Search

Dislocation mediated alignment processes during gold nanoparticle coalescence were studied at low and high temperatures using molecular dynamics simulations and transmission electron microscopy. Particles underwent rigid body rotations immediately following attachment in both low temperature (500 K) simulated coalescence events and low temperature (∼315 K) transmission electron microscopy beam heating experiments. In many low temperature simulations, some degree of misorientation between particles remained after rigid body rotations, which was accommodated by grain boundary dislocation nodes. These dislocations were either sessile and remained at the interface for the duration of the simulation or dissociated and cross-slipped through the adjacent particles, leading to improved co-alignment. Minimal rigid body rotations were observed during or immediately following attachment in high temperature (1100 K) simulations, which is attributed to enhanced diffusion at the particles' interface. However, rotation was eventually induced by {111} slip on planes parallel to the neck groove. These deformation modes led to the formation of single and multi-fold twins whose structures depended on the initial orientation of the particles. The driving force for {111} slip is attributed to high surface stresses near the intersection of low energy {111} facets in the neck region. The details of this twinning process were examined in detail using simulated trajectories, and the results reveal possible mechanisms for the nucleation and propagation of Shockley partials on consecutive planes. Deformation twinning was also observed in-situ using transmission electron microscopy, which resulted in the co-alignment of a set of the particles' {111} planes across their grain boundary and an increase in their dihedral angle. This constitutes the first detailed experimental observation of deformation twinning during nanoparticle coalescence, validating simulation results presented here and elsewhere.

In this study, strontium titanate bicrystals with a twist grain boundary were successfully formed using a spark plasma sintering apparatus. Diffusion bonding was accomplished at high pressure and fast heating, and provides a novel method to form bicrystals at lower temperatures and accelerated time scales compared to more established techniques. Scanning electron microscopy was used to quantitatively evaluate the degree of successful interfacial bonding. Atomic resolution imaging using transmission election microscopy techniques combined with spatially resolved electron energy-loss spectroscopy measurements confirm a clean and atomically abrupt interface free of secondary phases.

This article investigates nanostructures by means of scanning transmission electron microscopy. The electron microscope is uniquely suited to the study of individual nanostructures, allowing differentiation of different structures and properties that is difficult or impossible to do with techniques that provide a spatial average. The present generation of aberration correctors, which correct all aberrations up to third order, makes it possible to obtain sufficient sensitivity to image and spectroscopically analyze single atoms. This article begins with a brief overview of the correction of lens aberration in electron microscopy, followed by several examples of insights into nanomaterials and the atomic origins of their functionality. In particular, it considers semiconductor nanocrystals, semiconductor quantum wires, and nanocatalysts. It also discusses magnetism in gold and silver nanoclusters as well as charge ordering in manganites.

The formation of a pre-silicide layer below Ni1-xPtxSi films is reported with structure and composition distinctly different from previously observed diffusion layers. It was found that during two-step rapid thermal annealing Ni interstitial diffusion can kinetically dominate over the formation of Ni silicide, which results in a metastable pre-silicide layer. Aberration corrected scanning transmission electron microscopy experiments have revealed Ni to occupy interstitial and substitutional sites in the pre-silicide layer. Rapid thermal annealing and Pt alloying determines the stoichiometry and thickness of the layer, while the point defect configurations give rise to lowering of the associated Schottky barrier heights. The pre-silicide layer effectively limits diffusion of Ni into the substrate and therefore allows for the low-temperature growth of Ni2Si and NiSi. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Spray-pyrolysis of a ferrocene–xylene–triethylborane mixture at 900 °C results in a novel “sea-cucumber”-like structure containing carbon and boron. SEM studies show that these structures are hollow with diameter between 100 and 500 nm and lengths varying from 30 to 40 μm. HRTEM and EELS studies reveal that the hollow structures are partly filled with iron. They are formed by a more graphitic internal core, which hardly contains any B. This core is coated by a more disordered B-containing C material. The amount of B in this coating is around 3 at.%. In addition, at this pyrolysis temperature, the growth of open-ended tubular nanostructures (30–40 nm diameter; 100–200 nm length) on the surface of the sea-cucumber-like structure is observed. These tubular nanostructures are not very graphitic and exhibit a similar composition to the coating of the sea-cucumber-like structure (around 3 at.% of B). The study of material produced at different pyrolysis temperatures show that the growth of these tubular nanostructures and the boron content are temperature dependent. Finally, preliminary results corresponding to oxidation resistance studies are presented.

