bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Dopant Type on Polysilicon Grain Growth and Solid Phase Epitaxial Regrowth
Authors: Shlepr MG , Schrantz GA , Rivoli AL , Bajor G
Published: July 2020

A recent process technology to manufacture bipolar junction transistors utilizes polysilicon emitters. Polysilicon is deposited, appropriately doped to form both NPN and PNP transistors, and exposed to temperatures that result in grain growth. Since polysilicon is in contact with Si( 100) at the emitter, base, and collector (Fig. 1), solid phase epitaxial regrowth might also occur. Production runs with this structure occasionally produce transistors with low current gain. High and low gain NPN and PNP transistors were characterized by transmission electron microscopy.

Vertical sections through NPN/PNP transistor arrays were made by the wedge technique, low-angle ion milled to electron-transparency, and viewed at 200 KV. The grain size of the polysilicon on oxide was recorded and estimated. The extent of epitaxial regrowth was quantified for each of the Si (100) contact areas. Convergent Beam Electron Diffraction (CBED) was used to confirm the orientation of the presumed regrown polysilicon.
3-D Observation of Cu Particles Precipitated in Si by High-Angle Hollow-Cone Dark-Field Transmission Electron Microscopy
Authors: Kakibayashi Hiroshi , Nakamura Kuniyasu , Tsuneta Ruriko
Published: July 2020

The performance of electronic devices, such as dynamic random access memories, is degraded by contamination due to impurity atoms as well as crystalline imperfections created during processing. The evaluation of those degradation causes is generally done using an analytical transmission electron microscope. The information obtained, however, is limited to two-dimensional images of the specimen as seen from a single direction. Advanced semiconductor devices with finer-pattern structures are expected to exhibit larger fluctuations in device performance due to the spatial distribution of the faults. A new method has thus been examined to determine the atomic species and to reconstruct three-dimensional (3-D) images of the specimen structure by using high-angle hollow-cone dark-field transmission electron microscopy (HADF-TEM).

A incident angle controller was added to a conventional TEM to control the electron-beam deflection coils. This enables the incident electron beam to be inclined and rotated, providing hollow-cone illumination of the specimen, as shown in Fig. 1.
A Novel Method for Contactless, Non Destructive Investigation of Semi Conductor Structures in the SEM.
Authors: Rau EI , Robinson VNE
Published: July 2020

It is known that scanning a focussed laser beam across the surface of a semi conductor wafer, can produce a photon induced voltage (PIV) at electrically active sites. This technique depends upon the incident photons inducing charge carriers, both electrons and holes, on or just below the surface of the semi conductor. These charge carriers drift through the device until they are captured by a defect, at which stage they accumulate, producing a voltage at the surface. These voltages are only associated with a charge carrier capture site, which means that a voltage build up only occurs at a defect. This PIV technique has been used for contactless imaging of semiconductor wafers, allowing easy identification of electrically active sites such as crystallographic defects, imperfections and inhomogenieties on or just below the surface [1,2].

Nothing in the above mechanism excludes the use of an electron beam to induce charge carriers and produce an electron induced voltage (EIV).
Principles and Possibilities of Backscattered Electron Micro-Tomography in the Scanning Electron Microscope
Authors: Rau E I , Robinson VNE
Published: July 2020

Multi layer structures are widely used in micro electronics devices and visualisation of their sub surface layers is important to understand the nature and properties of these devices. One of the more common methods of sub surface imaging is ion beam milling, in which sections of the overlaying material are removed to reveal sub surface details. Some disadvantages of this technique are that the equipment required is expensive and the technique is destructive. Another technique is to image a device at different accelerating voltages and determine at which voltage a particular feature is first detected. A major disadvantage of this technique is that the underlying layers are always observed partially obscured by the overlaying material. The development of a non destructive technique for three dimensional characterisation of electronic, physical, compositional and/or topological properties of these structures could be useful.

One such technique is micro tomography using the backscattered electron (BSE) signal in the scanning electron microscope SEM [1].
Nucleation and Growth of Aromatic Nitro Compound on Semi-Insulating Silicon Substrates by Organic Molecular Beam Deposition
Authors: Seo KI , Lowe CW
Published: July 2020

From the viewpoint of variety in molecular design, organic molecules have great potential because some of them have large optical nonlinearities. Organic molecules due to a delocalized π-conjugated systems have a number of applications. Since the nitro group is one of the strongest electron-acceptor group, the noncentrosymmetric structures of MNA [2-methyl-4-nitroaniline] and MAP [methyl-(2,4-dinitrophenyl)-aminopropanoate] provide a successful approach for nonlinear optical (NLO) properties.

Heteroepitaxy has become one of the important methods in modern semiconductor technology. In this work the polymeric thin films have grown on crystalline materials by organic molecular beam deposition (OMBD) technique. This provides a highly controlled process of film growth of various organic thin films.

