bluuebunny/crossref_metadata_2025 huggingface dataset:
An approach towards solving
3D
information by combining quantitative
ADF STEM
and
EDX
Authors: MacArthur Katherine , Ozkaya Dogan , Lozano‐Perez Sergio , Nellist Peter
Published: December 2016

Annular dark‐field scanning transmission electron microscopy (ADF STEM) is an invaluable tool for materials characterisation, providing atomic scale information of materials structure and defects. ADF STEM in particular produces images where the intensity contains both composition and thickness information. In fact, through careful quantification of the intensity itself it becomes possible to extract quantitative information and even atom counting. Typically this is either done through comparison with careful standards, comparison with simulations or via statistical methods. For single element nanoparticles it becomes possible to estimate their 3D structure from atom counting and then applying an energy minimisation [1].

Silicon drift detectors (SDDs) have opened up a new era in energy dispersive x‐ray (EDX) microanalysis at the nanometre and even sub‐nanometre scales. The improved detector design allows for larger devices and therefore increased solid angles for x‐ray collection. This provides a significant improvement in x‐ray count rates such that atomic resolution maps and x‐ray tomography are both now possible. In addition, aberration correction in the STEM allows the use of larger probe‐forming apertures to produce increased beam currents in much smaller probes. The combined result provides huge improvements in x‐ray counts from small volumes leading to the potential for improved quantitative analysis at the nanometre scale and below.

In the same way that the scattering cross section, σ, can be calculated from ADF image intensity [2] and for ionisation edges in EELS [3], it is possible to calculate an EDX partial cross section using an approach that demonstrates similarities with the ζ‐factor method [4]. This quantification method was applied to PtCo alloy nanoparticles that have been acid‐leached to provide platinum enrichment (or rather cobalt depletion) at the particle surface. It is possible to quantify the levels of cobalt depletion in the first few atomic layers of the particle, showing that the leaching produces a localised surface depletion that can only be determined by this high resolution EDX quantification [5], [6].

Both of these methods of quantification can be used to yield a range of information about the structure of our material when used individual. Here we look at the potential information which can be achieved through combining the information from each technique. In particular we look at extracting 3D information of bimetallic fuel cell catalysts.
Investigating
Cu
diffusion in
CdTe
solar cells via aberration‐corrected
STEM
:
Cu2
‐
xTe
precipitates at
CdTe
twins and the
CdTe/CdS
interface
Authors: Li Chen , Pennycook Timothy J. , Haigh Sarah , Lupini Andrew , Paudel Naba , Yan Yanfa , Pennycook Stephen
Published: December 2016

CdTe is one of the most promising materials for thin film solar cells due to its near‐optimum bandgap, high efficiency and low cost of fabrication. In order to reduce the contact resistance, it is common to deposit a thin Cu layer at the back of the cell. However, Cu is found to diffuse easily into the p‐type CdTe layer and even to the n‐type CdS layer. This diffusion causes a problem because too much Cu diffusion has been shown to cause performance degradation [1‐2]. Therefore it is important to figure out the pathways of Cu diffusion, and the configurations that Cu stabilizes inside the CdTe solar cells.

In this research, we employed aberration‐corrected Scanning Transmission Electron Microscopy (STEM) combined with Electron Energy Loss Spectroscopy (EELS) or Energy Dispersive X‐Ray Spectroscopy (EDX) to probe Cu diffusion in CdTe solar cells. We first investigated the cells with a typical Cu‐annealing process at 150° C for 45 min in dry air under ambient pressure, but did not find very much Cu diffusion. Therefore we extended the annealing at 150° C for 8 hours in vacuum using our sample‐baking system. The vacuum annealed samples show clear Cu diffusion traces along some of the grain boundaries (GBs). However not all the GBs became Cu‐enriched, indicating that Cu diffusion may have a preference for different GBs (Fig.1). Moreover, STEM‐EDX reveals Cu‐rich precipitates embedded inside high‐density twin boundaries in CdTe (Fig.2). The Cd concentration decreases while Te does not change on the precipitates, and no other elements were found, indicating the precipitates are most likely to be Cu
x
Te
y
. The Cu
x
Te
y
precipitates exist all the way along the high density of twin boundaries from the contact layer to the CdS layer, demonstrating another pathway for Cu diffusion.

