bluuebunny/crossref_metadata_2025_split huggingface dataset:
Status of the
SALVE
‐microscope:
Cc
‐correction for atomic‐resolution
TEM
imaging at
20kV
Authors: Linck Martin , Hartel Peter , Uhlemann Stephan , Kahl Frank , Müller Heiko , Zach Joachim , Biskupek Johannes , Niestadt Marcel , Kaiser Ute , Haider Max 
Published: December 2016

With the goal to enable atomic resolution TEM observations on beam sensitive materials the SALVE project had been initiated to develop a dedicated low‐voltage TEM that is corrected for both, spherical and chromatic aberration [1,2].
The centerpiece of the SALVE III microscope is a new quadrupole‐octupole Cc‐Cs‐corrector by CEOS that is based on the so‐called Rose‐Kuhn‐Design [3,4]. The corrector is incorporated into a cubed FEI Titan Themis TEM and has been aligned for five accelerating voltages in the range from 20 to 80kV.
During design of the corrector special care had to be taken to prevent the resolution‐limiting effect of thermal magnetic field noise (Johnson‐Nyquist noise) that causes an image spread and limits the information transfer in Cc‐corrected electron microscopes [5]. As seen in Figure 1(a), these measures have been very successful in that for all desired high‐tensions the finally achieved resolutions exceed the 50mrad milestone. Figure 1(b) exemplarily demonstrates the achieved information limit on a purely amorphous 2nm tungsten sample at an accelerating voltage of 20kV. For the two shown perpendicular directions the Young's fringes significantly surpass the 50mrad aperture. In order to “use” the transferred information in a proper way, the phase plate, i.e. the aberration function, has to be well‐controlled beyond the 50mrad‐angle. This requires accurate control over axial aberrations up to including 5th order, and ‐for a considerable field of view‐ access to off‐axial aberrations. The aberration measurement in Figure 1(c) demonstrates that all unround axial aberrations as well as the off‐axial aberrations can be tuned sufficiently small. At the same time, the round aberrations can be adjusted for a suitable phase contrast transfer function (indicated in green color). Consequently, as shown in Figure 1(d) even at 20kV atomic resolution imaging becomes reality.
The chromatic aberration causes inelastically scattered electrons, i.e. electrons of lower energy, to be focused much stronger. This effect is compensated in the Cc‐corrected instrument. Figure 1(e) compares the energy‐dependent defocus effect of a Cc‐uncorrected TEM (red line, Cc=1.45mm) and the SALVE microscope (measurements: black dots; 3rd order fit: dashed line) at 20kV. While the gradient of the Cc‐uncorrected case is too steep to be distinguished from the axis of the ordinate in the magnified area, the SALVE instrument is capable to image a 20eV window with defocus changes of only 2nm. This will enable new imaging modes such as high‐resolution EFTEM at very low voltages. [6]
Transmission electron microscopy investigation of
Mg‐Zn
alloy processed by severe plastic deformation
Authors: Němec Martin , Gärtnerová Viera 
Published: December 2016

Magnesium alloys possess great potential owing to advantageous properties in various fields such as structural applications, electronic devices or hydrogen and thermal energy storage. Use of Mg alloys for biomedical implants also attracted enormous attention recently. Properties of Mg and its alloys can be significantly improved via design of alloys with precipitation hardening effect and grain refinement using severe plastic deformation (SPD) techniques. Mg‐Zn based alloys are among the most important Mg alloys and have been investigated for more than a hundred years. With a most recent development of various SPD techniques, there is a number of processing routes which may significantly improve the alloys properties. However, fundamental knowledge about an impact of SPD on microstructure of these alloys at nanoscale is insufficient or missing in many cases.
In this work, deformation behaviour of an α‐Mg matrix and Mg‐Zn intermetallic particles in the Mg‐12wt.% Zn alloy subjected to equal‐channel angular pressing with applied back pressure (ECAP‐BP) is characterized using transmission electron microscopy (TEM) techniques at nanoscale. Magnesium with 99.9% purity and an appropriate amount of high‐grade Zinc were melted in a graphite crucible under an Ar atmosphere. The subsequent thermal treatment consisted of annealing at 320°C for 20 hours and quenching into warm water. The material was then processed by ECAP (4 passes via Bc route) with applied BP of ~400 MPa to prevent cracking during processing. The processing temperature was gradually decreasing from 200 °C to 185 °C, 170 °C and 155 °C for 1st, 2nd, 3rd and 4th ECAP‐BP pass, respectively, to obtain ultra‐fine grained structure.
Following TEM techniques are employed for micro‐ and nano‐ structural analysis: Bright‐field (BF) imaging; selected area electron diffraction (SAED); high‐resolution transmission electron microscopy (HRTEM); high‐angle annular dark field ‐ scanning transmission electron microscopy (HAADF‐STEM) imaging; and electron energy‐loss spectroscopy (EELS). All techniques were performed using an FEI Tecnai TF20 X‐twin, which operated at 200 kV.
The atomic lensing model: extending
HAADF STEM
atom counting from homogeneous to heterogeneous nanostructures
Authors: van den Bos Karel H W , De Backer Annick , Martinez Gerardo T , Winckelmans Naomi , Bals Sara , Nellist Peter D , Van Aert Sandra 
Published: December 2016