The behaviors of film formation and preliminary results of some properties of mixed MNA-MAP thin films are reported. A surface scientist studying organic interfaces must apply traditional surface science tools with great care. The experimental procedure is followed here in order to examine their morphological features.
Micromagnetic and Microstructure-Property Relationships in Magnetic Recording Media
Authors: Sinclair R , Tang K , McKinlay SE
Published: July 2020

The further development of computer hard disk technology involves ever increasing density of information storage. Current levels of recording are about 1 Gbit per square inch, which will increase by a factor often over the next couple of years. The methodology is well-established: ferromagnetic cobalt alloy thin films (≈20 nm) are sputtered onto an appropriate substrate. Improvement in the magnetic performance (e.g., coercivity, signal-to-noise) requires manipulation of the microstructure by the deposition conditions. Transmission electron microscopy (TEM) is really the only characterization tool which can yield all the necessary information (structural, chemical and magnetic) because of the dimensions involved (e.g., grain sizes of 10-20 nm, with grain boundary segregation an important consideration). This article illustrates some recent contributions to understanding the structure-property-processing combination in this rapidly developing area.

The typical hard disk is made up from an aluminum alloy substrate, a 5-10 micron thick, hard NiP electrodeposited layer, a chromium underlayer, the magnetic Co alloy and a protective thin carbon overcoat.
Electron Holographic Imaging of Magnetic Materials at Nanometer Scale Resolution
Authors: McCartney MR
Published: July 2020

Traditional electron microscopy techniques for imaging magnetic microstructure include out-of-focus Fresnel or Lorentz imaging, Foucault imaging and differential phase contrast (DPC). Off-axis electron holography provides access to both the amplitude and phase of the electron wave which has passed through the sample and therefore can provide direct, quantitative information about the in-plane component of the magnetic induction. The Philips CM200-FEG microscope which was used for the holography described here is equipped with a powerful mini-lens below the specimen enabling 2nm spatial resolution and only a small residual field at the sample. The combination of high coherence and increased magnification enable quantitative mapping of magnetic induction at the nanometer scale.

Electrostatic or magnetic potentials give rise to phase shifts in the holographic interference fringes which can be quantified following reconstruction. In the presence of a magnetic field, the phase equation (for constant composition and neglecting diffraction effects) becomes:
Quantification of Interfacial Segregation by Atom Probe Field Ion Microscopy
Authors: Miller MK
Published: July 2020

The atom probe field ion microscope is a powerful technique for the quantification of solute segregation at internal interfaces due to its ultrahigh spatial resolution. The segregation behavior for all elements is determined by collecting the atoms that originate in a cylinder centered on the boundary region. The method of analysis is dictated by the orientation of the boundary in the field ion specimen. The general case and the two special orientations are shown schematically in Fig. 1. The special case where the unit normal to the interface plane is at 90° to the unit vector parallel to the cylinder of analysis, ϕ = 90°, permits a large number of atoms to be collected but the spatial resolution is defined by the effective diameter of the probe aperture and is typically chosen to be between 1 to 5 nm. The special case where ϕ = 0° provides the highest spatial resolution but only a limited number of atoms are collected from the boundary in each cylinder of analysis.
The Effects of P and Pt on the Microstructure of Co-Cr-P-Pt Thin Film Magnetic Recording Media
Authors: Choi Ju-Hwan , Sung Changmo , Allard Lawrence F , HoShin Kyung
Published: July 2020

Because of their high coercivity, cobalt alloy thin films are among the most popular materials used for ultra-high density longitudinal magnetic recording media. The recording and magnetic properties of the materials are related to their microstructure; in particular, depletion of Co in a grain boundary phase, and physical separation of the grains act to increase coercivity and thus to produce low noise media. We are studying a new alloy system comprising 18 nm thick Co-Cr-P-Pt films (Mr.t ≈ 0.9 memu/cm2), prepared by DC sputtering. A coercivity of 2600 Oe or higher was obtained in these films even when they were deposited without heating the substrate or applying a bias voltage. The effects of P and Pt addition were characterized by high-resolution TEM coupled with energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS). A Hitachi HF-2000 field emission TEM was used to image both low P (≈ 6 at. %) and high P (≈ 12 at. %) samples, and to provide a 1 nm beam for high spatial resolution EDS and EELS.
Quantification of Cu Segregation to Grain Boundaries in an Al - 4 Wt.% Cu Thin Film Using High Resolution X-Ray Mapping
Authors: Carpenter DT , Watanabe M , Barmak K , Williams DB , Smith DA
Published: July 2020

A typical microprocessor chip has several million devices patterned into it and, as fabrication techniques improve, device dimensions continue to shrink. This miniaturization results in a corresponding decrease in the dimensions of the interconnects between devices, causing an increased susceptibility to failure by current-induced mass transport, or electromigration (EM). It is well known that the addition of a small amount of Cu to Al interconnects increases their median time to failure profoundly. Since EM in these films occurs almost exclusively at grain boundaries, the simplest explanation for the role of Cu is that it segregates to the grain boundaries and reduces their diffusivity. Analytical electron microscopy studies have shown that Cu segregates to grain boundaries in Al under the proper conditions, and its concentration was measured using X-ray energy dispersive spectroscopy (EDS), but only a small number of boundaries were measured.In order to determine whether the distribution of Cu affects the resistance of a material to EM damage, it is first necessary to characterize the Cu content of the material as a whole, which requires the analysis of large numbers of boundaries rather than just a few.
A Comparison of Stem-EDX and Auger Analysis of Segregation: The Plaudits and the Pitfalls.
Authors: Tatlock GJ
Published: July 2020

Equilibrium segregation to grain boundaries has been studied for many years, but only recently have the techniques to quantify such segregation at high spatial resolution become widely available. These include, for example, the Auger surface analysis of fractured samples, or the study of boundaries edge-on in a field emission gun STEM equipped with energy dispersive X-ray analysis or electron energy loss spectroscopy. The key question, however, is whether these different techniques yield the same results when applied to a specific set of samples, and this paper reviews some of the successes and problems associated with such studies.