Functional properties of oxide ceramics are often controlled by the addition of dopant elements and the resulting alteration of oxygen vacancy concentrations within grain boundary core structures. A challenge in designing nanoscale ceramic microstructures is forming stable grain boundary networks, while minimizing unwanted impurity concentrations. In this study, it was discovered that the application of electrostatic fields during diffusion bonding of undoped SrTiO3 bicrystals leads to modifications of grain boundary core structures while misorientation angles remained unchanged. The applied electric field not only changes atomic and electronic interface structures, but also causes modifications of ensuing dielectric properties by altering local oxygen vacancy concentrations. The observations for this model system demonstrate the potential to control and modify the microscopic degrees of freedom of grain boundaries in the absence of dopant elements. Field-assisted modifications of grain boundary networks may become a disruptive technology in designing oxide microstructures for a wide range of applications.Functional properties of oxide ceramics are often controlled by the addition of dopant elements and the resulting alteration of oxygen vacancy concentrations within grain boundary core structures. A challenge in designing nanoscale ceramic microstructures is forming stable grain boundary networks, while minimizing unwanted impurity concentrations. In this study, it was discovered that the application of electrostatic fields during diffusion bonding of undoped SrTiO3 bicrystals leads to modifications of grain boundary core structures while misorientation angles remained unchanged. The applied electric field not only changes atomic and electronic interface structures, but also causes modifications of ensuing dielectric properties by altering local oxygen vacancy concentrations. The observations for this model system demonstrate the potential to control and modify the microscopic degrees of freedom of grain boundaries in the absence of dopant elements. Field-assisted modifications of grain boundary networks ...

Silicon has been the semiconductor of choice for microelectronics largely because of the unique properties of its native oxide (SiO2) and the Si/SiO2 interface. For high-temperature and/or high-power applications, however, one needs a semiconductor with a wider energy gap and higher thermal conductivity. Silicon carbide has the right properties and the same native oxide as Si. However, in the late 1990’s it was found that the SiC/SiO2 interface had high interface trap densities, resulting in poor electron mobilities. Annealing in hydrogen, which is key to the quality of Si/SiO2 interfaces, proved ineffective. This paper presents a synthesis of theoretical and experimental work by the authors in the last six years and parallel work in the literature. High-quality SiC/SiO2 interfaces were achieved by annealing in NO gas and monatomic H. The key elements that lead to highquality Si/SiO2 interfaces and low-quality SiC/SiO2 interfaces are identified and the role of N and H treatments is described. More specifically, optimal Si and SiC surfaces for oxidation are identified and the atomic-scale processes of oxidation and resulting interface defects are described. In the case of SiC, we conclude that excess carbon at the SiC/SiO2 interface leads to a bonded Si-C-O interlayer with a mix of fourfold- and threefold-coordinated C and Si atoms. The threefold coordinated atoms are responsible for the high interface trap density and can be eliminated either by H-passivation or replacement by N. Residual Si-Si bonds, which are partially passivated by H and N remain the main limitation. Perspectives for the future for both Si- and SiC-based MOSFETs are discussed.

▪ Abstract In the nanoscience era, the properties of many exciting new materials and devices will depend on the details of their composition down to the level of single atoms. Thus the characterization of the structure and electronic properties of matter at the atomic scale is becoming ever more vital for economic and technological as well as for scientific reasons. The combination of atomic-resolution Z-contrast scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) represents a powerful method to link the atomic and electronic structure to macroscopic properties, allowing materials, nanoscale systems, and interfaces to be probed in unprecedented detail. Z-contrast STEM uses electrons that have been scattered to large angles for imaging. The relative intensity of each atomic column is roughly proportional to Z2, where Z is the atomic number. Recent developments in correcting the aberrations of the lenses in the electron microscope have pushed the achievable spatial resolution and the sensitivity for imaging and spectroscopy in the STEM into the sub-Ångstrom (sub-Å) regime, providing a new level of insight into the structure/property relations of complex materials. Images acquired with an aberration-corrected instrument show greatly improved contrast. The signal-to-noise ratio is sufficiently high to allow sensitivity even to single atoms in both imaging and spectroscopy. This is a key achievement because the detection and measurement of the response of individual atoms has become a challenging issue to provide new insight into many fields, such as catalysis, ceramic materials, complex oxide interfaces, or grain boundaries. In this article, the state-of-the-art for the characterization of all of these different types of materials by means of aberration-corrected STEM and EELS are reviewed.