Counting the number of atoms in each atomic column from different viewing directions has proven to be a powerful technique to retrieve the 3D structure of homogeneous nanostructures [1]. In order to extend the atom counting technique to heterogeneous materials, this work presents a new atomic lensing model facilitating both atom counting and 3D compositional determination in such materials.
In the quantitative evaluation of high angle annular dark field scanning transmission electron microscopy (HAADF STEM) images the so‐called scattering cross‐section (SCS) has proven to be a successful performance measure [1–3]. Its monotonic increase with thickness can be used to count the number of atoms in homogeneous materials with single atom sensitivity [4]. However, for heterogeneous materials, small changes in atom ordering in the column can change the SCS (Fig. 1), significantly complicating atom counting. This depth dependency requires a quantitative method to predict SCSs of all possible 3D column configurations, already more than 2 million for a 20 atoms thick binary alloy. Image simulations can provide this information, but the amount of required simulations makes it an impossible task in terms of computing time. Therefore, a new atomic lensing model is developed based on the principles of the channelling theory [5], where each atom is considered to be an electrostatic lens resulting in an extra focussing effect on the probe. This model allows one to predict the SCSs of mixed columns based on the lensing factors of the individual atoms in monotonic atomic columns. As compared to a linear model neglecting channelling, this new approach leads to a significant improvement in the prediction of SCSs which is not restricted to the number of atom types (Fig. 2) and can be used for a wide range of detector angles (Fig. 3).
The power of the atomic lensing model to accurately predict SCSs enables one to extend the atom counting technique to heterogeneous materials. Here, simulated SCSs can be matched to the measured experimental SCSs. Next, the 3D structure can be determined by combining atom counts from different viewing directions. In this presentation, this technique will be demonstrated on experimentally recorded images of an Au@Ag nanocrystal. Another advantage of the atomic lensing model is its ability to accurately predict the atom ordering in the column from experimental SCSs (Fig. 1). Therefore, it opens up the possibility to extract 3D information from a single image. This ability will be presented on a simulated image of an Au@Ag nanorod.
In conclusion, a new atomic lensing model is developed which is of great importance for extending the atom counting technique from homogeneous to heterogeneous nanostructures.
Time‐resolved imaging and analysis of single atom diffusion on graphene oxide
Authors: Furnival Tom , Leary Rowan , Tyo Eric C , Vajda Stefan , Thomas John Meurig , Bristowe Paul D , Midgley Paul A 
Published: December 2016