For STEM analysis of grain boundary segregation, several instruments now routinely give probe sizes of ∼1nm. Hence line profiles across grain boundaries at this level of resolution are quite feasible. However a larger probe with greater probe current and better X-ray counting statistics is often more useful, especially if sample drift is a potential problem.
Segregation Measurements in Ferritic Steels Using AES and EDX
Authors: Vatter I A , Titchmarsh JM
Published: July 2020

A quantitative comparison has been made of intergranular segregation in four 9%-Cr ferritic steel alloys, S1-S4 doped, respectively, with 560, 300, 120 and 25ppm P, by both Auger Electron Spectroscopy (AES) and EDX in the analytical electron microscope (FEG-STEM). The strengths, weaknesses, relative accuracies and precision of the two methods were investigated in view of the different equipment, sample preparation, characteristic signals and unrelated assumptions in quantifying the results. No such investigation of ferritic steels has previously been reported, even though they are widely used in engineering components and can be susceptible to embrittlement. Comparative studies have been reported for austenitic alloys.

The steels were solution-treated, tempered at 750°C and aged at 500°C for 100 hours. In-situ impact at low temperature in the VG MA500 AES apparatus caused mixed cleavage and intergranular fracture, the latter increasing with P content. Spectra from up to 80 individual intergranular facets were recorded from each alloy using a 5nA-10KeV beam from an LaB6 electron source under conditions which had been optimised by prior investigation.
STEM Investigation of Segregation and Local Structure at Grain Boundary in Tetragonal Zirconia
Authors: Gu H , Wakai F
Published: July 2020

Y or Ca stabilized tetragonal ZrO2 (TZP) exhibits superplasticity at high temperature, and can also be used as solid electrolytes. Those properties are dictated by structure and chemistry of grain boundaries, which can be controlled by segregation of impurities or additives. The grain boundaries were found either covered by amorphous films or free of the film. Co-segragation of additives and stabilizers has also been observed. To fully understand the correlation between segregation and grain boundary structure, a dedicated STEM (VG HB601) capable of EDX/EELS analysis and phase/Z-contrast imaging is employed to study 3Y-TZP doped with 0.3 and 0.9 mol% SiO2.

Although Y-L lines arc dominated by overlapping Zr-L lines in EDX, Y excess at grain boundaries can still be measured by “spatial difference” which removes Zr signal with a spectrum from the bulk. The co-segregation of Si and Y is also observed (Fig. 1) at many boundaries. Their average excesses arc 5±2 nm−2and 25±10 run−2 respectively, close to 1 monolayer each of SiO2 and Y2O3.
Electron Spectroscopic Investigations of the Solute Drag Like Effect in Fe-C-Mo Alloys
Authors: Menon ESK , Reynolds WT , A.G.Fox
Published: July 2020

The role of various alloying elements on the kinetics of austenite decomposition in steels is well documented. One of the least understood aspects is the ability of some elements like Mo to drastically reduce the kinetics of ferrite (α) growth in austenite (γ).Within specific ranges of transformation temperatures and alloy compositions, the transformation of austenite can cease entirely for extended periods of time (transformation stasis). The phenomenon is quite pronounced in Fe-C-Mo alloys and is clearly evidenced by a horizontal region in the plot of the fraction transformed vs. isothermal reaction time. Based on microstructural and kinetic evidence, the occurrence of the transformation stasis phenomenon has been ascribed to a "solute drag like effect" caused by the segregation of Mo atoms to α : γ boundaries. The proposal that interface chemistry alters the growth kinetics of ferrite is quite difficult to verify as the segregation is expected to be confined to a boundary region less than a nanometer in width.
High Spatial Resolution EBSD Study of Nanosized Epitaxial Particles
Authors: Cosandey F
Published: July 2020

Traditionally, the structure and orientation relationship of individual catalyst particles on various oxide substrates have been studied by transmission electron microscopy. However, the combination of high resolution scanning electron microscopes (HRSEM) equipped with Schottky field emission sources with CCD cameras for recording electron backscatter diffraction (EBSD) paterns, it is now possible to obtain both morpholgy and orientation of individual particles with high spatial resolution. In this paper, we present results on the application of combined EBSD with HRSEM to determine the epitaxial orientation relationship of 80 nm Au particles on TiO2 (110). An evaluation of the spatial resolution limit of EBSD using Monte Carlo simulation of backscattered electron trajectories is also presented.

