bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separating Magnetic and Non‐magnetic Signals at the
Fe/MgO
Interface
Authors: Spiegelberg Jakob , Thersleff Thomas , Rusz Ján 
Published: December 2016

Despite various efforts, it remains an experimentally challenging task to access magnetic properties at (sub) nanoscale. One route towards a direct measurement of magnetism is the measurement of electron magnetic circular dichroism (EMCD) [1]. Being based on the measurement of electron energy loss (EEL) spectra, EMCD can in principle be measured at atomic resolution and can open the door to study exciting new area of physics such as magnetism in the vicinity of defects or interfaces. However, in addition to general concerns of low signal to noise ratios of EMCD spectra measured at high resolutions calling for a statistical data treatment, there might be other, non‐magnetic contributions to the signal which cause a change in the white line ratio of the L3/L2 edge peak of the magnetic species. These white line changes might be related to the occurrence of a different chemical species of the same element, e.g., due to in situ oxidation of the sample, or also to position dependent changes of the electron wavefunction if the EMCD experiment is carried out at atomic resolution [2]. Such effects may render the correct interpretation of EMCD signals impossible if they can not be clearly separated from the true magnetic signal. The issue calls out for a statistical tool to separate the components.
We demonstrate how a canonical polyadic decomposition (CPD) [3],[4],[5] can be used to separate magnetic and non‐magnetic signals measured at the Fe/MgO interface. The system has recently received a lot of attention as a candidate for magnetic tunnel junctions due to its large tunneling magnetoresistance (e.g. [6],[7]), its magnetic properties, epecially at the interface are thus of interest. Through the additional explanatory power of CPD, insight is gained on a perceived increase of orbital to spin moment ratio at the interface [8]. Besides the spectral components and their spatial maps (Fig.1), CPD also returns a vector containing the weight of the respective component in the data sets measured with an aperture position such that the sign of the EMCD signal is positive, negative and such that the magnetic component vanishes (Fig.2). The components shown below indicate a significant non‐magnetic white line branching towards the Fe/MgO interface.
CPD can not only be used as a technique to extract EMCD from noisy data and separate it from potential non‐magnetic signals, targeting both the aforementioned problems, but it can be generalized to any problem of identifying different signal contributions in experiments where multiple data sets are measured on the same sample area, such as momentum resolved EELS. It possesses desirable features such as uniqueness while not constraining the components along either of the modes and comparatively low computational costs. The assumptions on the tensor's structure match the physical model and thus lead to directly interpretable components. Hence, CPD is a useful addition to the set of statistical tools for the analysis of microscopy data.
Identification of core‐shell structures in high active Pt‐alloy catalysts for oxygen reduction by electron spectroscopy
Authors: Deiana Davide , Velazquez‐Palenzuela Amado Andres , Escudero‐Escribano Maria , Masini Federico , Stephens Ifan , Chorkendorff Ib , Hebert Cécile 
Published: December 2016

A potential clean alternative to traditional power sources, in particular for the automotive industry, is represented by low temperature fuel cells [1].
The major limitation of this promising technology lies in the high loading of the mostly used catalyst Pt necessary to drive the chemical reactions at the electrodes of the cells, impacting significantly on costs.
Generally, the performance is limited by the sluggishness of the Oxygen reduction reaction (ORR) that occurs at the metal catalyst surface present at cathode. Therefore, a great effort is put in finding catalysts with higher efficiency for the ORR [2][3].
A promising strategy for enhancing the ORR activity is to alloy Pt with other metals [2]. However, commercially available Pt alloys with late transition metals are mostly unstable under the harsh conditions in a fuel cell cathode [4].
Pt‐Gd has been identified as a promising material among a new class of Pt‐lanthanide alloys as highly performing catalyst for the ORR in both activity and stability, surpassing the previously reported Pt‐Y [5‐7].

The experimental results have shown that Pt
x
Gd nanoparticles exhibit an outstanding ORR activity of 3.6 A (mg Pt)
‐1
at 0.9 V with respect to a reversible hydrogen electrode [8].

