bluuebunny/crossref_metadata_2025 huggingface dataset:
Fundamental Constants for Quantitative X-Ray Microanalysis
Authors: C Joy David
Published: July 2020

The development of quantitative X-ray microanalysis in the 1950s spurred the need for knowledge of the many parameters which describe the electron interaction, such as the ionization cross-sections, fluorescent yields, the electron stopping power, mass absorption coefficients, and others. Although classical microanalysis, which proceeds by measurements of the unknown specimen against a standard, can eliminate the need to know many of these parameters accurately, much current microanalysis is done on highly inhomogeneous samples for which comparison with a standard is much less useful procedure. The increased use of low beam energies also means that data is now required for L-, and M-lines which previously have been little used. Consequently there is an enhanced need for a reliable and agreed set of data on which to base calculations.

A common misconception is the belief that all of the quantities that are needed must already have been measured by somebody and so it is simply a matter of accessing this data.
Antimony Delta Doping by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy
Authors: Vanfleet RR , Muller D , Gossmann H-J , Silcox J
Published: July 2020

MBE techniques allow the fabrication of exceptionally sharp compositional changes such as delta doped layers in semiconductors. Producing these spatially confined doped layers is critical to many innovative device designs. The spatial confinement of these delta doped structures can be less than the measurement resolution of the currently standard SIMS and RBS techniques. This allows only the upper limits on the layer width to be measured. These SIMS and RBS methods are also inadequate for the two dimensional information desired for future device design and development. More recently developed techniques such as Scanning Capacitance Microscopy and spreading resistance measurement give two dimensional information but have similar spatial resolution issues. The Z-contrast nature of Annular Dark Field (ADF) imaging with the complimentary technique of Electron Energy Loss Spectroscopy (EELS) in the Scanning Transmission Electron Microscope (STEM) shows promise for two dimensional dopant profiling with spatial resolution on the atomic scale.
Comparison of STEM EELS Spectrum Imaging vs EFTEM Spectrum Imaging
Authors: Hunt JA , Kothleitner G , Harmon R
Published: July 2020

Electron energy-loss spectroscopy (EELS) in the transmission electron microscope (TEM) analyzes the energy distribution of the probe electrons after they have lost energy within the sample. The resultant energy-losses are characteristic of elemental, chemical, and dielectric properties and are typically measured in one of two ways. Parallel-detection EELS spectrometers (PEELS) acquire large energy ranges of the energy-loss spectrum simultaneously for rapid acquisition of spectral data at a single area. In contrast, the energy filtering TEM (EFTEM) acquires only a single energy band at once, but does so for thousands or even millions of image pixels simultaneously.

Spectrum imaging (SI) involves acquisition of detailed spectroscopic data sufficient for rigorous analysis at each pixel in a digital image. (Fig. la) A STEM EELS spectrum image “data cube” can be acquired by stepping a focused electron probe to each pixel and filling the spectrum image one spectrum at a time.
Image-Spectroscopy: New Developments and Applications
Authors: Thomas PJ , Midgley PA
Published: July 2020

The ability of modern TEMs to acquire a series of energy filtered images opens up new possibilities in energy loss compositional analysis. In particular, an electron spectroscopic imaging (ESI) series may be treated as a 2-D array of spectra whose resolution is dictated by the step size of the image series, as illustrated in Fig (a). This allows standard spectroscopic analysis techniques to be used on the extracted ‘image-spectra’, such as the removal of plural scattering by deconvolution. Examples of this are given in Fig (b) and (c), which show how Fourier-log and Fourier-ratio deconvolution can be used to recover the single scattering distribution (SSD) from both the low-loss and core-loss regions from a Cr specimen. A pure elemental sample is ideal for testing the validity of such analysis techniques for quantitative compositional mapping, and more details of this method will be published elsewhere. Further, for many simple metal systems, such as steels and alloys, and for simple semiconductors it is possible to model the plasmon contribution using a simple Drude-Lorentz model.
Compositional Phase Mapping using True Colour X-Ray Imaging
Authors: J. Statham Peter
Published: July 2020

In conventional x-ray mapping, energy regions are defined to straddle the N x-ray spectral peaks of interest. At each pixel position in the digital image, counts are recorded from each energy region and thus give rise to N element maps of intensity distributions over the field of view. Fig. 1 shows an example set of x-ray maps from a polished test sample. It is clear from the images that there are circular regions of differing composition but it is not immediately obvious which regions have the same composition. Furthermore, in a real sample, phases are unlikely to appear in such regular patterns so the correlations between maps are in general much more difficult to notice.

It is possible to choose two x-ray maps and generate a 2D scatter plot showing the intensity values in both maps for all pixels in the image.
Energy Filtering Transmission Electron Microscopy of Polymers and Hybrid Materials
Authors: Du Chesne Alexander , Ulrich Ralph , Wiesner Ulrich
Published: July 2020

A topic of growing importance is the nano-structuring of inorganic materials by exploiting interactions with self assembling polymers. One example are multiphase polymers.

Driven by the mixing enthalpy, most polymers phase separate below their critical solution temperature. The components of block copolymers are covalently linked, restricting separation to microscopic length scales. Depending on composition, block copolymers form different equilibrium morphologies representing the energetically most favorable balance between- interfacial area and chain conformation.