The TiO2 (110) single crystal surfaces used in this study were prepared in UHV using surface science tools followed by in-situ metallization. After deposition of 15 nm Au at 300K followed by annealing at 800K, the samples were transferred in air to the Field Emission Scanning Electron microscope (LEO 982 Gemini) for high resolution imaging.
Monte Carlo Simulation of Spatial Resolution for Electron Backscattered Diffraction (EBSD) with Application to Two-Phase Materials
Authors: Ren S X , Kenik E A , Alexander K B
Published: July 2020

The study of texture and grain boundary misorientation in multiphase materials has been greatly benefited from the recent automation of the electron back-scattered diffraction (EBSD) technique. With this technique, each phase in a multiphase material can be individually sampled and analyzed. This is of great significance and interest in the study of thin films, inclusions and multiphase alloys. Spatial resolution, which depends on experimental conditions such as beam energy and specimen tilt, and the material being studied, is critical in order to determine the orientation of different phases in multiphase materials.

The Monte Carlo (MC) method has been effectively used to investigate spatial resolution in single phase materials. In this paper, the MC simulation is modified and applied to two-phase geometries. For a bulk two phase (Al/Au) specimen, the coordinate system was defined such that the x-axis was normal to the electron beam and the interface, y-axis parallel to the interface and coplanar to the beam direction, and z-axis perpendicular to the specimen surface which was tilted 70°, as shown in Fig. 1.
REM Studies of Surface Dynamics on Si Surfaces
Authors: Yagi K , Aoki K , Minoda H , Tanishiro Y , Tamura H , Suzuki T
Published: July 2020

Recent developments in techniques of real space observations of surfaces are notable. In them reflection electron microscopy (REM) is a unique technique where in-situ real time observations of wide areas of surfaces are possible. In the present paper recent studies of surface dynamic processes on Si surfaces are reviewed. Observed dynamic processes are adsorption induced successive phase transitions, adsorbate induced facet formations and step rearrangements induced by a reversal of specimen heating current direction(so called current effect) and by a reversal of the sign of the surface strain(strain effects).

Figure 1 reproduces a series of REM images and RHEED patterns taken during successive phase transition induced by Au deposition on a clean Si(lll) surface at 780°C[l]. (a) shows a REM image taken before Au deposition. Line images with zigzag in shape are atomic steps on the surface. The surface steps up to the right as indicated by a step mark. The corresponding RHEED pattern in (b) shows that the surface has the 7×7 structure.
In Situ REM Observation of Step Dynamics on Silicon Surfaces
Authors: Latyshev AV , Yagi K
Published: July 2020

Clear understanding of the structural and morphological transformations on the crystal surfaces can only be extracted from considerations of the dynamical properties of surface evolution. So ultra high vacuum reflection electron microscopy (UHV REM) has been applied to in situ studies of step behaviors on the silicon surfaces during various treatments. Dependence of the surface morphology on the number of parameters is reviewed with new results. Special attention is paid to influence of the electromigration phenomena and strain fields on structural evolution of the surfaces during sublimation, phase transition and epitaxial growth. The stability of the atomic step distributions is discussed in the frame of kinetical morphological transitions on silicon surfaces during DC heating of studied crystal [1].

The step motion during sublimation shows a strong influence of stress fields on the step configurations [2]. The importance of surface stress is obvious because in equilibrium conditions there is a residual stress on the surface due to existence of broken bonds.
In-Situ UHV TEM Investigations of the Initial Stages of Cu(001) Oxidation
Authors: Yang J C , Yeadon M , Kolasa B , Gibson J M
Published: July 2020

We studied the beginning oxidation stage of a model metal system by in-situ transmission electron microscopy (TEM) in order to gain insights into the initial kinetics of oxidation. In-situ TEM experiments can distinguish between nucleation and growth since individual oxide islands are imaged. We chose to investigate Cu, since it is a simple face-centered cubic metal. Also, Cu is a highly promising metal interconnect material because of its low resistivity and good electromigration properties as compared to Al.

Single crystal -1000Å 99.999% purity copper films were grown on irradiated NaCl in an UHV e-beam evaporator system. The free-standing copper film was placed on a specially designed holder, which permits resistive heating of the sample. The microscope used for this experiment is a modified ultra-high vacuum, with base pressure of 10−9 torr, JEOL200CX, operated at l00kV. To remove the native oxide formed during exposure in air, the Cu film was annealed at ∼350°C
Domain Dynamics in Ferroelectric Thin Films Via In-SituTEM Analysis
Authors: Lin Xiwei , Dravid VP , Auciello O , Bjormander C , Foster CM
Published: July 2020

Due to spatial constraints and small dimensions (<1 μm), the ferroelectric domain statics and dynamics in thin films can be significantly different from their bulk counterparts. Further, it has been recognized that electrode-film interfaces play a key role in the fatigue and retention phenomena in the thinfilms for ferroelectric memory applications, which are closely associated with barrier formation and charged defects trapped at various interfaces including the domain boundaries. Thus, it is imperative to utilize in-situ TEM to directly observe the domain switching at a length-scale which is essential (i.e. 1-10nm) for better understanding of the domain dynamics and their interactions with microstructure in thin filmferroelectrics.