To fully understand the enhanced performance of these catalysts, the knowledge of the detailed structure and elemental distribution at the nanoparticle level is of extreme importance. Here we present an advanced Scanning Transmission Electron Microscopy (STEM) study of Pt
x
Gd nanoparticle catalyst.

High resolution HAADF‐STEM imaging and STEM‐EDX spectrum imaging has been performed in a double C
s
‐corrected FEI Titan Themis 60‐300 at CIME laboratories, equipped with a monochromated high‐brightness FEG, an EDS SUPER X system with a 0.7 srad of solid angle and a Gatan GIF Quantum ERS high energy resolution EELS spectrometer and energy filter.

Pt
x
Gd nanoparticles have been prepared through a gas aggregation technique in a multi‐chamber ultrahigh vacuum system (Omicron Multiscan Lab) at DTU CINF laboratories.

Figure 1 shows a high resolution STEM micrograph and STEM‐EDX elemental maps of Pt
x
Gd nanoparticles after exposure to ORR conditions during electrochemical tests. From the micrographs the sample presents a polycrystalline structure with a Pt rich shell and a Pt‐Gd core. The formation of the Pt shell is assigned to the initial dissolution of Gd when exposed to the acidic solution of the ORR test.
Defocus and probe‐position coupling in electron ptychography
Authors: Cao Shaohong , Li Peng , Maiden Andrew , Rodenburg John 
Published: December 2016

One of the most promising applications of electron ptychography is the possibility of converting a conventional SEM, with a relatively poor stability envelope, into a high‐resolution TEM. This is simply achieved by placing a transmission specimen in stage and a CCD camera placed below the specimen [1]. SEM ptychography does not need any image‐forming lenses: the objective lens is only used to generate a conical illumination. Defocusing this into a large area allows for a large ptychographical step size and a very large field of view. High resolution is obtained by solving the phase problem for the high‐angle scattered intensity (lying outside the Ronchigram) via iterative algorithms such as ePIE [2] and DM [3]. See Fig. 2a, where gold atomic fringes in gold nano particles on a carbon support film are clearly visible in a ptychographic reconstruction obtained from a conventional SEM (an FEI Quanta 600 SFEG at 30keV, data from [1]). We also solve for the illumination function, which in the case of conical illumination has a uniform curvature dependent on defocus.
A complication of electron (as opposed to visible light and X‐ray) ptychography is that is normally necessary to solve also for the illumination positions [4] because of errors in the scan coils resulting from magnification calibration inaccuracy and hysteresis. However curvature in the illumination and probe shift are coupled. Figure 1 shows a simplified ray diagram. For any two specimen planes where the ratio of the shift distance () and the ratio of the feature size in the object () equals the ratio of the defocus (), the resulting Ronchigrams will behave identically as the probe is shifted. In fact in the presence of wave interference the correct solution is unique, but for probe position‐searching algorithms that are necessarily guided by the Fourier error metric, the bright intensity of the Ronchigram dominates. When partial coherence is present (so that Fresnel effects in the Ronchigram are supressed) the problem is exacerbated, generally resulting in a distorted probe position lattice (Fig. 3), a wrong estimate of the defocus, and an inconsistent reconstruction in which lattice fringes are strongly delocalised. Of course, delocalisation renders the reconstruction entirely invalid, like an out‐of‐focus conventional TEM image.
We explore the coupled position‐defocus stagnation problem based on both experimental and simulated data. We report progress on various methods that can resolve this important issue.
Ni
‐based superalloy: crystalline orientation mapping and gamma‐gamma′ phases discrimination with the iCHORD method
Authors: Langlois Cyril , Charpagne Marie‐Agathe , Dubail Sébastien , Douillard Thierry , Bozzolo Nathalie 
Published: December 2016

