their motion in real time. Using this technique, we have investigated the fascinating vortex dynamics in superconductors, niobium and BSCCO. And recently we applied it to investigate current driven vortex motion.

The vortices are driven by the Lorentz force due to the transport current, and begin to move. This couses the vortex to dissipate the energy i.e., causes the resistive state in the superconductor. Therefore to clarify the vortex motion is important especially in the relation with vortex pinning.

The sample we examined was niobium thin film, which was single-crystallized by annealing and thinned by chemical etching. It was put in the low temperature specimen stage specially developed for the vortex observation, which was installed in 350 kV FE-TEM based Hitachi H-9000.

We observed current driven vortex motion in the temperature (T) range from 4.5 K to Tc = 9.25 K and in a (externally applied) magnetic field (B) up to 100 Gauss.
Superconductivity and observation of ordered structures in deintercalated LixNbO2
Authors: Fendorf M. , Rzeznik M.A. , Stacy A.M.
Published: June 2020

The prevalence of layered structures among the copper oxide superconductors has led us to search for new oxide superconductors with anisotropic structures to evaluate the relationship between structural anisotropy and superconductivity. Because of its layered structure, we identified the dichalcogenide LiNbO2 as a promising candidate for further study. The Nb oxidation state can be readily altered by deintercalation of Li, and we have reported magnetic measurements showing that the resulting LixNbO2 (x<l) is a superconductor with transition temperature Tc=5.5K. Interestingly it is the Meisner fraction rather than Tc, which changes as x is varied in this compound. This suggests that as a result of deintercalation, the material separates into two distinct phases, one superconducting and one non-superconducting, although powder x-ray diffraction shows no clear evidence of differences between LiNbO2 and deintercalated material. This type of behavior is often associated with the transition to the superconducting state as the composition is varied in transition metal oxides.
TEM phase transformation study of (VO)2P2O7 catalyst
Authors: Li Z. G. , Torardi C. C. , Horowitz H. S.
Published: June 2020

(VO)2P2O7 (VPO) is known to act as a heterogeneous catalyst in the oxidation of n-butane to maleic anhydride. DuPont has developed a new circulating fluid bed process for this reaction, and first commercial plant using this technology is scheduled to start up in early 1996. VPO catalyst is typically formed by transforming the vanadyl hydrogen phosphate precursor (VOHPO4. 1/2H2O) to the vanadyl pyrophosphate active phase. It was the object of the current study to develop a more fundamental understanding of this phase transformation.

Transformation conditions were 500° - 700° C in nitrogen. The hydrated precursors used in this study were in the form of plate-shaped single crystals. The crystallographic convention is given in Table 1. Microstructural and morphological changes associated with the phase transformation were studied at scales ranging from the mm to the nm range using scanning electron microscopy (Hitachi S-4000) and transmission electron microscopy (JEM 2000FX). Figure la is an SEM showing the corner of a precursor crystal plate with the c axis indicated.
Preparation of fragile catalyst materials for TEM
Authors: More K.L. , Coffey D.W. , Geer T.S.
Published: June 2020

A novel specimen preparation technique for transmission electron microscopy (TEM) has been developed which allows for the preservation of constituent placement within a variety of diesel and automotive catalyst materials. The standard preparation method for imaging catalyst particles and washcoat constituents has been to use powders scraped from the substrate surface. However, while limited imaging of fine scale structures is possible on clean specimens using this method, all cross-sectional spatial information is lost. Thus, scraped powder specimens cannot be used to directly image surface effects in the TEM or to view large areas of "intact" material in these catalyst systems. Also, for many microscopy investigations such as electron energy loss spectroscopy and high resolution imaging, powders can be too thick. Other preparation techniques have also been used, for example ultramicrotomy and model systems, with some limited success. It is clear that by preparing TEM specimens using this cross-section technique, changes in microstructure to either precious metal particles or washcoat constituents with distance from the exposed surface can be evaluated as a function of aging, engine use, or process modification.
Analysis of fluidized cracking catalysts by Atomic Force Microscopy
Authors: Gould S.A.C. , Occelli M.L.
Published: June 2020