We show that individual Hf atoms may get incorporated into the SiO2 interlayer which is formed between the HfO2 dielectric film and the Si substrate during rapid thermal annealing. We report atomically-resolved Z-contrast images of a Si/SiO2/HfO2 structure together with first-principles calculations which demonstrate that single Hf atoms are in fact present in the interlayer. The location of individual Hf atoms within the interlayer oxide is closely related to the structure of the amorphous oxide near the Si/SiO2 interface. The Hf defects may affect channel mobility and leakage currents in the HfO2/Si electronic devices.

Valence electron-energy loss spectroscopy (VEELS) in a dedicated scanning transmission electron microscope, vacuum ultraviolet spectroscopy and spectroscopic ellipsometry, and ab initio band structure calculations in the local density approximation have been used to determine the optical properties and the electronic structure of SrTiO3. Assignments of the interband transitions in the electronic structure of bulk SrTiO3 have been determined quantitatively by comparison of VEELS spectra with vacuum ultraviolet spectra and with the ab initio calculated densities of states. The experimentally determined indirect band gap energy is 3.25 eV, while the direct band gap energy is 3.75 eV. The conduction bands in SrTiO3 correspond to the bands composed of mainly Ti 3d t2g and eg states, followed at higher energies by the bands of Sr 4d t2g and eg states, and free electron like states dominating at energies above 15 eV. The upper valence band (UVB) contains 18 electrons in dominantly O 2p states, hybridized with Ti and Sr states, and has a bandwidth of 5 eV. The interband transitions from the UVB to the Ti 3d bands and to the Sr 4d bands give rise to the transitions spanning from the indirect band gap energy of 3.25 eV up to 15 eV. The lower valence band contains 12 electrons in Sr 4p and O 2s states which are separated by 2 eV, while having a bandwidth of 5 eV. The interband transitions from the Sr 4p to the Ti 3d and Sr 4d bands give rise to transition energies spanning from 15 to 24 eV. Interband transitions from the O 2s band to the conduction bands appear at 26 eV. A very narrow band at −33 eV below the top of the valence band is composed of Sr 4s and Ti 3p states and contains eight electrons.

Valence electron energy loss spectroscopy in a dedicated scanning transmission electron microscope has been used to obtain the interband transition strength of a S13 tilt grain boundary in SrTiO3. In a first step the electronic structure of bulk SrTiO3 has been analysed quantitatively by comparing VEELS spectra with vacuum ultraviolet spectra and with ab initio density of states calculations. The electronic structure of a near S13 grain boundary and the corresponding dispersion forces were then determined by spatially resolved VEELS. Also the effects of delocalization of the inelastic scattering processes were estimated and compared with results from the literature. # 2001 Elsevier Science B.V. All rights reserved.

The energy loss near-edge structures in electron energy-loss spectra contain information about bonding characteristics, the electronic structure and coordinations of the excited atoms. We have calculated sets of reference spectra for the normal and for the inverse Mg–Al-spinel using a full multiple scattering approach. By a quantitative comparison of these reference spectra with experimental data ELNES-quantification becomes possible. We characterized the degree of inversion λ by the analysis of the relative peak-intensities and the relative peak-positions within 35 eV beyond the edge onset. The results demonstrate that by using the provided methods ELNES-quantification will become possible when uncertainties in the experiment are reduced and a better fit of the simulations to the experiment is achieved.

This paper reports an investigation of microcrystalline diamond (MCD) films deposited under different conditions to increase thermal conductivity and therefore mechanical quality factor (Q) in micromechanical resonators. Through a study of different deposition conditions, we demonstrate a three-fold increase in thermal conductivity and quality factor. Quality factor measurements were conducted on double ended tuning fork resonators, showing Q = 241,047 at fn = 246.86 kHz after annealing, the highest Q reported for polycrystalline diamond resonators. We further present a study of the unique microstructure of hot filament chemical vapor deposition (HFCVD) diamond films and relate growth conditions to observed microstructural defects.