We have successfully carried out in-situ TEM observations of domain dynamics in Pb(Zr.5Ti.5)O3 (PZT) thin films using PZT-based capacitor structures. The capacitors were produced by growing PZT layers (∼550 nm thick) on SrRuO3 bottom electrode layers (∼100 nm thick) on (001) SrTiO3 substrates using MOCVD. The top electrode consisted of an ∼200 nm silver layer.
Hydrogen-Induced Phase Separation of Palladium-Rhodium Alloys Using an Environmental Cell TEM
Authors: Teter DF , Field RD , Thoma DJ
Published: July 2020

The palladium-rhodium system has been extensively studied for its hydrogen absorption characteristics. However, the phase diagram of the palladium-rhodium system has not been conclusively determined below 800 K. Shield and Williams have experimentally determined the incoherent miscibility gap in Pd-Rh alloys using electrical resistivity studies, however the coherent miscibility gap and spinodal have not been determined. Recently work by Noh and Flanagan has suggested that hydrogen enhances metal atom mobility and may increase the kinetics of phase separation in Pd-Rh alloys. Field and Thoma found that hydrogen causes a Pd-10%Rh alloy to decompose during an in situhydrogen charging experiment in an environmental cell TEM. According to the calculations by Gonis et al. of the miscibility gap for the palladium-rhodium system, the Pd-10%Rh alloy may be within the chemical spinodal at room temperature.

In this work, two palladium-rhodium compositions were investigated. The first was a Pd-10 at.% Rh alloy produced by melt-spinning, and the second was a Pd-30at.

%Rh alloy which had been arc-melted and cold rolled followed by an annealing treatment to homogenize the material. TEM specimens were prepared by punching 3 mm disks from the material.
Development of an In-Situ Nanoindentation Specimen Holder for the High Voltage Electron Microscope
Authors: Wall MA , Dahmen U
Published: July 2020

Progress on the development of an in-situ nanoindentation specimen holder for the Kratos 1.5MeV HVEM located at the National Center for Electron Microscopy, Berkeley, CA, USA, is reported. There is currently considerable work being reported on the mechanical properties (i.e., hardness, delamination, wear, etc.) of single and multicomponent thin films, nanoclusters and fibers by techniques such as nanoindenting, ref. [1] are recent examples. However, with all of these tests there has not been direct, unambiguous observation of the response or evolution of the microstructure. With many of these reports, there has been little “post-mortem” TEM characterization and there has been no real attempts to simulate these dynamically in the TEM. For the case of nano-testing of the materials the interaction volumes are often on the scale of the natural sampling volume of the HVEM. It seems natural that post-mortem and in-situ TEM characterization techniques be applied.
Microhotplate Chemical Vapor Deposition and in the Environmental SEM Chamber
Authors: Wight S A , Cavicchi R E , Nystrom M J , DiMeo F
Published: July 2020

Metal oxide films are are an emerging sensing technology for the identification of gas phase species. Metalorganic chemical vapor deposition (MOCVD) on microhotplate structures provides a method of fabricating gas sensing layers in self-patterned structures. Investigation of the morphological characteristics of film growth is normally not possible inside a MOCVD reactor, especially the nucleation phase and subsequent deposition of a continuous film. The environmental scanning electron microscope (ESEM) operates at a pressure range of 133-666 Pa (1-5 Torr) which is similar to the growth condition normally used for oxide film MOCVD on microhotplates. Our results show that microhotplate MOCVD can be monitored in situby secondary electron and backscattered electron imaging in the ESEM.

The microhotplate chemical sensor devices employed in this work are mounted in conventional 40 pin packages which provide separate electrical connections to each of the four micromachined heater and contact structures.
In Situ HREm of Reactions at Interfaces
Authors: Sinclair R , Itoh T , Lee H J , Kwon K W
Published: July 2020

Reactions at solid-solid interfaces are important both scientifically and technologically. Firstly, there is quite a wide variety of possibilities. Materials can react with one another, forming equilibrium, meta-stable or even amorphous phases. The interface can provide a means to promote phase reactions kinetically, in an analogous manner to catalysis. Even when the materials are mutually compatible chemically, the interface topography and atomic structure can evolve over the course of time. From the practical point-of-view, changes in the interface chemistry and structure can profoundly alter the physical properties. This is especially notable in thin film technology, whereby the interfaces constitute a signigicant proportion of the whole device. In this article, contributions to understanding this field are illustrated through application of in situ and high-resolution electron microscopy (HREM).

Basic studies of metal-semicoductor interfacial reactions have been successfully carried out for a number of years. of increasing importance in microelectronics is the stability of layers which prevent chemical interaction, namely the diffusion barriers.
HREM Analysis of TiB2 - Ti3B4 Precipitates Grown in-Situin TiAl
Authors: Inkson BJ , Rühle M
Published: July 2020

TiAl alloys are being developed for future use as lightweight, high strength structural materials for the aerospace and automotive industries. The growth of titanium borides in-situ in a TiAl melt can lead to a variety of structures, such as TiB (Bf and B27 structures) and TiB2, depending on the Ti/Al ratio in the melt, and on the presence of further alloying additions [1,2]. The morphologies of the boride particles can be significantly altered if they grow coupled with other boride or intermetallic phases [2-4]. Since the morphology and distribution of the borides with the intermetallic matrix can significantly affect their effectiveness as creep reinforcements, the structures and growth mechanisms of these composites need to be quantified at the atomic scale.