In the United States, five million barrels of oil per day or one third of all processed crude oil is catalytically converted with fluidized catalysts, a process which requires 500 tons of catalyst daily. Given these immense quantities, a small percentage difference in the efficiency of the oil conversion to liquid fuel can result in a savings of many millions of barrels of oil annually. In this study we have used a contact mode atomic force microscope (AFM) to study to topography of a set of fluidized cracking catalysts (FCC) from the μm level down to the atomic. We selected this technique because it is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting a surface which contains numerous pores, something the AFM can well characterize.

We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.
Divergent beam microanalysis studies of bimetallic platinum catalysts supported on γ-AL2O3
Authors: Fryer JR , Huang Z , Stirling D , Webb G.
Published: June 2020

Platinum dispersed on γ-alumina is used as a reforming catalyst to convert linear hydrocarbons to cyclic aromatic products. To improve selectivity and lifetime of the catalyst, other elements are included, and we have studied the distributions of Pt/Re, and Pt/Sn, bimetallic systems on the support both before and after use in octane reforming. Often, one or both of the components are not resolvable by HREM or microanalysis as individual particles because of small size and lack of contrast on the alumina, and divergent beam microanalysis has been used to establish the presence and relationship between the two elements.

In the majority of catalysts the platinum is in the form of small panicles, some of which are large enough to be resolvable in the microscope. The ABT002B microscope with Link windowless Pentafet detector, used in this work, was able to obtain a resolvable signal from particles of 2nm diameter upwards. When the beam was concentrated on to such a particle the signal was at a maximum, and as the beam diameter was diverged - at the same total beam intensity and dead time - the signal decreased as shown in Figure 1.
Effect of oxidation-reduction treatments on the chemisorption ability and reactivity of Pd/SiO2
Authors: Kalakkad Dinesh S. , Datye Abhaya K.
Published: June 2020

Catalytic combustion is known to be the foremost way to oxidize fuels without the simultaneous production of NOx gases. Supported Pd is an excellent catalyst for low temperature catalytic combustion reactions. However, supported metal catalysts are routinely subjected to oxidation - reduction treatments at high temperatures for the sake of initial activation and regeneration after reaction. It has been shown that supported Pd undergoes drastic morphological changes when subjected to oxidation and reduction at high temperatures. These changes include formation of pits, cavities, horse-shoe shaped morphologies and spreading of the palladium oxide on the support followed by redispersion of the reduced metal1. These changes can profoundly affect the catalytic behavior of these catalysts and a thorough understanding of these phenomena is of utmost importance in predicting the behavior of these catalysts under real conditions. However, previous studies reporting these morphological changes have dealt with Pd particles formed by vacuum evaporation onto flat substrates where only plan views of the particles is possible.
Observation of silicon redistribution during TiAl3 formation in aluminum alloy/titanium bilayers
Authors: Alvis Roger , Besser Paul , Sanchez John , Tang Ming
Published: June 2020

Titanium is commonly used as an underlayer to aluminum alloy metal lines in integrated circuit applications, primarily for reliability considerations. The Ti/Al bilayer scheme may exhibit improved electromigration resistance as a combined result of two factors. In the first case, should a void form in Al line, the Ti layer would be capable of carrying a part of the increased current load, effectively shunting the current around the void. The second effect that Ti has is the improvement of the (111) crystallographic texture when compared to Al deposited directly on SiO2 (1). However, the fact that Al and Ti react to form the high resistivity intermetallic TiAl3 at temperatures above 350° C, represents a potentially serious limitation to the practical use of this system. One solution is to alloy the aluminum with silicon, which is known to retard the rate of formation of TiAl3 (2). We propose two mechanisms for the decreased reaction rate involving the diffusion of the Si into the TiAl3 where it acts as a barrier to Al diffusion.
TEM study of Cosi2 formation via annealing of Co-Ti bilayers on Si
Authors: David Theodore N. , Vantomme Andre , Crazier Peter
Published: June 2020