Mass thickness contrast of polymers is often weak and conventional TEM can thus fail to characterize the morphology unless selective staining methods exist. This is the case for the poly(isoprene)-b-poly(ethyleneoxide) diblock copolymer system (PI-b-PEO) used as a structure directing agent and to provide solubility (see below). Fig. 1 shows the micro-domain morphology of PI-b-PEO where the rubbery phase is selectively stained with OsO4.

Hybrid materials are obtained by addition of an inorganic precursor to a solution of PI-b-PEO in a "mutual" solvent.
Characterization Of SiOx Smoke Particles by Electron Energy Loss Spectroscopy and Energy-Filtering Imaging
Authors: Dufner DC , Danczyk S , Wooldridge M
Published: July 2020

Combustion synthesis has led to many advances in materials science, in part via the synthesis of powders consisting of particles of nanometer dimensions. Particle morphology is a key concern regarding the powders produced, but also of comparable importance is particle composition. Electron energy loss spectroscopy (EELS) and energy-filtering imaging (EFI) can be used to interrogate the gas-phase combustion synthesis environment for elemental particle composition information. Once established, this diagnostic approach can be used to address control of particle composition and other issues associated with particle formation and growth in flames. The evolution of the particle morphology in a laboratory scale combustion synthesis facility can be examined by passing TEM grids directly through the combustion synthesis flame at various heights above the burner surface, as shown in Fig. la. For the current work, SiOx particle samples are obtained from a SilL/^/FL/Ar flame using a rapid probe insertion technique.
EELS Characterization of Silicon Oxycarbide Glasses
Authors: Cheng SC , Colombo P , Pantano CG
Published: July 2020

Anionic modification of silicate-based glasses with carbon has recently attracted the attention of many research groups due to the beneficial effect on mechanical properties and both thermal and chemical stability. These carbon containing glasses, termed silicon oxycarbide glasses, can be synthesized from various organically modified silica gels or from preceramic polymers after a pyrolysis process in an inert atmosphere. The oxycarbide network is often mixed with a free carbon phase, and so the local environment around C atoms exhibits a complex distribution. In the ideal silicon oxycarbide phase, carbon atoms would be present only in carbidic units (forming only Si-C bonds). The carbon phases and the chemical bonding in the silicon oxycarbide have been investigated by high resolution electron microscopy (HREM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Electron Energy Loss Spectroscopy (EELS) is an important analytical technique that can be used to further characterize the local chemistry and electronic structure of these glasses.
Threshold Energy Effects in Secondary Electron Emission
Authors: Howie A
Published: July 2020

The work function ϕ, the bandgap Eg, the threshold energy level Et, for the inelastic scattering of excited electrons and the threshold energy transfer Ed for the onset of structural ionisation damage are clearly of major significance in various actively developing forms of hot carrier imaging. Two exciting examples here are the ability to image small and dynamic local changes in work function by PEEM and as well as mapping the variations in electronic structure between p and n-type regions of a semiconductor by SE imaging in the SEM. More recently still there have been indications that the SE signal in the ESEM might be sensitive to local changes in bandgap and suggestions that it might be even possible to image spatial variations in pH. It is increasingly clear that if these attractive opportunities are to be efficiently explored and developed, systematic and preferably quantitative observations are needed. Such work requires specimens whose atomic and electronic structure is either fully known beforehand or can be deduced from other signals available in a situation where the physical processes in the microscope are well understood.
Valence Electron EELS Spectroscopy on Nanoparticle Surfaces
Authors: Colliex C , Suenaga K , Kociak M , Stephan O
Published: July 2020

A series of recent experiments, using electron as well as photon probes [1-3], have attracted considerable interest on the importance of surface plasmon modes in nanostructured media such as nanospheres, nanotubes, nanowires, nanopores or nanoholes.

The basic principle for STEM operation had early been recognized to be well suited to the investigation of cases where non penetrating electrons propagate at a given impact parameter from an external surface (along "aloof7 trajectories, using a terminology proposed by Warmack et al. [4]). One of the most spectacular effect is that signals attributed to the excitation of-surface plasmon modes could be detected in vacuum at distances as large as a few tens of nanometers from the outside surface of a specimen, see for instance [5] for the planar geometry and [6], for the spherical one. Most interpretations accounting for the spatial dependence of EELS spectra in the "aloof geometries, rely on models using the bulk dielectric coefficients of the material to describe the induced charges and polarization responsible for the specimen electric field acting on the probe electron and consequently for the measured energy loss.
Microscopy of Metal Oxide Surfaces
Authors: Castell MR , Dudarev SL , Muggelberg C , Briggs GAD , Sutton AP , Goddard DT
Published: July 2020

Widespread application of metal oxides in catalysis, gas sensing, and as substrates for thin film growth has stimulated a strong interest in the atomic and electronic surface structure of these materials. The electronic structure of many metal oxide surfaces is characterised, and complicated from the theoretical modelling point of view, by the presence of strong on-site Coulomb repulsion (strong correlations) between valence electrons localised on the metal ions. Additionally, experimental studies have to deal with the difficulties associated with the electrically insulating nature of many of these oxides. We have overcome these problems through the development of novel experimental and theoretical techniques capable of providing structural and electronic information about strongly correlated insulating metal oxide surfaces.