Single atoms and small atomic clusters offer a range of novel, tunable properties for a number of applications such as selective catalysis [1]. Achieving precise control of the desired properties of these systems first requires an understanding of the interaction between the cluster and its support. Advances in aberration‐corrected scanning transmission electron microscopy (STEM) mean that atomic resolution imaging and characterisation is now achievable for many materials. Observing individual atoms and small clusters remains difficult, however, due to low signal‐to‐noise ratio and beam‐induced motions causing blurring during image acquisition. One route around these problems is to acquire rapid image sequences in an effort to reduce the electron dose and also to capture any dynamic behaviour of the atoms. Making use of the spatial and temporal correlations between frames, and using a novel processing method based on singular value thresholding [2], we have developed robust approaches to recover individual atomic positions, including STEM acquisition rates of 10 frames per second or better [3].We have applied the approach to the study of catalytically‐important copper atoms on few‐layer graphene oxide (GO), where the presence of functional groups on GO may aid the control of deposited clusters by acting as preferential pinning sites. Processing and analysis of an annular dark‐field STEM image sequence reveals a range of behaviours, with some strongly‐pinned atoms and other more mobile atoms undertaking random walks on the surface (Figure 1b). Further investigation of the jump distances (Figure 1c) and mean‐squared displacements (Figure 1d) reveals that the diffusion of adatoms on GO is anomalous. We combine this information with ab‐initio DFT calculations to provide new insight into the formation and behaviour of small atom clusters under an electron beam, and the interactions between few‐atom catalysts and high surface area supports.
Dynamic oxidation and reduction of catalytic nickel nanoparticles using
E(S)TEM
Authors: Lloyd David , LaGrow Alec , Boyes Edward , Gai Pratibha 
Published: December 2016

For many materials, nanoparticles show enhanced catalytic activity and selectivity compared to their bulk state [1]. While catalytic nanoparticles have many industrial, economic and environmental benefits, they also present new challenges, the most significant of which is to characterise the intermediate phases and structural changes to the active catalyst species under reaction conditions. TEM is uniquely suited to the study of solid‐state heterogeneous catalysis as it allows us to directly characterise the catalyst with regard to its nanostructure on the atomic scale. Complementary spectroscopy techniques such as EDS and EELS can be used in tandem with imaging to add chemical data to the structural observations. The in‐situ capabilities of the E(S)TEM allow for intermediate catalyst phases and transformations to be observed, some of which are only present under reaction conditions and would be lost using ex‐situ methodologies [2].
Here we present a study of the dynamic nature of Ni based catalysts under redox conditions relevant to industrial processes [3, 4]. The increased activity of finely divided Ni means that it is important to directly observe the Ni nanoparticles rather than interpreting models based on bulk or ex‐situ techniques. Many chemical processes that rely on Ni catalysts involve exposure to both oxidising and reducing gas in the reaction environment. Under reducing and oxidising conditions the structure of Ni nanoparticles is dynamic and involves transitions between single crystal Ni, core‐shell Ni/NiO and hollowed Kirkendall‐like structures [5, 6]. These changes are dependent on the material properties (size, shape and support interaction) and reaction parameters (temperature, gas type and pressure). Furthermore, these dynamic structure/shape changes influence the stability of the catalyst, which in turn is controlled by the reaction environment. As such, this area of research is crucial for understanding the conditions necessary for attaining and maintaining a particular catalytic species and designing the reaction routes required to reactivate spent Ni catalysts.
Environmental TEM/STEM has been used to probe the dynamic oxidation of Ni nanoparticles. The particle size, reaction time and temperature dependencies of the oxidation process have been investigated using both model and industrial Ni catalysts. Furthermore, we have applied the same in‐situ techniques to reveal the conditions needed for complete reformation/reactivation of the original Ni species.
Microstructure of glass ceramics synthesized from chromium waste
Authors: Varitis Savvas , Kavouras Panagiotis , Kaimakamis George , Pavlidou Eleni , Vourlias George , Karakostas Theodoros , Komninou Philomela 
Published: December 2016

The microstructure of different glass ceramic materials, obtained by thermal processing of vitrified products synthesized from tannery waste, was investigated using electron microscopy (TEM) techniques. Preliminary structural characterization was conducted by X‐Ray Diffraction (XRD) while morphologies and compositions of the materials at the mesoscopic scale were attained using Scanning Electron Microscopy (SEM) and Energy Dispersive X‐ray Spectroscopy (EDXS).
A first series of materials were synthesized by sintering chromium rich ashes of tannery waste with low grade soda lime glass powder. Three different mixtures were prepared with proportions 30/70, 40/60 and 50/50 of Cr‐ash over glass powder and sintered at 600°C, 800°C, 1000°C and 1200°C [1]. Depending on the temperature, crystalline phases with chromium and non‐chromium content were solidified. At the low temperatures the resulting products were opaque ceramics with granular morphology and high porosity, as shown in Fig. 1. At the high temperatures they consisted of a vitreous matrix with dispersed crystalline phases having the morphology of typical glass‐ceramics as those pointed by the white arrow in Fig. 2.