Contact is typically made to source/drain regions of metal-oxide-semiconductor field-effect transistors (MOSFETs) by use of TiSi2 or CoSi2 layers followed by AI(Cu) metal lines. A silicide layer is used to reduce contact resistance. TiSi2 or CoSi2 are chosen for the contact layer because these silicides have low resistivities (~12-15 μΩ-cm for TiSi2 in the C54 phase, and ~10-15 μΩ-cm for CoSi2). CoSi2 has other desirable properties, such as being thermally stable up to >1000°C for surface layers and >1100°C for buried layers, and having a small lattice mismatch with silicon, -1.2% at room temperature. During CoSi2 growth, Co is the diffusing species. Electrode shorts and voids which can arise if Si is the diffusing species are therefore avoided. However, problems can arise due to silicide-Si interface roughness (leading to nonuniformity in film resistance) and thermal instability of the resistance upon further high temperature annealing. These problems can be avoided if the CoSi2 can be grown epitaxially on silicon.
Micropattern analysis of ZnIn2S4 using AFM and TEM
Authors: Martinez L. , Briceño-Valero J. M. , López-Rivera S. A. , Moore K. , Thorthon J. T.
Published: June 2020

Semiconductor ZnIn2S4 is the only member of the II-III2-IV4 family with layer structure. The crystal structure of this semiconductor reported by Lappe et. al. is based upon closed packing of sulfur atoms with octahedral and tetrahedral indium atoms and tetrahedral zinc atoms. Previous studies on this material with high resolution transmission electron microscopy and Ramman spectroscopy demonstrate the existence of challenging problems to be resolved related to its intrinsic nature. There is great interest in this material for possible non-linear optical applications. In the present study Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) have been utilized to reveal crystallographic aspects of this material.

Yellowish, plate-shaped, single crystals of ZnIn2S4 were prepared with the chemical transport method using iodine as a transporting agent. Specimens suitable for electron microscope analysis in the growth direction were prepared by peeling off layers with a piece of tape. For AFM analysis, freshly cleaved surfaces were used.
Microstructure of spin-valve mr sandwiches
Authors: Tang L. , Xiao M. , Laughlin D.E. , Kryder M. H.
Published: June 2020

Giant magnetoresistance ( GMR ) effects in magnetic multilayers with spin-valve structures are under intensive investigation. The GMR effects in spin-valve structures originate from the change in the orientation of magnetization in the successive ferromagnetic layers. Of the various types of spin-valve multilayered structures reported, spin-valve sandwiches, in which one of the two ferromagnetic layers separated by a nonferromagnetic metal layer is constrained through exchange coupling to an adjacent antiferromagnetic layer, are most promising for applications in read heads for high density magnetic recording. This is due to their large MR and high sensitivity in low magnetic fields. Study of the correlation between magnetic/magnetotransport properties and the microstructure of spin-valve sandwiches is crucial for a better understanding of the mechanism of the spin-valve effects and for future MR heads design. Here, we present the results of transmission electron microscopy (TEM) studies of the microstructure of a Ni81Fe19(47Å)\Cu(18Å)\Ni81Fe19(53Å)\FeMn(186Å) spin-valve sandwich.
Microbeam polarization infrared spectroscopy: single fiber discrimination
Authors: Cho Liling , Wetzel David L.
Published: June 2020

FT-IR microspectroscopy of single fiber can produce useful information to distinguish among synthetic fibers. Certain fibers can be readily discriminated on the basis of spectra obtained by this technique. Polarization infrared spectroscopy has been used to measure macromolecular properties such as precipitate crystallinity, polymer film draw ratio, and liquid crystal phase. Measurement of IR dichroism requires light polarized both parallel and perpendicular to a fixed reference direction of the sample. Dichroism may be used to compare and discriminate between different polyester fibers and possibly to establish new groups within a subclass. Four fundamental bands (872, 973,1505 and 1579 cm-1) and two overtone bands (1960 and 3435 cm-1) were chosen because they were relatively free from overlapping bands, and they were weak enough not to be over-absorbing in the spectra of thick, unflattened fibers. During industrial production, the process of drawing can impart many useful properties to a synthetic fiber. When this occurs, molecular chains may become oriented in the long direction of the fiber.
Preparation of successive thin sections of fine oxide particles by an ultramicrotome
Authors: Park G-S. , Shindo D. , Waseda Y. , Yang J-M. , Oikawa T. , Kersker M.
Published: June 2020