The surfaces of NiO and CoO were investigated through elevated temperature scanning tunnelling microscopy (STM) thereby overcoming problems of low electrical conductivity of the samples.We show atomically resolved elevated temperature STM images of (001) cobalt and nickel monoxide surfaces obtained under similar conditions which show an order of magnitude difference in the atomic corrugation heights.
Designer Nanostructures Of Catalysts in the Environmental-HREM
Authors: L. Gai Pratibha
Published: July 2020

Major advances in the field of in situ environmental high resolution electron microscopy (EHREM) probe selective oxidation catalysis directly on the atomic scale. Dynamic gas-solid surface interactions are studied in real-time and under realistic reaction conditions to unravel atomic level insights into active sites and structure-property relationships in vital chemical and technological processes [1-3]. The recent developments include a pioneering approach with the controlled environmental cell (ECELL) facilities permanently mounted inside the EHREM [2]. Accessories have been added for simultaneous structural and compositional analyses of the reactor contents in real-time, and using atomic resolution imaging with transmission electron diffraction and parallel electron energy loss spectroscopy (PEELS). We are now developing innovative experimental methods that include very high temperature studies and combining in the same instrument facilities for both EHREM and environmental-SEM (ESEM), (EHREM-ESEM), with attractive possibilities for studying the science of selective oxidation catalysis.

Alkane Catalysis, Chlorofluorocarbons and Nanotubes:

In the domain of transition metal based oxides, discoveries of fundamental mechanisms underlying selective catalyzation have come from EHREM studies.
Stacking-Fault Fringes
Authors: Barry Carter C , Medlin DL , Cohen Dov , Campbell Geoffrey
Published: July 2020

Crystalline interfaces associated with lattice translations such as stacking-faults (SFs) and twin boundaries may be characterized in the transmission electron microscope (TEM) by oscillatory fringe contrast known as SF, or rigid-body-translation, fringes. Such fringe contrast is usually obtained using weak-beam bright-field (BF) or dark-field (DF) conditions with ideally only one reflection, g, excited. The nature of the SF contrast has been explained by dynamical theory of electron diffraction in terms of the Howie-Whelan equations [1]. The fringe contrast arises from an interference caused by a phase shift the diffracted electron beams, undergo upon propagating across the interface. The phase shift, α, is proportional to the projection of the translation vector, R, onto the diffraction vector, g (i.e. α # g.R). The direction of the translation state can be determined explicitly from the SF contrast in a manner analogous to the analysis of dislocation Burgers vector.

An analysis of SF fringes with respect to diffraction theory permits the magnitude of the lattice translation to be evaluated in experimental images.
In-Situ HREM of A Surface Reconstruction of Si Surface With Molten Al at High Temperatures
Authors: Tsukimoto S , Arai S , Miyai H , Saka H
Published: July 2020

Introduction

The morphology of Si surface has much effect on physical and chemical properties of the surface. It is well known that the structure of Si surface can be modified by deposition of metals, and extensive studies have been carried out on the modified surface structures of Si. These studies were carried out on clean surfaces of Si in an ultra-high vacuum (UHV). However recently, it has been shown by Kamino et al.[l] that molten Au atoms remove a surface amorphous layer on the Si surface, making the surface clean even in a non ultra-high vacuum. The present study is an extension to the previous one (Kamino et al.) and Si surfaces modified by-molten Al atoms in a conventional vacuum were observed by means of TEM.

Experimental

The specimen used in this study was a mixture of pure Al particles and Si particles, the latter being prepared by crushing a Si single crystal into pieces.
Novel Xerogel Catalyst Materials for Hydrogenation Reactions and the Role of Atomic Scale Interfaces
Authors: Gai PL , Kourtakis K , Dindi H , Ziemecki S
Published: July 2020

We are developing a new family of heterogeneous catalysts for hydrogenation catalysis. Catalyst synthesis is accomplished using colloidal polymerization chemistry which produce high surface area xerogel catalysts. These xerogels have been synthesized by one-step sol gel chemistry. These catalysts contain ruthenium and modifiers such as gold occluded or incorporated in a titanium oxide matrix. The materials, especially the modified systems exhibit favorable performance in microreactor evaluations for hydrogenation reactions and exhibit high activities. Nanostructural studies have revealed that the materials contain dispersed catalyst clusters which are desirable microstructures for the catalysis since the majority of the atoms are exposed to catalysis and are potentially active sites.

The composition and atomic structure of the xerogel catalysts containing ruthenium and other metals have been examined using our in-house developments of environmental high resolution electron microscopy (EHREM) the atomic scale [1-3] and low voltage high resolution SEM (LVSEM)[4] methods.
Electron Microscopy of Solid- Liquid Interfaces: HREM Observation and EELS Analysis
Authors: Saka H , Arai S , Tsukimoto S , Miyai H , Konno M , Kamino T
Published: July 2020

A solid-liquid interface in the Al–Si system has been observed at near-atomic resolution by in-situ heating experiments inside transmission electron microscopes. Chemical mapping was also attempt to detect distribution of constituent atoms near a solid–hquid interface.