Similar Cu
x
Te
y
precipitates were found at the CdTe/CdS interface. A precipitate located at the edge of the STEM specimen without overlapping CdTe or CdS was used to quantify the ratio of Cu to Te via both EELS and Z‐contrast image intensity. Both results show that the ratio of Cu to Te is slightly lower than 2:1, therefore the precipitate can be described as Cu
2‐x
Te. Moreover, the atomic structure of the precipitates show variations from the normal CuTe structure, for example formation of 2×2 supercells (Fig.3). More detailed results will be shown and the photovoltaic behavior of the Cu
2‐x
Te precipitates will also be discussed.
Denoising and compensation of the missing wedge in cryo electron tomography
Authors: Moebel Emmanuel , Kervrann Charles
Published: December 2016

In this study, we have addressed two important issues in cryo electron tomography images: the low signal‐to‐noise ratio and the presence of a missing wedge (MW) of information in the spectral domain. Indeed, according to the Fourier slice theorem, limited angle tomography results into an incomplete sampling of the Fourier domain. Therefore, the Fourier domain is separated into two regions: the known spectrum (KS) and the unknown spectrum, the latter having the shape of a missing wedge (see Figure). The proposed method tackles both issues jointly, by iteratively applying a denoising algorithm in order to fill up the MW, and proceeds as follows:

Excitation step: Add noise into the MW

Denoising step: Apply a patch‐based denoising algorithm

Repeat steps 1 and 2, by keeping KS constant through the iterations

The excitation step is used to randomly initialize the coefficients of the MW, whereas the denoising step acts as a spatial regularization. The employed denoising algorithm, which exploits the self‐similarity of the image, filters out coefficient values which are dissimilar to KS, thereby keeping similar ones. By iterating these steps, we are able to diffuse the information contained in KS into the MW.

An application example on experimental data can be seen on the Figure, which shows the data in both spectral and spatial domain. The data contains a spherical gold particle, deformed by MW induced artifacts: elongation of the object, side‐ and ray‐artifacts. From the residue image it can be seen that noise and MW artifacts have been reduced, while preserving the details of the image. Experiments are being performed to verify if particle detection and alignment are enhanced by using the method as a pre‐processing step.
Plasma cleaning effect on the stability of theEpon resin sections
Authors: Skoupý Radim , Krzyzanek Vladislav , Nebesarova Jana
Published: December 2016

Low voltage TEM and STEM (transmission and scanning transmission electron microscope) can be regarded as the method of choice for many structural studies of very thin biological samples like ultrathin sections, viruses etc. [1]. Unfortunately, the specimen contamination increases with electron flux and therefore a specimen cleanliness is an important factor in obtaining of valuable data especially in STEM [2]. An important parameter for imaging of those samples is a sensitivity of the sample to degradation by electron beam. The mass loss indicates a degree of the radiation damage. We investigated the mass loss of embedding medium (Epon resin of middle hardness) in combination of different thickness of the sections (60 nm and 150 nm) with using or not‐using of plasma cleaning which is often used to removing of contamination from the sample.

The repeated imaging was performed by SEM Magellan 400L (FEI) at the acceleration voltage of 30 kV and the lowest possible probe current of 1.6 pA in the bright field (BF) using the commercial STEM3 detector (FEI). An electron dose for each scan was about 60 e‐/nm2. The measurement was performed at the eighth day after their preparation by the ultramicrotome Leica Ultracut UCT. Some slices were cleaned by Plasma Cleaner (FEI) installed at the Magellan SEM for 20 seconds just before imaging, so they did not leave high vacuum. For each experiment, three different places on each sample were imaged for downgrading space dependency of the measurement. The mass loss was obtained from the normalized BF signals using the Monte Carlo simulation of electron scattering MONCA [3] using the methodology of mass measurements by STEM [4]. All data processing was programmed in MATLAB (Mathworks).

As seen on Fig. 1a, the normalized BF signal (showing the fraction of scattered electron to the BF detector) has similar shape in both thicknesses of the slices without plasma cleaning; the curves are shifted only by the different thickness. However, slices treated with the plasma cleaner show higher sensitivity to incident electron beam with rapidly increasing BF signal; Fig. 1b) shows the remaining mass. At the total irradiation dose of 3000 e‐/nm2there still remains 89% of initial mass for the 150 nm slice and 70% for the 60 nm slice, respectively. However, the slices cleaned by plasma cleaning are much more sensitive to the electron beam, with remaining 55% for the 150 nm slice and local destruction for the 60 nm slice. We observed higher sensitivity of cleaned Epon thin sections under incident electron beam. This limits the usable dose for imaging by the low voltage STEM (for 30 kV) because cleaned sections are more susceptible to burn‐out than non‐cleaned ones.
Analytical electron microscopy of barium titanate and barium‐strontium titanate nanoparticles for second‐harmonic biomarkers
Authors: Matar Omar , Hondow Nicole , Posada Olga , Routledge Michael , Hernandez‐Maldonado David , Wälti Christoph , Murray Claire , Brydson Rik , Milne Steve , Brown Andy
Published: December 2016

Nanoparticles with non‐centrosymmetric crystal structures exhibit second harmonic generation (SHG) of light when illuminated by a femtosecond pulsed laser. Such nanoparticles can be used as optical biomarkers to circumvent the drawbacks associated with fluorescent proteins and semiconductor quantum dots, such as photobleaching and fluorescent intermittency (blinking). Bulk barium titanate has a tetragonal crystal structure at room temperature however, reduction in particle sizes generally correlates with an increasing phase fraction of cubic material which does not exhibit SHG [1].