A second series of materials were synthesized using chromium ash (10wt%‐20wt%) and SiO
2
, Na
2
O and CaO as vitrifying agents, in different relative proportions considering the low solubility of chromium inside the silicate melts [2]. Only the product with the lowest Cr‐ash proportion was X‐Ray amorphous with no indication of crystallites. HRTEM observations verified that the product retained the amorphous character even at the nanoscale since no nanostructured crystallites were detected. In all other vitrified products Eskolaite (Cr
2
O
3
) crystallites of hexagonal shape, shown in Figure 3, were grown in the melt. Devitrification of the as‐casted products resulted to various crystalline phases dispersed within the vitreous matrix, depending on the initial batch composition. Eskolaite crystallites were not affected by the thermal processing and Devitrite (Na
2
Ca
3
Si
6
O
16
), Combeite (Na
4
Ca
4
Si
6
O
18
) and Wollastonite (CaSiO
3
) crystallites were grown. Figure 4 illustrates a HRTEM image showing a Wollastonite (CaSiO
3
) crystallite in the devitrified product with 13wt% Cr‐ash, viewed along the [0 1 1] zone axis. This crystallite has the triclinic structure of 1A‐CaSiO
3
.
Optically Coupled Plasmonic Nanopores Observed by Cathodoluminescence Scanning Transmission Electronmicroscopy
Authors: Sannomiya Takumi , Saito Hikaru , Juliane Junesch , Yamamoto Naoki 
Published: December 2016

Control of the optical properties of nano‐plasmonic structures is essential for next‐generation optical circuits and high‐throughput biosensing platforms. Realization of such nano‐optical devices requires optical couplings of various nanostructured elements and field confinement at the nanoscale. In particular, symmetric coupling modes, also referred to as “dark modes”, have recently received considerable attention because these modes can confine light energy to small spaces. Although the coupling behavior of plasmonic nanoparticles has been relatively well‐studied, couplings of inverse structures, i.e., holes and pores, remain partially unexplored. Even for the most fundamental coupling system of two dipolar holes, comparison of the symmetric and anti‐symmetric coupling modes has not been performed. Here, we present a systematic study of the symmetric and anti‐symmetric coupling of nanopore pairs using cathodoluminescence by scanning transmission electron microscopy (CL‐STEM) and electromagnetic simulation.
The nanopore samples were fabricated by colloidal lithography and film transfer by wet etching of the sacrificial layer. To achieve very close separation of nanopore pairs and to obtain high spatial resolution in STEM, we chose ultra‐thin, free‐standing film structures. For the measurement of single and coupled pairs of nanopores, 135 nm nanopores in an AlN(8 nm)/Au(16 nm)/AlN(8 nm) trilayer membrane were used (Figure 1b). With this sandwich layer structure, it is possible to obtain very thin and stable metal layers, even at high temperatures.
For CL‐STEM measurement, 80 kV acceleration was used to avoid possible damage due to relatively high beam current. (5nA) Depending on the electron beam position it is possible to distinguish the symmetric and anti‐symmetric dipolar coupling modes.(Fig. 1) The observed symmetric coupling mode, approximated as a pair of facing dipoles, appeared at a lower energy than that of the anti‐symmetric coupling mode, indicating that the facing dipoles attract each other. The anti‐symmetric coupling mode splits into the inner‐ and outer‐edge localized modes as the coupling distance decreases. These coupling behaviors cannot be fully explained as simple inverses of coupled disks. Electromagnetic simulation by finite difference time domain (FDTD) also showed consistent coupling behaviors. Models of FDTD simulation showed that the inner‐ and outer‐edge anti‐symmetric modes become fully localized with minimal influence of the opposite edges as the coupling distance decreases. Symmetric and anti‐symmetric coupling modes are also observed in a short‐range ordered pore array (Fig. 2), where one pore supports multiple local resonance modes, depending on the distance to the neighboring pores.
Development of New Generation Cryo
TEM
Authors: Hosogi Naoki , Kaneko Takeshi , Ishikawa Isamu , Yuasa Syuuiti , Hiyama Kimitaka , Fujimoto Naoki , Chiyo Izuru , Kamoshita Akihito , Ohkura Yoshihiro 
Published: December 2016