Mixtures of Al particles and Si particles, the diameter of which ranged from 200nm to 800nm, were mounted on a specimen–heating holder developed by Kamino and Saka and examined in a Hitachi H–9000NAR and a Hitachi HF–2000 electron microscope, operated at accelerating voltages of 300 and 200kV, respectively. Heating these specimens above the melting point of pure Al inside the microscopes resulted in the melting of the Al particles. The liquid Al reacted with nearby Si, leading to the formation of Al–Si alloy phase. An interface between solid Si and Al–Si alloy hquid and also an interface between solid Al and Al–Si alloy liquid were observed. The dynamical behaviour was recorded continuously using TV–VTR systems. The distribution of Al and Si was visualized using a Gatan imaging filter GIF analyzer.
High Angular Resolution Measurements Of K Shell X-Ray Emission Created by Electron Channeling in the Analytical Electron Microscope
Authors: J. Zaluzec Nestor
Published: July 2020

Since the original observations by Duncumb in 1962, a number of studies have been conducted on the effects of electron channel on characteristic x-ray emission and microanalysis. Most of the recent studies have concentrated upon using the phenomenon to perform site specific distributions of impurity elements in ordered compounds using the ALCHEMI methodology. Very few studies have attempted to accurately measure the effect as a function of orientation and compare these results to theory. In this study, two dimensional high angular resolution studies of channeling enhance x-ray emission were performed and herein the results are compared to theoretical calculations of Allen etal.

All experimental measurements presented here were conducted on a Philips EM 420T analytical electron microscope. The instrument was operated in the TEM mode, at 120 kV using an LaB6 electron source. The characteristic x-ray emission was measured using an EDAX ultra thin window Si(Li) detector having a FWHM of ∼ 145 eV at Mn Kα.
Field Emission Characteristics of Single Nano-Tips of Amorphous Carbon Grown on Tungsten Mini-Spheres
Authors: Edgcombe C , Valdrè U
Published: July 2020

Introduction

We report here results additional to those presented earlier on single amorphous carbon nano-tips grown by carbon contamination on substrates of well-defined geometry in a scanning electron microscope (SEM). This method offers beneficial accuracy in controlling the properties of the nanoemitters such as length, aspect ratio and positioning on the given substrate.

The work function, emission field, current density, emitting area, solid angle of emission, energy distribution and short and long term stability of these emitters are all of interest. Since the literature does not provide, as far as we know, the work function of contamination-grown amorphous carbon, its value must be determined experimentally, in our case through Fowler-Nordheim (F-N) plots. This quantity and others can be derived once the electric field F at the emitting surface is known. Since the geometry of our emitters is reasonably well known from the fabrication procedure and subsequent electron microscopy, it is possible to find a satisfactory value for F by computation.
High Resolution Measurements of Two Dimensional Dopant Diffusion in Silicon
Authors: Spinella Corrado
Published: July 2020

The development of the very large and ultra large scale integrated technology technology is based on the shrinkage of the lateral dimensions of semiconductors devices to a sub-micron level. Under these conditions the precise control of the total amount of dopant atoms dissolved in the silicon substrate, and of their depth and lateral distribution, become crucial requirements. One of the most promising device characterization technique is that based on transmission electron microscopy (TEM) analysis. Indeed, by means of TEM observations the device morphology can be imaged with a spatial resolution of the order of 0.1 — 0.3 nm; and, after an appropriate sample preparation method, based on selective chemical etch of doped silicon regions, the 2D dopant concentration profiles can be delineated with a resolution of the order of 5nm.

The chemical solution used for this aim consists of a mixture of both nitric and hydrofluoric acid.
In-Situ TEM Studies of the Interaction Between Dislocations in SiGe Heterostructures
Authors: Stach EA , Hull R , Tromp RM , Ross FM , Reuter MC , Bean JC
Published: July 2020

The rate of heteroepitaxial strain relaxation via misfit dislocation introduction is strongly limited by the kinetics of dislocation nucleation, propagation and interaction. Here we describe real-time observations of the interaction between moving threading dislocations and pre-existing interfacial misfit dislocations using in-situ transmission electron microscopy. This was accomplished both during in-situ observations of the heteroepitaxial growth process using a modified ultrahigh vacuum TEM (UHV-TEM) equipped with chemical vapor deposition capabilities, as well as during in-situ anneals of metastable structures grown by molecular beam epitaxy.

In Figure 1, we present our UHV-TEM observations of the epilayer thicknesses and compositions at which dislocation interactions result in blocking of the propagating threading segment, and compare these with the theoretical predictions of Freund and those of Schwarz and Tersoff. Our results show that dislocation blocking can significantly affect the overall rate of strain relaxation in these structures. This is important, as blocked threading segments introduce undesired band gap states into electronic devices and can act as easy diffusion paths for impurities and dopants.
Lighting With GaN: How Can HREM Help To Understand The Iii-Nitride System?
Authors: Kisielowski C , Nelson EC , Song C
Published: July 2020