In this study we have produced barium titanate (BaTiO
3
) and barium‐strontium titanate (Ba
1‐x
Sr
x
TiO
3
) nanoparticles by the hydrothermal method. These nanoparticles appear predominantly cubic by laboratory‐XRD but Rietveld refinement on synchrotron X‐Ray powder diffraction data suggests a mixture of tetragonal and cubic phases. Transmission electron microscopy (TEM) analysis techniques such as electron energy loss spectroscopy (EELS) and energy‐dispersive X‐ray (EDX) spectroscopy have been used to determine the
inter‐
and
intra‐
particle phase and composition of BaTiO
3
and Ba
1‐x
Sr
x
TiO
3
nanoparticles. Prior STEM‐EELS work, suggests an
intra
‐particle phase distribution of cubic and tetragonal phases [2]. STEM‐EEL linescans by aberration corrected scanning transmission electron microscopy (SuperSTEM) confirm that these hydrothermal samples exhibit
intra
‐particle phase distribution of a tetragonal core and a cubic shell (Figure 1 & 2).

Multi‐photon microscopy correlated with SEM demonstrates the SHG signals from the BaTiO
3
and Ba
1‐x
Sr
x
TiO
3
nanoparticles [3]. The cellular uptake and biocompatibility of the BaTiO
3
and Ba
1‐x
Sr
x
TiO
3
nanoparticles have been determined by cell viability (MTT) and genotoxicity (Comet) assays. Uptake was confirmed by backscattered Z‐contrast imaging by SEM and EDX (Figure 3), along with bright field TEM and HAADF‐STEM of resin embedded cell sections. Direct correlation between electron microscopy (SEM & TEM) and multi‐photon microscopy will be used to determine SHG characteristics at the individual particle level when taken up by cells.
Interface migration mechanism on Corundum/Spinel/Periclase: atomic study via aberration‐corrected
STEM
Authors: Li Chen , Griffiths Thomas , Pennycook Timothy J. , Mangler Clemens , Götze Lutz C. , Jeřábek Petr , Meyer Jannik , Habler Gerlinde , Rainer Abart
Published: December 2016

In nature it is common that a new mineral grows between two minerals due to the inter‐diffusion of elements. Understanding its growth mechanism is critical for reconstructing conditions and rates of mineral formation. The growth of the new phase is controlled by the coupling of
interface reaction
and
long‐range diffusion
. To understand the
interface reaction
, it is essential to figure out the atomic structure of the interfaces.

In this research, spinel (MgAl
2
O
4
, Spl) has been grown between periclase (MgO, Per) and corundum (Al
2
O
3
, Crn) via pulsed laser deposition [1] and uniaxial stress methods [2] for studying the early and late growth stages, respectively. Electron Backscatter Diffraction (EBSD) has been used to study the interfacial orientation relationship on both Per/Spl and Spl/Crn reaction interfaces. The EBSD mapping (Fig.1) shows that the Spl layer splits into two different sections: a thinner part in topotaxial orientation relationship with Per, and a thicker part topotaxial with Crn. Then Focused Ion Beam (FIB) was used to lift out the interface areas with representative orientation relationships, and the atomic structure studied by aberration‐corrected Scanning Transmission Electron Microscopy (STEM).

The atomic resolution images of the Spl/Crn interface show that the interface is located where the (001) lattice plane of Crn coincides the (111) lattice plane of Spl, which are both occupied by Al atoms exclusively. In another side, the Per/Spl interface shows a periodic configuration (Fig.2a), consisting of curved segments (convex towards Per) [3]. The image in Fig.2b reveals regularly spaced misfit dislocations at the positions of “cusps” (see the 2D model in Fig.2c), occurring every ~4.5 nm. A similar configuration is observed at another interface area equivalent with a 90° rotation of the structure in Fig.2b. These results unveil the 3D configuration of the interface, which has a grid of convex protrusions of spinel into periclase with misfit dislocation at each minimum (Fig2d). The structure reveals the mechanism of the interface migration: the climb of the misfit dislocations is the rate‐limiting factor and therefore leads to this scalloped geometry. Furthermore, the extra atoms required for dislocation climb leave behind vacancies that eventually form pores at the interface, which provides additional resistance to interface motion and leads to doming of the interface on the scale of individual grains. These results also show that a fundamental understanding of the interface reaction and migration on the atomic scale is the key for understanding the interface migration on the larger scale.
Large area orientation mapping on nanoscale materials using
SEM
Authors: Palasse Laurie , Goran Daniel
Published: December 2016