Electron backscatter diffraction (EBSD) is routinely employed as a characterization tool to obtain individual grain orientations, local texture and phase identification. However, in the case of γ ‐ γ′ Ni‐based superalloys, the EBSD technique allows mapping the orientations but fails discriminating the two phases because their diffraction signature is too similar. A coupling with EDX analysis for instance helps to identify the two phases but suffers from the lack of spatial resolution of the EDX maps. Another way to discriminate the two phases is to use the BSE images, sensible to the chemistry, but because of the difference in the geometry of acquisition of the EBSD images and the BSE images, superposition of the two information is complicated by strong spatial distortions. In this context, any new technique that can lead to an easier phase and orientation mapping would be welcome, especially to resolve the fine secondary γ′ precipitates (typically few tens of nanometers).
We proposed recently the iCHORD method (for ion CHanneling ORientation Determination), aiming at constructing orientation maps based on the well‐known channeling contrast phenomenon observed in a rotation series of ionic images (see figure 1) [1]. The proof‐of‐concept of the iCHORD method was established using a titanium nitride specimen (TiN) and further tests were conducted on different metallic materials. In the case of Ni‐based superalloys, the channeling contrast is very strong and allows obtaining quite easily orientation maps comparable in all aspects to the one obtained by the EBSD technique. Furthermore, when using the ion beam to scan the surface, a secondary ion signal can be detected and used for imaging the sample. In the case of γ ‐ γ′ superalloys, this secondary ion signal provides a strong contrast between the γ phase and the γ′ phase (see figure 2). Because of the identical geometry of acquisition for the iCHORD orientation maps and the secondary ion images, both information can be easily superimposed. It allows discriminating between the two phases and giving their crystallographic orientations (see figure 3). Moreover, the spatial resolution of the secondary ion images is around few tens of nanometers, which is far better than the resolution of ~1 µm of EDX maps.
To conclude, the advantages of using ion images to study Ni‐based γ ‐ γ′ superalloys are discussed, particularly the benefits taken from the higher spatial resolution and the ease of mixing orientation and phase information.
Dynamic‐Transmission Electron Microscopy at the Relativistic Electron Gun for Atomic Exploration (
REGAE
) for live cell imaging
Authors: Manz Stephanie , Keskin Sercan , Besztejan Stephanie , Zeitler Benno , Azim Sana , Kassier Guenther , Buecker Robert , Venegas‐Rojas Deybith , Riekeberg Svenja , Zhang Dongfang , Casandruc Albert , Loch Rolf A. , Zhong Yinpeng , Delsim‐Hashemi Hossein , Epp Sascha W. , Floettmann Klaus , Trieu Hoc Khiem , Rentmeister Andrea , Miller R. J. Dwayne 
Published: December 2016

With the relativistic electron gun for atomic exploration (REGAE) we seek to observe structural dynamics both in real space imaging and diffraction [1]. REGAE is based on a RF gun accelerator and operates in the range from 2 to 5 MeV. RF gun technology allows high brightness for electron pulses at high energy. The machine is equipped with an RF cavity system, allowing for picosecond bunches with energy spread compensation to prevent limitations by chromatic aberrations and space charge. A custom made lens system for 3 MeV pulse energy system is set in place.
The presentation will include a discussion on space charge induced aberrations in dynamic HVEM, give estimates about the anticipated resolution and discuss the prospects for dynamic transmission electron microscopy of organic samples in environmental cells. Recent results making use of nano‐fluidic cell technology developed in house will be presented as an outlook: DNA – nanoparticle multimers have been studied regarding their dynamic in liquid and stability under electron irradiation during TEM imaging in a conventional 200 keV microscope [2]. First experiments towards imaging dynamics in living cancer cells under environmental conditions in the TEM will be discussed [3].
Transport of Intensity Equation (
TIE
) without filtering and
TIE
videos
Authors: Wild Johannes , Vogel Michael , Schwarzhuber Felix , Back Christian , Zweck Josef 
Published: December 2016