In a Ti-45.5at.%Al-1.6at.%Fe-l.lat.%V-0.7at.%B alloy know to contain TiB2 precipitates [2,3], the morphology of the boride particles have been investigated using HREM. The Stuttgart JEOL-ARM, operated at 1250kV using the side-entry pole-piece with 0.12nm point resolution, enables the distinction between individual boron and titanium columns in the titanium borides to be achieved for the first time.
Chemically Clean Planar Interface Synthesis: Substrate Surface and Interface Cross Section Microscopy
Authors: Xu J , Cox MJ , Kim MJ
Published: July 2020

An ultra high vacuum (UHV) planar interface unit has been constructed to study the effect of interface/boundary structure and chemistry on properties. We report here initial observations of substrate morphology and chemistry prior to bonding and resulting interface morphology obtained using austenitic stainless steel.

To synthesize chemically clean planar interfaces by diffusion bonding, the substrate must be macroscopically and microscopically flat and chemically clean. Macro-flatness, necessary for bonding to occur over large areas, was ensured by conventional mechanical polishing and lapping. Substrate surfaces were cleaned by a broad (3cm) 500 eV ion beam (Ar or Xe) at 15° incidence. The resulting changes in substrate near-atomic-scale roughness and chemistry were analyzed using Auger spectroscopy (AES) and Atomic Force Microscopy (AFM). Before ion beam cleaning, the sub-strates exhibited high oxygen and carbon contamination (Fig la). Both Xe and Ar ion cleaning reduced these values; the result for 5 minutes Ar cleaning is shown in Fig lb.
Subnanometer electron probes and their capabilities for internal interface characterization
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Lakner H
Published: July 2020

Internal interfaces in materials like e.g. semiconductor heterostructures get more and more interest not only under aspects of basic research but as well under aspects of new electronic and optoelectronic devices. The interface properties often govern the device performance. Thus, the evaluation of individual heterointerfaces with respect to chemical composition and crystal structure requires characterisation techniques which offer the necessary high spatial resolution. The fine focused electron probe (< 0.3 nm at 100 keV) in a field-emission STEM (Scanning Transmission Electron Microscope) allows the application of special imaging and analytical techniques to cross-sectional specimens of semiconductor heterostructures. Qualitative information on the chemical composition is provided by atomic number (Z) contrast imaging with atomic resolution. The same fine probe can be used to analyse subnanometer areas by both spectroscopic and diffraction techniques. Quantitative compositional information is provided by electron energy-loss spectroscopy (EELS) which allows the detection of concentrations of specific elements.
Chemistry and Bonding at {222}Mgo/Cu Heterophase Interfaces
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Müller D A , Shashkov D A , Benedek R , Yang L H , Seidman D N , Silcox J
Published: July 2020

Adhesion at ceramic/metal (C/M) interfaces often controls the macroscopic behavior of materials containing metallic and ceramic phases, and experimental studies of bonding at C/M interfaces have recently been reported. Electron energy loss spectroscopy (EELS) offers unique opportunities to examine bonding at interfaces on an atomic scale. The EELS near edge fine structure is sensitive to local atomic arrangements and thus can be used as a coordination fingerprint. Much more can be done, however, by analyzing the connection between the EELS fine structure, the underlying local electronic structure and the cohesive energy of an interface to gain a deeper understanding of the nature of the adhesion at the interface.

In this work, we apply high spatial-resolution EELS instrument to study {222} MgO/Cu interfaces produced by internal oxidation. We determine interfacial chemistry of this interface with subnanometer resolution (Fig. 1) and use EELS to directly measure the electronic states pertaining to the interface
Combined Spectroscopy and STM Studies of (-Cu-O-) Strings on the Ag(110) Surface
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Matsumoto Yuji , Sakamoto Kazuyuki , Suto Shozo , An KS , TakayaFujita  , Kakizaki Akito , Tanaka Ken-ichi
Published: July 2020

It has been found that when Cu atoms are deposited on a p(2×l)-O Ag(ll0) surface, a (2×2)p2mg LEED pattern appears. The STM image has proved that zig-zag (-Cu-O-) strings grow along the [110] direction on Ag(ll0) (Fig. I)1, where a chemical reaction of (-Ag-O-) + Cu => (-Cu-O-) + Ag take place. The (-Cu-O-) strings grown on a Ag(l10) surface shows a unique reversible reaction given by an equation of (Cu)6+O2⇄ (-Cu-O-) at 570K. In this paper, we studied the bond property, the growth mechanism and electric structure of the (-Cu-O-) strings on Ag(ll0) by using XPS, HREELS and ARUPS as well as STM.

As increasing the deposition of Cu atoms on a p(2×l)-O Ag(l10) surface, the O(ls) peak in the XPS shifted from 528.2 eV to 529.9 eV(Fig. 2a). An energy loss peak at 41meV being assignable to (Ag-O) bond disappeared and a new loss peak concomitantly appeared at 35 meV in the HREELS (Fig. 2b).
Quantitative Characterization of Grain Boundary Films In Si3n4 by Eels and Z-Contrast Imaging
Authors: Gu H
Published: July 2020

High temperature mechanical properties of structural ceramics Si3N4 are controlled by ∼1 nm thick silicate amorphous films covering all grain boundaries. The composition of the film dictates the equilibrium film thickness resulted from a force balance at grain boundary. Many efforts arc brought to alter film chemistry and thickness, and this system offers ideal model materials to understand grain boundary and property relationship. Using a dedicated STEM (VG HB601) with high spatial resolution EELS analysis and high resolution Z-contrast imaging, various novel quantification data of the grain boundary in Si3N4 can be obtained. The methods described here can also be applied to other types of grain boundaries.