We use first-principles calculations and experimental data to demonstrate that impurity segregation at heterointerfaces is governed by several factors. In particular, Hf impurities avoid the ${\text{Si-SiO}}_{2}$ interface when present in the ${\text{SiO}}_{2}$ side, might segregate if present in the Si side, but do not cross into ${\text{SiO}}_{2}$. Substitutional Hf impurities in ${\text{SiO}}_{2}$, as revealed by a through-focal series of $Z$-contrast images, act as markers for Si sites, suggesting ordering in the first two Si planes of the amorphous ${\text{SiO}}_{2}$. Finally, we show that dopants in Si segregate at the interface by adopting several distinct configurations and also do not cross into ${\text{SiO}}_{2}$.

Superlattices of suitable perovskite oxides can be used to create novel materials for device applications. Calculations have shown that superlattices with atomically flat, compositionally abrupt interfaces will result in enhanced ferroelectric properties due to strain, changes in bonding and charge compensation at the interfaces. But can these abrupt interfaces be actually grown and monitored at an atomic level? We have shown that it is possible to produce structures hundreds of layers thick using two and three perovskite building blocks.[1?2] Our CaTiO3/SrTiO3/BaTiO3 superlattices exhibited a 50% enhancement in ferroelectric polarization compared with BaTiO3. These films were grown using pulsed laser deposition (PLD) using stoichiometric perovskite targets. The deposition of each unit cell of the films was monitored using the intensity oscillations of the reflection high-energy electron diffraction specular spot.

Information is a high-frequency and low-content phrase that permeates our ordinary language without attracting much attention, since its meaning has long eroded. Even so, is there more to the notion, and in particular, is there philosophy to it? The editors of the series of ‘Handbook of the Philosophy of Science” thought so, when they invited us to contribute a volume, more years ago than we care to remember. But right at the start, a distinction must be made concerning the aim of this text, which comes from the philosophy of language. A Handbook for an established field has a descriptive function in terms of ‘what there is’, serving as a record of insights and issues. But other, activist Handbooks have a performative use, trying to create a new field by a ‘let it be’. The present volume is definitely of the second category. Clearly, one cannot just create an academic discipline by fiat when there is no material to go on. But as it happens, information is a unifying notion across the sciences and humanities, with a backbone of serious mathematical theory. Moreover, there is even a whole discipline of ‘informatics’ (‘computer science’, in the unfortunate terminology used in some countries) which studies the structure of representation and transformation of information by machines, but gradually also by humans, and various hybrids of the two. Indeed, universities in several countries have created schools of Informatics or Information Sciences, highlighting the central role of information and its associated themes of computation and cognition in the modern academic landscape. But this observation again calls for a distinction, this time concerning our purpose. ‘Philosophy of information’ might mean philosophy of the information sciences, just as there is philosophy of the natural sciences, the life sciences, or humanities. Such methodological reflection on specific fields is absolutely necessary given the explosion of relevant technical research. It will be found in abundance in the pages of this Handbook, with authors engaging in foundational analysis of disciplines such as computer science, economics, linguistics, or physics. But there is also the parallel, and in some ways more ambitious aim of information as a major category of thought within philosophy itself, which might have the potential of transforming that whole field. Indeed, major philosophers like Fred

This chapter presents first a chronological account of the incorporation of Nion aberration correctors into the VG Microscopes HB501UX and HB603U (Vacuum Generators, Ltd., Hastings, Sussex, UK) scanning transmission electron microscopes (STEMS) at Oak Ridge National Laboratory (ORNL), the improvement in resolution, and the realization of the additional benefits of the sharper probe. This chapter discusses the improved capability for imaging individual heavy atoms on surfaces or inside a bulk material, which enables spectroscopic identification of a single atom. Subsequently, this chapter also presents a number of case studies in various areas of materials research in which these instrumental advances have provided new insights or provided a new explanation for an old issue. In many cases, microscopy data are coupled with density functional theory, allowing structures suggested from the microscope to be verified and refined. Theory can quantitatively investigate potential impurity sites and determine segregation energies and activation barriers.

The Scanning Transmission Electron Microscope1(STEM) is one of the most useful tools in many areas of atomic-scale materials science and nanocharacterisation. A STEM has the ability to generate local maps of the chemical composition and electronic structure at atomic resolution, even in complex or u...