Nowadays, High Resolution Electron Microscopes are capable to resolve structures on a scale below 100 pm. They can be equipped for Electron Holography in order to detect electric / magnetic fields and for chemical analyses (Electron Energy Loss Spectroscopy & Energy Dispersed X-ray's) that can be performed with a lateral resolution of 0.5 to 1 nm [1]. With the aid of computer sciences it became also possible to quantify local strain. We utilize Philips CM200 and CM300 field emission instruments with attached image filters, the JEOL Atomic Resolution Microscope and specialized software [2] to perform these tasks. On the other hand, a recent highlight in materials sciences is the development a GaN technology that is driven by a fast trial and error approach and aims to revolutionize lighting [3]. It was unavoidable that basic materials properties of the nano-structured thin films are barely understood because of the rapid progress [4].
Detection of Interstitial Molecules in Wide Band Gap Materials Using Cathodoluminescence Microanalysis
Authors: Stevens Kalceff MA
Published: July 2020

Cathodoluminescence (CL) microanalysis (spectroscopy and microscopy) enables both pre-existing and irradiation induced defects in the bulk and surface defect structure of wide band gap materials (i.e. semiconductors and insulators) to be monitored and characterized with high spatial resolution and sensitivity. The local micro-volume of specimen may be selected for investigation by varying the electron beam parameters. CL micro analytical techniques allow the in situ monitoring of electron irradiation induced defects and the investigation of irradiation induced electromigration of mobile charged defect species. Irradiation can result in the formation of defects and /or the transformation of existing defect precursors. CL emissions from a material are usually associated with native and impurity defects of the host lattice, however in special cases CL microanalysis can provide direct or indirect evidence for the presence of interstitial molecular species in a material. Atomic displacements from the normal bonding (i.e. defect free) sites induced by an electron beam can result from either knock-on, or radiolytic processes, depending on the incident electron beam energy.
Horizontal Defects Parallel to the Interface in GaN Pyramids
Authors: Mao Zhigang , McKernan Stuart , Barry Carte C , Yang Wei , A. McPherson Scott
Published: July 2020

The performance of III-V nitride-based microelectronic and optoelectronic devices relates directly to the micro structure of these materials. Selective lateral overgrowth has been exploited to produce GaN heteroepitaxial films with low defect density [1]. Si is a promising substrate due to its low cost, large size, and the potential for the intergration of GaN-based optoelectronic devices with Si-based electronics. It is also possible to produce high-quality GaN material for devices using lateral overgrowth on a Si substrate [2]. At present, only limited information on the defect structure in GaN heteroepitaxial films grown by selective lateral growth is available, especially those grown on Si substrate. Recent work [3] on GaN pyramids grown on (111) Si substrates by this method has shown that in the center, or core, of the GaN pyramid (at and above the window area) dislocations thread through the pyramid nearly perpendicular to the substrate surface and the dislocation density is quite high.
Weak-Beam Thickness-Fringe Contrast Analysis of Defects in GaN Pyramids
Authors: Mao Zhigang , McKeraan Stuart , Barry Carter C , Yang Wei , A. McPherson Scott
Published: July 2020

The possible dislocations and slip systems in the wurtzite structure are the same as in hcp structure [1]. The Burgers vectors of these dislocations are . The dislocations can lie on either the (0001) basal plane or prism planes. The dislocations lie on pyramidal planes. TEM studies have revealed that there are predominately three types of dislocations in a wurtzite GaN epilayer which has not been grown by selective overgrowth (e. g. [2, 3]). The majority of the dislocations are threading dislocations with Burgers vector which appear randomly in the epilayer, they result from the growth errors during the growth process. The other two types of dislocation are halflpops with a [0001] or Burgers vector. The [0001] dislocation half-loop lies on the prism plane and the dislocation half-loop lies on the (0001) basal plane which usually appears near the epilayer/substrate interface.
Chemical Characterization of Semiconductor Defects and Particles on the Wafer Surface by Multiple Microanalysis Techniques
Authors: Uritsky YS , Conti G , Brundle CR , Savoy R , Kinney PD
Published: July 2020

Development of future semiconductor processes and improving existing ones requires a strong capability to identify and eliminate the sources of particle defects. The current industry approach for accomplishing this task is to analyze the particles on the wafer surface. The most commonly used technique for this purpose is SEM with EDX (SEM/EDX). This approach provides information about defect chemistry and morphology, which in turn provides a direct path to the reevaluation of processes and hardware parts needed to determine the root cause of a problem. However, the SEM/EDX has three fundamental limitations: (a) it is a large volume technique and therefore, the sensitivity can be insufficient for sub micron particles and thin patches; (b) there is no chemical bonding information due to poor energy resolution; (c) charging problem for dielectrics. In some cases there is a need to use other techniques to support or substitute the EDX results.
Microanalytical Characterization of Structure and Defects for the Development of Low Temperature Silicon Epitaxial Growth
Authors: Jones KM , Thiesen J
Published: July 2020