A large number of monodispersed fine oxide particles, which are uniform in shape, size and composition, have been developed as ideal advanced materials. Recently, by the newly developed gel-sol method, various shapes of micron-sized monodispersed hematite particles (α-Fe2O3) were produced, such as peanut-type, ellipsoidal and pseudocubic shapes. To understand the growth mechanism of these particles, it is necessary to investigate their internal structures. In this study, in order to analyze three dimensional internal structure of these particles, we have prepared their successive thin sections with an ultramicrotome and carried out HREM study on these successive thin sections.

Monodispersed peanut-type and pseudocubic particles were prepared by the standard procedures of the “gel-sol method. For carrying out ultramicrotomy, these particles were embedded with acrylic resin (methyl methacrylate: n-butyl methacrylate=3:7 or 4:6, benzoyl peroxide 1.5-1.7%) in a gelatin capsule. After trimming with a glass knife, successive thin sections of the particles were obtained by a diamond knife with the optimum slicing condition. The slicing speed and thickness were set to be 0.6 mm/sec and 70 nm, respectively.
Energy-filtered imaging of precipitates in FeCuN alloys
Authors: Rice P.M. , Stoller R.E. , Bentley J.
Published: June 2020

The microstructures of a series of model ferritic alloys are being characterized by transmission electron microscopy (TEM) techniques. The alloys have varying concentrations of Cu (0 to 0.9 wt%), N (5 to 120 appm), and other solutes to allow a systematic study of the effects of various elements on embrittlement. The first step in this process is the characterization of the alloys in their as-received state: solution treated at 775°C for 17 h, quenched in a salt bath at 450°C for 180 s, and subsequently air cooled.

The imaging portion of this initial study is complete; however, several questions about the chemical content of many of the precipitates remain unanswered. The heat treatment described above resulted in extensive precipitation, especially in the high N alloys. It is difficult to distinguish between α” nitride platelets and the ε-carbide platelets which formed in many of the alloys. High-angle tilting is difficult with these ferromagnetic specimens, and the g · R = 0 invisibility criterion previously used for distinguishing the α” nitrides has given ambiguous results.
High-resolution TEM and AEM study in (Au, Tin) thin film on (100) silicon
Authors: Bow J.S. , Hung Y.C. , Kim M.J. , Carpenter R.W. , Kim W.M. , Lee S.K. , Kim S.G.
Published: June 2020

The cross-sectional microstructure of a (Au, TiN) thin film deposited on a (100) Si substrate without further heat treatment was studied by CTEM, HRTEM, and AEM. HTREM was performed in a Topcon 002B microscope with interpretable resolution limit of 0.18 nm, and high spatial AEM was done in a Philips 400ST field emission gun microscope at 100 kV using a Gatan 666 parallel-detection electron energy loss spectrometer. Cross-section specimens of the interface were prepared by traditional polishing and ion milling. Temperatures used in the whole process of TEM specimen preparation were below 100°C and a liquid-nitrogen-cooled cold stage was used in ion milling to prevent interaction between Au and Si.