Core-loss electron energy loss spectroscopy is a powerful experimental tool with the potential to provide atomic-resolution information about electronic structure at defects and interfaces in materials and nanostructures. Interpretation, however, is nonintuitive. Comparison of experimental and simulated compositional maps in $\mathrm{La}\mathrm{Mn}{\mathrm{O}}_{3}$ shows good agreement, apart from an overall scaling of image contrast, and shows that the shape and width of spectroscopic images do not show a simple variation with binding energy, as commonly assumed, or with the size of the orbital excited. For the low lying La ${N}_{4,5}$ edge with threshold at around $99\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, delocalization does not preclude atomic resolution, but reduces the image contrast. The image width remains comparable to that of the much higher lying O $K$ edge with threshold at around $532\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. Both edges show a volcanolike feature, a dip at the column position not previously seen experimentally. In the case of the O $K$ edge, this represents an experimental verification of nonlocal inelastic scattering effects in electron energy loss spectroscopy imaging. In the case of the ${N}_{4,5}$ edge, the volcanolike feature is due to dynamical channeling and absorption of the probe through the specimen thickness. Simulation is therefore critical to the interpretation of atomic-resolution elemental maps.

The aberration-corrected scanning transmission electron microscope provides a new level of sensitivity for analyzing semiconductor device structures. Its sub-Angstrom probe provides not only improved resolution [1], but equally important, greatly increased sensitivity to individual atoms [2,3]. Single Hf atoms are visible within the nanometer thick SiO2 interlayer between a HfO2 high-K dielectric and the Si substrate [4]. Furthermore, the depth of field of the aberration-corrected STEM is just a few nanometers, and Hf atoms can be located in depth to better than 1 nm precision from a through focal series of images (see Fig. 1). Just as with confocal optical microscopy, the series of images can be used to reconstruct the 3D distribution of atoms as shown in Fig. 2. In addition the interface roughness is visible.

Dopant segregation in a ${\mathrm{Mn}}_{\mathrm{x}}{\mathrm{Ge}}_{1\ensuremath{-}x}$ dilute magnetic semiconductor leads to a remarkable self-assembly of Mn-rich nanocolumns, embedded in a fully compensated Ge matrix. Samples grown at $80\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ display a giant positive magnetoresistance that correlates directly with the distribution of magnetic impurities. Annealing at $200\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ increases Mn substitution in the host matrix above the threshold for the insulator-metal transition, while maintaining the columnar morphology, and results in global ferromagnetism with conventional negative magnetoresistance. The qualitative features of magnetism and transport in this nanophase material are thus extremely sensitive to the precise location and distribution of the magnetic dopants.

Recent and ongoing improvements in aberration correction have opened up the possibility of depth sectioning samples using the scanning transmission electron microscope in a fashion similar to the confocal scanning optical microscope. We explore questions of principle relating to image interpretability in the depth sectioning of samples using electron energy loss spectroscopy. We show that provided electron microscope probes are sufficiently fine and detector collection semi-angles are sufficiently large we can expect to locate dopant atoms inside a crystal. Furthermore, unlike high angle annular dark field imaging, electron energy loss spectroscopy can resolve dopants of smaller atomic mass than the supporting crystalline matrix.

The electronic structure of the PdSrTiO{sub 3} interface, which serves as a model system for more complex metal/ceramic interfaces, is studied in terms of local site- and momentum-projected densities of states. Band structures were calculated using density functional theory in the local density approximation. By comparing the local densities of unoccupied states to experimentally determined electron energy-loss near-edge structures, a TiO{sub 2} termination of the SrTiO{sub 3} substrate in contact to the Pd is verified. Furthermore, the local bonding characteristics across the PdSrTiO{sub 3} interface are analyzed by local densities of occupied states overlapping in energy, i.e., by covalent bonding interactions. It is found that the bonding between the Pd and the substrate are dominated by {sigma}-type bonds across the interface.