The nano-scale dimensions of next generation VLSI and ULSI devices will drive the development of a variety of new processing requirements. Currently device processing conditions from substrate cleaning to thin film deposition require temperatures in the range of 600°C to 1200°C. In order to realize a Si device circuit architecture which integrates Si/Ge structures or the needed super abrupt junctions of buried channel CMOS, low temperature processes must replace those in current production lines. For these processes to be successfully developed and implemented, proper characterization techniques must be used. In the case of epitaxy, cross-sectional TEM is the tool of choice. We will discuss the prominent role that TEM has played in the development of a new Si epitaxy technology. Recently, at the National Renewable Energy Laboratory (NREL), we have shown low temperature, 195°C to 400°C, Si epitaxy via hot-wire chemical vapor deposition- HWCVD. In the past HWCVD has been used to produce amorphous, micro-crystalline, and polycrystalline Si thin films.
Grain Boundary Segregation and Irradiation-Assisted Stress Corrosion Cracking of Stainless Steels
Authors: Kenik EA , Busby JT , Miller MK , Thuvander AM , Was G
Published: July 2020

Irradiation-assisted stress corrosion cracking (IASCC) of irradiated austenitic stainless steels has been attributed to both microchemical (radiation-induced segregation (RIS)) and microstructural (radiation hardening) effects. The flux of radiation-induced point defects to grain boundaries results in the depletion of Cr and Mo and the enrichment of Ni, Si, and P at the boundaries. Similar to the association of stress corrosion cracking with the depletion of Cr and Mo in thermally sensitized stainless steels, IASCC is attributed in part to similar depletion by RIS. However, in specific heats of irradiated stainless steel, “W-shaped” Cr profiles have been observed with localized enrichment of Cr, Mo and P at grain boundaries. It has been show that such profiles arise from pre-existing segregation associated with intermediate rate cooling from elevated temperatures. However, the exact mechanism responsible for the pre-existing segregation has not been identified.

Two commercial heats of stainless steel (304CP and 316CP) were forced air cooled from elevated temperatures (∽1100°C) to produce pre-existing segregation.
Nanoscale Structural Characterization at the Titanium/Sol-Gel/Primer/PETI-5 Interface
Authors: D. Holbery James , M. Fisher Robert
Published: July 2020

Characteristics of the interfacial region between a polymer and substrate are critical to the durability of adhesive-adherend system performance. The High Speed Civil Transport (HSCT) requires structural laminates to be light weight, non-corrosive, environmentally safe, and able to withstand extreme service conditions (Mach 2.4 with in-service temperatures at 177°C, projected life to 120,000 hours). The present work characterizes multi-layer laminates comprised of a Titanium substrate (6A1-4V and 15V-3Cr-3Al-3Sn alloy), a silicate/zirconate sol-gel coating with aminopropyl functionality (nominally 1000 Angstroms), a NASA developed PETI-5 psuedothermoplastic polyimide primer (nominally 1000 Angstroms), and a high toughness, thermo-oxide stable PETI-5 adhesive. Previous studies report the physical effect of aging; therefore, this work aims to measure the nano-mechanical properties of the interface utilizing nano-indentation and AFM, focusing on the accelerated time-dependent changes due to extreme environmental exposure.

Samples were prepared by sectioning each laminate (No Environmental Exposure, 1000 and 2000 Hours at 200°C) in two locations, one section externally exposed to environmental test conditions and the other from the middle of the laminate.
Combined HRTEM and High Spatial Resolution Analysis of Homologous Compounds InMO3(ZNO)m By A 300kv FE-TEM
Authors: Bando Yoshio , Li Chufei , Nakamura Masaki , Kimizuka Nobuo
Published: July 2020

A series of homologous compounds InMO3(ZnO)m (M=In, Fe, Ga and Al, m=integer) has been synthesized successfully by the present authors. From x-ray diffraction, the strutcure is considered to be a layered structure, consisting of InO2  −1-(In-O layer) interleaved with M/ZnmOm−l  1+ (M/Zn-O layer). The space group is assigned to be R3m when m is an odd number, while it is P63/mmc when m is an even number. The distribution of M atoms within the M/Zn-O layers is considered to be random. However, from electron microscopy study, the existence of the modulated structures showing non-integral periodicities has been observed. The high spatial resolution EDS analysis using 0.5 nm electron probe diameter under a 300kV FE-TEM showed that the sinusoidal modulated structure is caused by the ordering of M atoms within the M/Zn-O layers. In the present study, modulated structures of InMO3(ZnO)13, where M atoms consists of two metals such as In and Fe, Ga, Al and Fe are studied by combined use of HRTEM and high spatial resolution EDS analysis using a 300kV FE-TEM.
Electron Spectroscopic Imaging and Diffraction: Ideal Tools for the Characterization of Ceramic Materials
Authors: Mayer J , Plitzko J , Marien J , Krämer S , Gemming T
Published: July 2020

The most widely spread application of energy filtering transmission electron microscopy (EFTEM) is the determination of elemental distributions in analytical investigations. The new EFTEM techniques are based on data acquisition by electron spectroscopic imaging (ESI), which offers the advantage of fast two-dimensional recording of the inner-shell loss intensities. In a more general framework, the new ESI methods and the standard PEELS technique both aim at exploring the same three dimensional data space. This data space is represented by the spatial coordinates x, y and the energy loss ΔE and the resulting intensity distribution I(x,y,ΔE) is the quantity which is evaluated. It is intuitively clear, that acquiring more than just three consecutive ESI images gives us the possibility to get quantitative information about the spectra and the shape of the ionization edge. The information on the EEL spectrum can be extracted from a series of ESI images for each individual pixel or, by integrating over corresponding pixels, for a given image area and can be quantified by applying standard EELS quantification techniques.
Local Density Information From Low Energy-Loss Peels Measurements
Authors: C. Bell David , L. Mired Clark , W. Hobbs Linn
Published: July 2020

It is known that radiation produces microscopic and macroscopic changes in silicas and other silicate glasses that result in densifications of several percent [1], This change in density is matched by a corresponding linear change in refractive index via the Lorentz-Lorenz relation such that where R is the molar polarizablilty, V the molar volume and n the refractive index.- Measurements of neutron irradiated bulk a-Si02 yield an exact correlation between the refractive index and density as shown by Fig. 1 such that dn/dp =185 m3/kg [ 1 ].