Ti was co-deposited with Au by sputtering in a nitrogen atmosphere to increase the hardness of the thin Au contact film. Fig. 1a shows the microstructure of the (Au, Ti, N)/Si contact. The features of this microstructure are very similar to the those of pure gold thin films on Si substrates annealed below the Au-Si eutectic temperature (363°C). The thin, white layer was considered to be the original Au/Si interface by Chang et al.
Modification of a TEM for ultra-high-vacuum reflection-EM (UHV-REM) applications
Authors: Hsu Tung , Shih Min-Yi , Latyshev A. V.
Published: June 2020

A JEOL JEM-100C electron microscope was modified by adding a cryogenic UHV specimen holder for studying clean crystal surfaces with the reflection high energy electron diffraction (RHEED) and REM techniques. The Si(111) (l×l) and (7×7) phase transitions have been successfully observed (Fig. 1). Further modification is in progress for better resolution and other functions. Fig. 2.a shows the unmodified specimen holder and the objective lens of the microscope. The cryogenic holder based on the Novosibirsk design is shown in Fig. 2.b. Liquid nitrogen is continuously pumped through the shell of the holder for achieving UHV inside. The tilt/rotation controls and the current for heating of the specimen are fed through the holder. In this modification, the specimen was not placed at the normal position of the lens and therefore is not at the best position for imaging and diffraction.

A new holder is shown in Fig. 2.c. This holder is inserted into the pole piece to place the specimen at the normal position.
Information limit of a 300kV field emission TEM
Authors: Ishikawa I. , Kaneyama K. , Tomita T. , Honda T. , Kersker M.
Published: June 2020

The use of an FEG on a high resolution microscope will increases the spacial and temporal coherence of the microscope due to the improvement in coherence of the electron source. Additionally, the improved energy spread will extend the envelope of the phase contrast transfer well beyond the first zero point at Sherzer focus. Between the Sherzer point and the ultimate point of zero contrast (the information limit) there is useful information for the analysis of high-resolution images. We have already obtained a resolution of 0.194nm and an information limit of 0.14nm by using the 200kV FETEM (JEM-2010F). In the present experiment, we attempted to obtain a higher resolution and information limit by using the 300kV FE TEM (JEM-3000F).

The electron gun is configured with a ZrO/W Shottky emitter which has a small energy spread with a stable emission. The objective lens has a spherical and chromatic aberration of 0.6mm and 1.3mm respectively. The specimen used was gold islands on an amorphous Ge thin film.
Multiple scattering calculations at the oxygen K-edge for SiO2
Authors: Wallis DJ , Brydson R , Gaskell PH
Published: June 2020

Electron Energy Loss Spectroscopy (EELS) in the STEM is potentially a very powerful technique for studying the structure of materials. The Near Edge Structure (NES) in core loss edges carries information about triplet, and higher order correlation functions and under certain conditions is sensitive to long range atomic correlations. However, since the NES contains strong contributions due to multiple elastic scattering, a simple interpretation in terms of atomic structure is not possible. It is therefore necessary to perform some form of modeling to obtain structural information. One approach to modeling NES is Multiple Scattering (MS) theory.

MS calculations have been performed to model the O K-edge ELNES for the α-quartz phase of SiO2 The calculations use a real-space atomic cluster and model the atomic potentials using the Muffin Tin approximation. Effects of the core hole produced upon excitation were accounted for using the (Z+1)* approximation for the excited atom. Energy scales of the calculated data have also been compressed to correct for the energy dependence of the exchange correlation between the photoelectron and the valence electrons which is not accounted for in the calculation.
Development of a multi-user teaching SEM
Authors: Chumbley L. S. , Meyer M. K. , Fredrickson K. , Laabs F. C.
Published: June 2020

The goal of this project is to develop a next-generation laboratory for the teaching of scanning electron microscopy (SEM). Although SEM is one of the most heavily used analytical techniques in the materials field, it has been extremely difficult to teach because of the single-user nature of SEM instruments up to now. Hence, 20 students in a 3-hour weekly SEM laboratory with one machine can hope to get only 10 minutes of hands-on experience per week. To overcome this problem, we have developed a teaching laboratory that makes use of a local area network to provide a large number of students with direct, interactive access to the microscope. Figure 1 is a photograph of the laboratory in operation. This laboratory was field tested Fall semester, 1994 in three separate classes and the students appear enthusiastic about the new method.