In the transmission electron microscope (TEM) almost all specimens are very thin and create mainly phase shifts of the electron beam, hardly any absorption. The phase shift gives a lot of information about the specimen like e.g. thickness modulations, electric fields or magnetic fields. Measuring the phase by conventional imaging techniques is quite difficult as in general only changes in intensity are detected.
One way to get the phase difference between object wave and a reference wave is the transport of intensity equation (TIE) which was initially developed for light microscopes [1]. The most common use of the TIE is to input a linear approximation for the intensity changes which occur when the image is taken at different values of defocus along the z direction and then to solve the equation for the phase. Thus it is possible to calculate the phase in good approximation. From the phase it is e.g. possible to evaluate direction and strength of intrinsic magnetic and electric fields of the specimen.
Recent publications use mainly a commercially available software to perform TIE calculations [2‐4]. This software uses different filter algorithms which are not all known to the user. Therefore it turns out to be difficult to interpret the TIE reconstructions as the the filtering may create measurement artifacts.
Here we present a home written TIE Matlab code to calculate the phase. Our aim was to create a transparent code where the user is aware of all parameters. We use as little filtering as possible to minimize the room for misinterpretations and clearly show where modifications have been made to the original data. We are even able to calculate useful TIE images without any filtering as shown in figure 1.

Our software is capable of calculating magnetic or electric field maps from focal series (in‐focus, over‐focus, under‐focus). Further, it is possible to create automated multiple TIE images for videos to visualize e.g. the temporal development of a magnetic structure. We show one example of a fluctuating skyrmion lattice in Cu
2
OSeO
3
.

We will provide the code as a Matlab applet for everybody interested for free.
STEM
investigation of titania supported gold nanoparticles stabilized by ceria
Authors: Hungría Ana , Tinoco Miguel , Río Eloy Del , Manzorro Ramón , Cauqui Miguel A. , Calvino Jose Juan , Perez‐Omil José A. 
Published: December 2016

Gold nanoparticles show an excellent catalytic performance in energy production related processes such as low temperature CO oxidation, PROX and WGS reactions [1‐2]. The effect of the support, like titania or ceria, and/or the presence of different kinds of promoters on the catalytic performance of gold have also been investigated, and a general agreement about the advantages of using reducible oxides is deduced from a revision of the most recent literature. Gold catalysts have also proven to be active in environmental reactions as those occurring in the catalytic converters (TWC) for depuration of exhaust gases in vehicles. The use of gold as a component of the current TWC formulations, substituting the more critical Pt and Pd, would only be feasible if the excellent catalytic properties of this metal could be maintained after exposure at high temperature operating conditions. However due to its relative low melting point gold suffers a severe sintering process starting at temperatures of around 473 K [3].
In order to investigate the stabilization of gold nanoparticles a reference system, 1.5 wt% Au/TiO2World Gold Council catalyst, was modified by depositing on its surface a monolayer of CeO2by incipient wetness impregnation to a final ceria molar loading of 5.4%.Scanning Transmission Electron Microscopy (STEM) studies show that the dispersion of the gold nanoparticles remained unchanged after the impregnation in a value about 36%. Afterwards, both catalysts were tested in consecutive CO oxidation reaction loops at increasing final temperatures. In these cycles, the ceria‐modified catalyst showed not only a higher activity but, more importantly, a largely enhanced stability against deactivation.
Scanning Transmission Electron Microscopy has provided key information to rationalize the origin of the stabilization effect provided by ceria. In particular, STEM‐HAADF images haveclearly revealed the presence of nanometer‐sized ceria rafts, less than 1 nm thick, on the surface of the fresh CeO2(5.4%)/Au(1.5%)/TiO2catalysts. After the CO oxidation test at the highest temperature, 1223 K, the conventional WGC catalyst suffered from a very severe Au nanoparticle sintering, Figure 1(a),whereas Au nanoparticle growth was very much limited in the ceria‐modified catalyst after the same aging test, Fire 1(b).
Cs‐corrected STEM results reveal that a major fraction of the Au nanoparticles (75%), comprising all the smaller ones (< 5 nm), was contacting the ceria nanolayers. This evidences an important stabilizing effect of the proposed surface modification. Moreover, these results open up possibilities for gold catalysts in applications where high temperatures are reached under working conditions.
Microstructural and chemical characterization of the system
CaO‐Al2O3
using environmental scanning electron microscopy (
ESEM
)
Authors: Berent Katarzyna 
Published: December 2016