Utilizing a VG HB603 STEM fitted with a parallel EELS, measurement of irradiation-induced density changes in silicas were attempted using the 0-100 eV low-loss region of the electron energy-loss spectrum. The dielectric function and refractive index changes were extracted from these data using a modified Kramers-Kronig analysis (Fig. 2).
The Study of Grain Boundaries in Ag-Sheathed Bscco Tapes by Scanning Transmission Electron Microscopy
Authors: Kishida K , Pan Y , Browning ND
Published: July 2020

Highly textured (Bi,Pb)2Sr2Ca2Cu3O10(Bi-2223)/Ag composite tapes have received considerable attention as high-Tc superconducting materials for electric power and high-magnetic-field applications because of their relatively high-critical current densities and their flexibility. In order to improve the performance of these tapes for many commercial applications, it is essential that the mechanisms that limit the critical current density are fully understood. Previous microscopical studies of these tapes have revealed that interfaces such as grain boundaries strongly influence the transport of large currents1. From a morphological point of view, several models have been proposed to describe potential current transport mechanisms. However, as these models consider mainly the large-scale configuration of the boundaries, the underlying mechanism controlling the properties is still unclear. In order to elucidate the exact role of grain boundaries, systematical studies on the effect of the atomic structure as well as any chemistry change that occurs at the interface are required.
Growth and Texture of Polycrystalline SIC on Graphite During Forced flow Thermal Gradient Chemical Vapor Infiltration (FCVI)
Authors: Appiah KA , Wang ZL , Lackey WJ
Published: July 2020

Silicon carbide is a versatile material possessing properties such as a wide energy bandgap, high thermal conductivity, high elastic modulus and high-temperature creep resistance, which enable it to be used in a variety of electronic, optical and structural applications. Chemical vapor infiltration/deposition (CVI/CVD) coupled with the application of a temperature gradient and forced flow of reagents is particularly suited to the production of SiC structural composites due to the benefits of reduced infiltration time and uniform composite density. In this work, the growth and orientation of polycrystalline SiC on graphite during CVI is investigated using TEM and HRTEM.

The composites studied possess a laminated matrix of alternating layers of carbon and SiC which were deposited by alternating the reagent streams from one layer to the next. Specimens for TEM examination were obtained by cutting ∽1 mm thickness slices from the bulk sample with a low speed diamond saw.
Migration of Silicate Liquid Out of Grain Boundaries in Ceramics
Authors: Ravishankar N , Barry Carter C
Published: July 2020

Liquid-Phase Sintering (LPS) is a conventional fabrication route for the densification of alumina and other ceramics. The polycrystalline ceramics processed by LPS contain siliceous phases along the grain boundaries. This wetting of the grain boundaries has a strong dependence on the crystallography of the boundary. The liquid preferentially wets certain orientations while some special boundaries are ‘dry’. The mechanism of dewetting of these boundaries is not well understood. Several approaches have been adopted to study the nature of the liquid-solid interaction at the grain boundaries. In commercial alumina, anorthite is the most commonly found intergranular phase.

Basal twist boundaries in alumina which contain a thin layer of anorthite glass have been investigated in the present study. Pulsed laser deposition has been used to deposit thin films of anorthite glass on optically flat basal sapphire. The substrate-film assembly is then bonded to an optically polished basal sapphire by sintering the assembly at 1650°C for 2h.
Second Difference Electron Energy-Loss Spectroscopy with the Gatan Imaging Filter
Authors: Buck EC
Published: July 2020

The large number of minor elements present in geological specimens and nuclear waste materials, can make TEM/EDS analysis of such samples troublesome. With a parallel detector such as the Gatan PEELS 666, the second difference technique has been shown to be effective at removing the channel-to-channel gain variation [1]. As spectroscopy performed with the Gatan Imaging Filter (GIF200) averages over a 2D array, gain variations are minimal; however, the second-difference technique selectively enhances the high frequency features such as the “white line” absorption edges, particularly of rare earth elements (REE) and transuranics (TRU). The second difference method may thus still have merit with the GIF200. A script was created within the controlling software program (DigitalMicrograph ™) which permitted second difference acquisition [2]. The Spectroscopy Package was also modified with ResEdit and the required values were added to the Global Tags to enable easy application of the second difference routine.
Analytical Electron Microscopy Investigation of Coated 3M Nextel 720™ Fibers
Authors: Nagarajan R , Fox AG , Boakye E , Hay RS
Published: July 2020

An oxidation resistant interfacial layer between the fiber and the matrix is important for prolonged use of ceramic-matrix composites (CMC). The interface layer has to be chemically compatible and stable in high temperature oxidizing environments. At present various oxide based interface layers in CMC are being considered. One candidate is porous interfaces. Zircon has good thermomechanical stability with SiC and mullite, and resists pore coarsening, so it is of interest as a porous interface materials.