The laboratory is based on the JEOL 6100 SEM owned by the Materials Science and Engineering Department. While dated, the microscope does allow a limited number of operational parameters to be controlled through means of an RS-232 serial port by a computer.
Evaluation method for imaging plate resolution by means of phase contrast transfer function
Authors: Oikawa T. , Kosugi H. , Hosokawa F. , Shindo D. , Kersker M.
Published: June 2020

Evaluation of the resolution of the Imaging Plate (IP) has been attempted by some methods. An evaluation method for IP resolution, which is not influenced by hard X-rays at higher accelerating voltages, was proposed previously by the present authors. This method, however, requires truoblesome experimental preperations partly because specially synthesized hematite was used as a specimen, and partly because a special shape of the specimen was used as a standard image. In this paper, a convenient evaluation method which is not infuenced by the specimen shape and image direction, is newly proposed. In this method, phase contrast images of thin amorphous film are used.

Several diffraction rings are obtained by the Fourier transformation of a phase contrast image of thin amorphous film, taken at a large under focus. The rings show the spatial-frequency spectrum corresponding to the phase contrast transfer function (PCTF). The envelope function is obtained by connecting the peak intensities of the rings. The evelope function is offten used for evaluation of the instrument, because the function shows the performance of the electron microscope (EM).
Electron backscatter diffraction a new tool for materials characterization
Authors: Dingley D.J.
Published: June 2020

Electron backscatter diffraction is an experimental technique that provides the investigator with a tool to determine crystallographic data from sub-micron areas of a polycrystalline sample. The first relevant experiments in elctron backscatter diffraction, were conducted by Venables and co-workers followed later by Dingley and co-workers who developed methods of on-line orientation measurement and later phase identification procedures and methods for internal strain measurement.

A specimen is mounted in a scanning electron microscope within which are mounted a phosphor screen positioned vertically and close to the specimen and a low light video camera to view it. The specimen is tilted steeply from the horizontal and oriented to face the phosphor screen. It is normal to enhance the contrast observed in the diffraction pattern using digital background subtraction procedures. A standard arrangement is shown in figure 1.

Electron diffraction occurs within the sample as a natural consequence of the scattering of the electron beam beneath the sample surface to form a divergent source of radiation.
Correlative microscopy techniques for material science
Authors: Hudson J.S.
Published: June 2020

The microscopy center at Clemson University recently invested funds to provide a computer network system that incorporates all of its microscopes. The facility connects SEM, TEM, STM/AFM, Auger Microprobe and the light microscope to Sun workstations equipped with chemical analysis and imaging programs. Images from the network system microscopes can be sent to any of the workstations. I should like to review a few applications of correlative microscopy techniques related to material science; this is a technology that allows the acquisition of multiple data from a given sample. Often a given technique can be augmented by the use of complimentary microscopy technique. Since electron microscopy is subject to interpretation, correlative microscopy methods will prove to be useful in reaching conclusions regarding the image micrographs. Additionally, more than one type of information may be necessary for a given material and this can be found with the different systems of microscopy. In my presentation I will discuss instrumentation and methods by demonstrating advantages and disadvantages of applications as they apply to materials such as polymers, ceramics, microstructures and textiles.
Maximum entropy EM tomography: demonstration of improved resolution with adenovirus
Authors: Skoglund Ulf , Öfverstedt Lars-Göran , Burnett Roger , Bricogne Gérard
Published: June 2020

EMT is a method for three-dimensional (3-D) reconstruction of single objects from electron microscope pictures in a tilt series. The EMT method is general and can be applied to any transparent object, and is not restricted to symmetrical or regularly arranged objects, nor to objects with preferred orientations on a support grid. In its present shape, the EMT method allows reproducible 3-D reconstructions of molecular objects with a resolution in the range of 5 nm. Currently, the EMT method covers the intermediate resolution range where there is no other physical technique available to analyze single molecular complexes.

The recent availability of techniques for high quality automatic data collection from vitrified specimens at low dose promises an improvement of the reproducible resolution as well as considerable expansion of the number of users of the EMT technique. A serious drawback of EMT, however, has been the notoriously low quality of single-object 3-D reconstructions when compared to symmetrized reconstructions.