The 300 kV VG Microscopes’ HB603U STEM at Oak Ridge National Laboratory with a Nion aberration corrector has achieved the first direct image of a crystal at sub-Angstrom resolution, using the incoherent Z-contrast or high-angle annular dark field (HAADF) mode, as shown in Fig. 1a,b. [1] To validate use of the Fourier transform to measure a resolution limit of 0.61A, Fig. 1c compares Fourier transforms of a simulated image and the probe used for the simulation. Excellent agreement is seen for a thin crystal where ideal incoherent imaging applies. Thicker crystals show reduced high frequency transfer, but no spurious sum or difference frequencies [2]. The sub-Angstrom probe allows Z-contrast imaging of oxygen columns next to heavy columns (Fig. 1d). Furthermore, an efficient, simultaneous, aberration corrected, phase contrast image is available using a small axial detector giving improved oxygen visibility, although spurious features are seen between the Sr columns (Fig. 1e). The STEM has become a viable means of acquiring aberration-corrected phase contrast images, with the advantage of simultaneous Z-contrast imaging and EELS.

Electron microscopy has been one of the foremost tools for analysis of semiconducting materials and, in turn, benefits from the processing power provided by faster computers. As semiconductor devices become ever smaller and faster, the shrinking of components means that even single dopant or impurity atoms can significantly affect device performance. Thus the enhanced resolution, sensitivity and new techniques enabled by aberration correction should ensure that this relationship continues.

Aberration correction in scanning transmission electron microscopy represents a major breakthrough in transmission electron microscopy, enabling the formation of sub‐Angstrom probe sizes. Thus, electron microscopy achieved single atom sensitivity. Here, we show how this technique with its unique spatial resolution in combination with high‐resolution electron energy‐loss spectroscopy can be used to investigate atomic and electronic structures of semiconductor interfaces with single atom sensitivity. We employ a Si/HfO2/SiO2/Si high‐k dielectric interface to show the presence of single Hf atoms in the SiO2 interlayer. Furthermore, we demonstrate how local dielectric properties and local band structure information can be obtained by electron energy‐loss spectroscopy.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Quantitative analysis of spatially resolved valence electron energy-loss spectra shows strong physical property contrasts for Sigma5 and near Sigma13 grain boundaries in Fe-doped SrTiO3, resulting in London dispersion interaction energies of 14 to 50 mJ/m(2) between the adjacent grains. The determination of local physical properties of grain boundary cores and the appreciable contribution of long-range London dispersion to interface energies provides new information on formation and control of interfaces in materials.

Near-edge structures of absorption edges in electron energy-loss spectra (ELNES) of SrTiO 3 were calculated and compared to experimental inelastic electron scattering data. The goal of this study was to investigate final-state effects on the electronic structure. Two theoretical approaches were applied: density-functional theory with a band-structure supercell method and a real-space multiple-scattering cluster approach. Within both techniques, the Z +1 approximation was used to model the core hole generated by the inelastic scattering process. For the band-structure calculations, supercells of ( SrTiO 3 ) n (n=1,4,8,16) composition with three-dimensional periodic boundary conditions were applied. The influence of supercell size and shape on calculated site- and symmetry-projected local densities of unoccupied states is assessed quantitatively. Relevant convergence criteria are the length scale set by the spatial extension of the valence-electron screening cloud around the core hole, and the interaction energy of neighbouring core hole centres. For a sufficiently large supercell size, the Z +1 approximation yields a reasonable description of the local densities of unoccupied states probed by the energy losses of inelastically scattered electrons of the Ti L 3 -, O K- and Sr L 3 -absorption edges. The quantitative equivalence of ELNES information extracted from the multiple-scattering cluster calculations and the band-structure supercell calculations is demonstrated. Discrepancies between theoretical and experimental results are discussed.

Summary First results obtained with a Gatan UHV Enfina system, which was attached to a VG HB 501 UX dedicated STEM, are reported. The Enfina system is based on a CCD detector and offers, compared to the previously used photodiode array, a narrower point-spread function, higher sensitivity, and faster read-out capabilities. These improvements are demonstrated with electron energy-loss measurements on various oxides, such as Al 2 O 3 , TiO 2 and SrTiO 3 . It is shown that a better energy resolution is achieved and that acquisition of high-energy absorption edges with a reasonable signal-to-noise ratio becomes possible. Furthermore, we report on the influence of the TEM specimen quality on the energy-loss spectra. Thin amorphous layers at the specimen surfaces, which are induced by ion-milling processes, can modify specific electron energy-loss near-edge structure features. We found that for the investigated ceramics the use of low-energy ion-milling systems is highly recommended, since the loss of energy-loss near-edge structure details by the presence of the amorphous layers is considerably reduced. This is especially true for very thin specimens.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.