EELS profiling was performed to acquire a full spectrum from each position at a lateral increment of 1Å across a boundary in a pure Si3N4 sample with only SiO2 impurities from surface oxidation. It gives directly elemental distributions near the boundary such as Si, N and O profiles shown in Fig. 1.
Plutonium Alteration Phases from Vapor Hydration of Lanthanide Borosilicate Glass for Weapons Material Disposition: a TEM Study
Authors: Fortner J A , Mertz C J , Chamberlain D C , Bates J K
Published: July 2020

A lanthanide borosilicate glass, also known as LaBS glass, is being considered for the disposition of surplus weapons plutonium and plutonium residues. The LaBS glass, based upon Löffler-type glasses, is chemically durable and can dissolve substantial amounts of plutonium as well as the neutron absorbers gadolinium and hafnium [1]. Samples of a prototype LaBS glass composition containing 10 wt. % plutonium were subjected to water vapor at 200 °C for periods of 14 to 56 days. The Argonne Vapor Hydration Test Procedure was followed [2]. This test, while not designed to replicate specific conditions that may be found in a potential geologic repository (e.g., Yucca Mountain), has been shown to accelerate alteration phase formation that is usually observed in low-temperature tests over extended time periods [2]. The surfaces of the glass samples, along with alteration phases, were examined with a transmission electron microscope (TEM) to determine the characteristic alteration products.
Digital Moiré Analysis of Interface Dislocation Structure Between S-Phase (Al2CuMg) and Al-Based Matrix
Authors: Radmilovic V , Ratkovic S , Dahmen U
Published: July 2020

Using the moiré technique or the related geometrical phase technique [1,2], lattice displacement fields can be derived from high resolution micrographs by comparison with an undistorted reference lattice. A moiré image gives a magnified view of the distortions in a high resolution image, whether they are due to a distortion of the crystal lattice or result from imaging artifacts. The magnification of a moiré image is determined by the choice of the reference lattice. The closer the reference lattice is to the average lattice period in a high resolution image, the larger the magnification. To first order, both rotations and extensions of the lattice are magnified by the same factor g/Δg, where Δg is the difference between the image lattice and the reference lattice [1]. When the moiré technique is applied to interfaces, care must be taken interpret only patterns from corresponding sets of lattice planes. Thus, the technique gives a good representation of the distortions around a precipitate, but the interpretation of the moiré pattern inside a precipitate or across an interface must be made with caution.
Microstructure of Grain Boundary Junctions in Bicrystal High-Tc Superconductor SQUIDs and its Relation with the Device Noise
Authors: Huang Y , Lee L , Teepe M , Merkle K L , Char K
Published: July 2020

Superconductor Quantum Interference Devices (SQUIDs), because of their extreme sensitivity to magnetic fields and radiation, have found important applications in biomagnetism, non-destructive evaluation and geophysics. One problem in the application of high-Tc SQUIDs is their noise performance. Recently, considerable progress has been made in reducing the noise. To understand the underlying mechanism, it is important to identify the microstructural origin of the junction noise.

In this work actual SQUIDs of good and poor noise performance are studied and compared by TEM. The devices were made by epitaxially growing YBa2Cu3O7-x (YBCO) films using laser ablation on 24° SrTiO3 bi-crystal substrates. The TEM samples were prepared by polishing and ion milling. The TEM observation was performed on a JEOL EM-4000EXII and a Hitachi H-9000 microscope.

Observation shows that the YBCO films and the grain boundary junctions (GB J) in the low-noise devices are in good quality. The microstructure of the films and the boundaries in the films are shown in fig. 1 and 2.
Electron Microscopy Study of Stoichiometric and Non-Stoichiometric Titania
Authors: I.G. Solórzano , T. Kotani , H.L. Tuller , J.B. Van der Sande
Published: July 2020

It is currently well recognized that oxides are able to accommodate deviations from stoichiometry (1) and great advances in this understanding have been achieved by using transmission electron microscopy (TEM), particularly through lattice imaging and electron diffraction techniques (2). The physical properties of non-stoichiometric oxides are strongly influenced by their exact composition and for this reason they represent a class of materials with increasing and novel properties that are put to use in, for example, oxygen sensors and high-Tc superconductors. On the other hand, in electroceramic materials, such as TiO2, grain boundary structure and chemistry are important to be characterized in detail since these variables are responsible for the electric activity.

Rutile (TiO2) can accommodate relatively large deviations from stoichiometry (TiOx with 2.0≥x≤ 1.75) by the crystallographic shear (CS) mechanism (1). The formation of CS planes is effectively a two-step process which involves the ordering of oxygen vacancies on a crystallographic plane and on their elimination by a shear of the lattice.
Structure, Composition and Stability of Heterophase Boundaries
Authors: Rühle M , Wagner T , Bernath S , Plitzko J , Scheu C , Liedtke A
Published: July 2020

Heterophase boundaries play an important role in advanced materials since those materials often comprise different components. The properties of the materials depend strongly on the properties of the interface between the components. Thus, it is important to investigate the stability of the microstructure with respect to annealing at elevated temperatures. In this paper results will be presented on the structure and composition of the interfaces between Cu and (α -Al2O3. The interfaces were processed either by growing a thin Cu overlayer on α- Al2O3 in a molecular beam epitaxy (MBE) system or by diffusion bonding bulk crystals of the two constituents in an UHV chamber. To improve the adhesion of Cu to α -Al2O3 ultrathin Ti interlayers were deposited between Cu and α - Al2O3.