Ethanolic zirconia and silica precursors, complexed with polyelectrolytes to form fugitive carbon for porosity were doped with vanadium. These were used to continuously coat the 3M Nextel 720™ alumina-mullite fibers. These fibers were heat-treated in-line in argon at 1000-1300°C, with the aim of finding heat-treatment conditions that would convert the zirconia, silica, and polyelectrolyte into a fine mechanical mixture of zircon and carbon.
TEM Study of Nanocrystalline Ni Films Grown by Dc Magnetron Sputtering
Authors: Mitra R , Chiou WA , Weertman JR , Hoffman R
Published: July 2020

Nanocrystalline bulk Ni processed by inert gas condensation of powders followed by compaction has shown impressive mechanical properties with strength values as high as 50% of the theoretical shear strength. However, the process of warm compaction required for densification often leads to grain growth, and flaws in the microstructure. In this study, thin films of nanocrystalline Ni were processed by magnetron sputtering to bypass the compaction process and achieve a microstructure with very narrow grain size distribution. This paper presents the grain size distribution and other microstructural features of nanocrystalline Ni films.

Ni films were grown on Si and NaCl substrates, using argon plasma generated with the help of a plasma d.c. magnetron source equipped with a Ni target of 99.99% purity. The target power used was 200 W and the argon pressure was maintained at around 6 millitorr during deposition. A pulsed dc negative bias of 0 or 100 V was applied on the Si substrate.
Effect of Pre- And Post-Deposition Heat Treatment on Microstructure and Electrical Properties of ITO Films Deposited on Pet and Glass Substrates
Authors: Dolukhanyan T , Kwon JG , Moon SC , Kang MG , Sung C
Published: July 2020

ITO films on PET in combination with ITO films on glass substrates are extensively used in Touch Panel Displays fabrication. Main properties of interest for these systems are high optical transmittance ∽95%, low resistivity ∽10−3 Ωcm, coupled with uniform and stable sheet resistivity demanded for long term use.

The goal of this investigation is to understand relationship between microstructure and electrical/optical properties of ITO films on PET and glass substrates as a function of pre- and postdeposition annealing parameters.

ITO films of ∽60 nm thick have been deposited by radiofrequency magnetron sputtering. This method can be applied over a wide range of substrate temperatures. This is essential for plastic substrates such as PET. Regions of good and poor conductivity have been identified for TEM analysis and Analytical Electron Microscope (Philips 400 EM), equipped with light element Noran Instrument Energy Dispersive X-ray Spectrometer (EDXS) have been utilized.
TEM And IR Reflectance Studies on Phase Transitions in Thin VOx Films.
Authors: Verheijen MA , Boonekamp EP
Published: July 2020

Vanadium dioxide (VO2 ) exhibits a reversible semiconductor-to-metal phase transition around 341 K. The low temperature monoclinic P21 /c structure transforms into the tetragonal P42 /mnm rutile structure. The associated sharp changes in optical and electrical properties are used in various thin film switching devices. The present paper describes a study on the optical and structural changes during the synthesis of VO2 thin films using Infra-Red (IR) reflectance spectroscopy and Transmission Electron Microscopy (TEM).

The synthesis was derived from a sol-gel process by Guzman et al. Solutions of vanadyl isopropoxide (VO(OC3 H7)3 ) in n-propanol were spin-coated on a Si wafer provided with 300 nm thermal oxide. Subsequently, the wafer was transferred to an oven and heated to 773 K in a reducing H2/N2 atmosphere using a heating rate of 5 K/min. After a variable time (Δt) at 773 K, the samples were cooled down to room temperature.

Figure 1 shows the IR reflectance of thin (∽50 nm) VOx films on oxidised Si at λ,=3 μm and an angle of incidence ϕ of 30°.
TEM Examination on the Microstructure Rearrangement of ECRPVECD Nc-Si Thin Films Caused By Low Temperature Annealing
Authors: Cheng SC , Kalkan AK , Bae SH , Fonash SJ
Published: July 2020

In an earlier report we have shown that the infrared photoluminescence (PL) from nanocrystalline Si films shifts to lower energies with increasing deposition temperature (in the range of 180-340 °C) and with thermal annealing. These films were deposited on Corning 1737 glass substrates using a Plasma-Therm SLR 770 ECR-PECVD system to a thickness of 4500 Å. The redshift of PL correlates well with the narrowing of (111) XRD peak, the redshift of the optical absoiption profile, the increasing conductivity and the decreasing activation energy for conductivity. Therefore, the energy shift of the PL has been considered as the result of variations in bandgap due to variations in crystallite size; i.e., variations in the quantum confinement. For the samples investigated, the PL band peak was found within the extrema of 0.99 to 0.81 eV (at 77 K). These extreme values correspond to the film deposited at 180 °C (0.99 eV PL) and the same film annealed at 600 °C for 72 hours (0.81 eV PL).