Cryo transmission electron microscopy (TEM) provides structural information of a specimen close to its natural state without any disturbance, due to the specimen preparation process, which exclude chemical reactions and physical stimulations. Recently, cryo TEM produces very exciting results of structural biology in combination with single particle analysis and electron tomography, since application field of the method expand to non crystalline samples or huge molecules.
We developed a new generation cryo TEM, which achieves high throughput and high usability. This microscope equips 200 kV field emission gun (FEG). Users can choose it from a Schottky‐type (TFEG) or a cold FEG (CFEG). Since the energy spread of the emitted electrons from the CFEG is about 50% of TFEG and the size of the virtual source is less than 10 nm, the electron beam has a high coherences. With such beam, cryo TEM image has high contrast due to its high spatial coherence and is less affected by chromatic aberration due to its high temporal coherence. In low dose imaging, where the image resolution is mainly determined with dose density for the image. In the low dose density, S/N of image mostly determined by a statistical noise of electrons, since dose density in cryo TEM is typically several tens of electrons for angstrome square. Namely, the resolution is determined with the competition between the statiscal noise and image contrast. It means CFEG has posibility to have higher resolution for cryo TEM works.
Since this microscope also has dedicated cryo stage, cryo TEM observation can be performed at low temperature < 100 K and with low grow ratio of ice contamination. In addition, this cryo stage is compatible for multi‐specimen auto‐loader, so users can exchange specimens automatically. It also has some automation functions, such as liquid nitrogen auto‐refill system and auto acquisition software (JEOL Automated Data Acquisition System: JADAS). These automation functions will help users to perform high throughput works. On another front, the electron gun chamber and the TEM column are evacuated with sputter ion pump and turbo‐molecular pump, because of this, a sample is kept in oil‐free environment.
In addition, this microscope is compatible with omega‐type energy filter and Zernike or hole‐free phase plate. The cryo specimens exhibit low contrast in TEM images even using large defocus phase contrast imaging. The Cryo TEM is more advantageous when it is combined with these techniques of contrast enhancement.
Charging kinetics features of different modifications of theAl2O3–dielectrics (sapphire, polycrystalline and ceramics) under electron‐beam irradiation
Authors: Rau Eduard , Tatarintsev Andrey , Khaidarov A , Kupreenko Stepan 
Published: December 2016

The phenomenon of charging dielectrics via the electron‐beam irradiation has been studied very intensively. However, published in recent years the results of experimental and theoretical studies of dielectrics charged under electron irradiation gives contradictory description of this phenomenon [1–6]. These contradictions arise mainly due to the differences in the approaches and fragmentation of experimental studies and differences in used physical models of charging mechanisms.In this report on the basis of extensive experimental data of simultaneous measurement of key charging parameters we are given a balanced assessment of the multiple factors influencing on the charging process. We present the new features of this process and given its interpretation.Based on comprehensive methodology [7, 8], we measure simultaneously the main charging parameters of different modification Al2O3, such as surface potentialVS, electron‐emission currentIσ, displacement currentID, and accumulated chargeQversus time of electron irradiation. The experimental setup that allows simultaneously measure the basic charging parameters published in the [9].The experimental results of complex research of the key charging parameters for sapphire and ceramics Al2O3are presented in Fig. 1, Fig. 2, Fig. 3 and Fig 4. The main conclusion of these investigations is that although charging processes of dielectric targets are self‐consistent and mutually dependent, the accumulation of the negative charge and, correspondingly, an increase in the charging potential, is the dominant (leading) effect, while the variation in the secondary electron emission coefficient, which depends on the surface potential, is a driven adjusting process. For this reason, a delay occurs in the time for attaining the equilibrium of two fundamental charging parameters, viz., the emission current (a short‐time process) and charging potential (a long‐time process). In other words, for all modifications Al2O3coefficient of secondary electron emissionσreaches an equilibrium value for used doses of electron irradiation significantly faster than the surface potential.This work was funded thanks to the support of RFBR (grant 15‐02‐01557).