Interfaces were characterized by different transmission electron microscopy (TEM) techniques. Quantitative high-resolution electron microscopy (QHRTEM) allows the determination of the structure (coordinates of atoms) while analytical electron microscopy (AEM) allows the determination of the composition with high spatial resolution.
HRTEM Analysis of Defect Structures in AIN Thin Films
Authors: R. Heffelfinger Jason , F. McCarty Kevin , L. Medlin Douglas
Published: July 2020

HRTEM analysis and conventional TEM techniques were used to determine the nature and density of defects in AIN thin films grown by Molecular Beam Epitaxy (MBE). Extended defects, which act as phonon scattering sites, are detrimental to the thermal properties for which AIN is sought. [1] Previous research on defect structures in AIN has focused primarily on bulk materials. [2-5] This investigation extends previous studies by concentrating on defects native to AIN thin films.

The thin films for this study were grown by MBE onto annealed Al2O3 (corundum structure) substrates with a nominal (0001) surface orientation. The steps and structure of such (0001) Al2O3 surfaces have been previously characterized. [6] Films with thicknesses of 50 to 120 nm were grown at substrate temperatures between 700°C and 900°C. An RF driven source for atomic nitrogen and an aluminum effusion cell were used to generate deposition fluxes. TEM samples were prepared in plan-view and cross-section using conventional dimpling and ion milling techniques.
Complementary Use of APFIM and TEM for a Study of Precipitation in a Rapidly Solidified Stainless Steel
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Kelly T F , Wisutmethangoon S , Camus P P , Larson D J , Miller M K
Published: July 2020

Stainless steels are important technologically for a wide range of applications. Though they are attractive for their environmental stability, austenitic versions of these steels are not generally known for their very high strength. We have rapid-solidification-processed many stainless steels by gas atomization and achieved strength improvements of over 50% relative to conventionally-processed stainless steels with concomitant improvement in corrosion and oxidation behavior. These strength improvements are most pronounced when elevated concentrations of oxygen and vanadium are present in the metal and we need to know how these elements affect precipitation in the alloy.

The specimen material (FCC Fe-16%Ni-9%Cr-0.5%Mn-0.2%V-0.0137%N-0.008%O by weight) was prepared by gas atomization and hot extrusion followed by precipitation aging as described elsewhere. We observed the structure in TEM and found 20 nm precipitates on dislocations, Fig. 1a. We did not observe smaller precipitates in the grain interiors using diffraction contrast bright field imaging, however, with weak-beam dark field imaging, Moiré fringe contrast is observed throughout the material, Fig. 1b.
Type 316l Stainless Steels Exhibiting Five-Fold Symmetry Mo-Rich Phase
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Oh Yong-Jun , Ryu Woo-Seog , Hong Jun-Hwa , Kuk Il-Hiun
Published: July 2020

The existence of phases exhibiting five-fold symmetry patterns has recently been reported for conventional heat treated alloys as well as rapidly solidified alloys. The present paper reports initial results on the analysis of a Mo-rich phase in 316L stainless steel which exhibits this symmetry. The formation and growth of this Mo-rich phase were investigated as a function of aging time. In addition, the effect of nitrogen content on the formation of this five-fold phase was also investigated.

The materials investigated were type 316L stainless steels with nitrogen contents of 0.024% and 0.150%. The materials were solution-annealed at 1100 °C for 30 minites followed by an aging treatment at 700 °C for 10–50 hours in a vacuum sealed quartz tube. TEM samples were prepared by conventional twin-jet polishing and carbon replications extracted by use of a bromine-etch.

Irrespective of nitrogen content, the grain boundary phases after 50 hours of aging were totally observed as five different types of precipitates; M23C6 and M6C carbides, intermetallic η and χ phases, and the five-fold symmetry phase.
Microscopical Examination of a Super Austenitic Stainless Steel
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Fourlaris G , Gladman T , Maylin M
Published: July 2020

Stainless steels have significant applications due to their good corrosion resistance. However, for applications in a marine environment, i.e. for certain types of large naval structures, in addition to the good corrosion resistance, other requirements are imposed on the candidate material such as high strength and toughness coupled with suitable magnetic characteristics.

It has been demonstrated in earlier publications that significant improvements in the coercivity, maximum induction and remanence values can be achieved, by using a 2205 type Duplex austenitic -ferritic stainless steel (DSS) instead of the low alloy medium carbon steels currently being used. These improvements are achieved in the as received 2205 material, and after small amounts of cold rolling have been applied, to increase the strength. However, the 2205 type DSS exhibits “ marginal” corrosion protection in a marine environment as well as exhibiting some measurable ferromagnetic response. Therefore, a study has been undertaken to examine the mechanical properties and microstructures obtained in a super austenitic stainless steel of the 254 SMO type.