The calcium and alumina oxide is a highly interesting functional materials. In the binary compound 12CaO·7Al
2
O
3
has a unique crystal structure as a nano‐sized cage with free oxygen anions randomly distributed inside the cages. C12A7 has gained much attention for potential applications in various fields, such as ion conducting solid electrolyte, field and ion emitters, oxidizing catalyst and as a transparent conductive oxide (TCO) in flat panel displays, solar cells and energy conservation (smart windows) devices [1, 2]. The functional properties of electrides are strongly depend on the microstructure. There is in the literature some information about the influence of specific surface area and impurities of alumina on the sintering behaviour of an alumina material. But in this study, the objective is to determine if the various processing techniques have an influence on the microstructure evolution of materials made from alumina and calcium oxide.

Post‐fabrication C12A7 samples were subjected to heat treatment using different processing methods in order to achieve desired crystal structure. The final products were prepared by sintering (1) and melted in an electric furnace (2). Crystalline and amorphous phases were obtained.
The aim of the present study was to evaluate the microstructure of CA ceramics under different melting conditions. The microstructure characteristics were analyzed by means of optical microscopy (OM), X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDXS) and environmental scanning electron microscopy (ESEM).
For scanning electron microscopy (SEM) examination, sintered specimens were cut and polished. ESEM allows the direct examination of specimens without a conductive metallic coating. The application of ESEM could have advantages in the study of ceramic samples due to a reduction in preparation time. The microstructures of bulk materials were observed before and after sintering, and the effect of solution processing parameters and the formation of surface defects was studied. Microstructural differences were observed for the same composition materials under the different processing conditions (Fig. 1). The morphological and compositional properties of the final C12A7 samples are highly affected by their structure and crystallisation.
Microstructure of stainless steel produced by direct metal laser sintering
Authors: Labre Cilene , Pinto Andre , Solórzano Guillermo 
Published: December 2016

Microstructure of stainless steel produced by direct metal laser sintering
C. Labre1, 2, A. L. Pinto1, G. Solórzano2

1
Brazilian Center of Physics Research, Rio de Janeiro, Brazil.

2
Department of Chemical and Materials Engineering, PUC‐Rio de Janeiro, Brazil.

Keywords: Additive manufacturing, direct metal laser sintering, 3D
Additive manufacturing or rapid prototyping is a layer‐by‐layer fabrication technique based on selective fusing and consolidating thin layers of loose powders with a scanning laser beam, for building three‐dimensional (3D) objects [1]. Among the various methods of additive manufacturing the direct metal laser sintering (DMLS) had a big progress in the recent years and as an alternative manufacturing route to produce components, it attracted great attention due to the easy processing, high process speed and capability of producing complex shaped metallic objects. The present study focuses on the microstructural characteristics of the 15‐5 PH stainless steel powder and a component built by DMLS from the same powder (composition: Cr 16,4wt%, Ni 4wt%, Cu 3,7 wt%, Mn 1,3wt%, Si 0,045wt%, Mo 0,5wt%, Nb 0,35wt%, C 0,045wt% and Fe (bal.)). For this purpose, JEOL JSM 7100FT scanning electron microscope (SEM), LYRA3 FEG SEM and electron backscattered diffraction (EBSD) have been used at Brazilian Center of Physics Research (CBPF).
Figure 1A shows that the 15‐5 PH powders are in spherical shape and the particle size are in the ranged of 20 to 50μm. Preliminary EBSD results of the slice view of Figure 1B show that the grains are randomly oriented (Figure 1C), each orientation is indicated by a specific color, and it has a higher concentration of grain size of up to 7μm (Figure 1D). Grain orientation map shows that there is not a preferential crystallographic orientation.
Figure 2A shows a SEM image of the cross section of an object produced by DMLS. A laser scanning was repeated to build the subsequent layers until the objects is completed. Arrow indicates the building direction. The grain orientation map presents columnar grains randomly oriented melt pool boundaries (Figure 2B). The grain size distributions show a higher concentration of grain size below 5µm (Figure 1C). The grain size of the object is reduced comparing with the grain size of the original powder.