The increasing interest in nanostructured materials has raised the need for high spatial resolution orientation mapping and large‐scale quantitative characterisation of such microstructures. Because Electron Back Scatter Diffraction (EBSD) does not achieve such high spatial resolution on bulk samples, these kind of studies are often done using a Transmission Electron Microscope (TEM). However, TEM‐based orientation mapping techniques suffer from small field of view. As a result, Transmission Kikuchi Diffraction (TKD) in Scanning Electron Microscope (SEM) was developed as a technique capable of delivering the same type of results as EBSD but with a spatial resolution improved by up to one order of magnitude [1,2]. TKD analysis is conducted on an electron transparent sample using the same hardware and software as for EBSD system. But when using conventional EBSD geometry, the transmitted patterns (TKP) are captured by a vertical phosphor screen with a considerable loss of signal and with strong distortions induced by gnomonic projection. Also, with standard TKD detector configuration, most of the transmitted signal does not reach the phosphor screen and results in lower quality patterns which can have negative effect in the measurement quality.

The limitations of such non‐optimal sample‐detector geometry can be overcome by an on‐axis detection system. With a horizontal phosphor screen placed underneath the sample, the transmitted signal is captured where it is the strongest and TKPs will have minimal distortions. Using low probe currents, the spatial resolution can be increased and the beam‐induced specimen drift reduced as compared to standard TKD detector configuration [3]. The improved stability and high spatial resolution allow the user to conduct large‐area TKD orientation mapping.

Using a partially recrystallized ultrafine stainless steel sample, we will demonstrate that statistical data can be obtained for the quantitative characterisation of nanostructured materials in the SEM (figure 1).
Nanoscale texture analysis of d‐
HDDR
processed
Nd‐Fe‐B
powder particles
Authors: Duerrschnabel Michael , Bruder Enrico , Güth Konrad , Gauss Roland , Gutfleisch Oliver , Molina‐Luna Leopoldo
Published: December 2016

A strong texture in polycrystalline Nd‐Fe‐B powder particles processed by dynamic hydrogenation disproportionation desorption and recombination (d‐HDDR) method is of importance for enhanced macroscopic magnetic properties [1]. This heavily depends on the processing parameters such as the hydrogen partial pressure [2]. The initial and the final step of the HDDR process has already been extensively studied by electron backscatter diffraction (EBSD) technique in the scanning electron microscope (SEM) [3]. However, for SEM‐EBSD analyses, e.g. after the early and full disproportionation step, the spatial resolution as well as the signal of the Kikuchi patterns was not sufficient for a thorough local texture analysis. Therefore, analyses on the nanometer scale have been carried out in a transmission electron microscope (TEM) using orientation and phase mapping via ASTAR/DigiSTAR (“EBSD inside the TEM”). In this case, a spatial resolution of up to one nanometer can be achieved. Data evaluation was carried out using the Matlab® MTEX toolbox yielding, for example, pole figures. Using this technique it is possible to map the phase distribution of α‐Fe, NdH
2
, and Fe
2
B as well as their texture in order to reveal an inter‐phase textural relation during the different HDDR process steps. The current understanding is that solely the Fe
2
B phase is responsible for the texture transfer. The obtained results for the different process steps and parameters will be interpreted with respect to the existing models and the texture analysis results on α‐Fe and NdH
2
from ASTAR/DigiSTAR and EBSD will be compared to evaluate the statistical reliability.
Characterization of nanometric‐sized participates formed during heat treatment of aluminium alloy with antimony
Authors: Matus Krzysztof , Gołombek Klaudiusz , Pawlyta Mirosława
Published: December 2016

New requirements to be met by modern alloys requires changing the currently used materials. This is accomplished by the use of newer and newer generation of production technologies, or by modifying the chemical composition of the alloys presently used. During our research we examined the casting aluminum alloy with the addition of antimony. The chemical composition of the investigated alloys was Mg 5.3‐5.8%, Si 1.7‐2.8%, Mn 0.5‐1.0%, Cr 0.2‐0.6%, antimony content ranged from 0.1 to 0.3%, 0.3‐0.5% 0.5‐0.9% 0.9‐1.2%. Aluminium and antimony form an intermetallic phase AlSb, which serve as the nuclei for crystallization growth of other precipitates, with complex structure and chemical composition. The size of participates that grown on the surface of AlSb is about 10‐15 nm in diameter. Their large concentration and equal, homogenous distribution give the chance to obtain high mechanical properties of investigated material. The aim of the article is characterization of participates formed during age hardening of aluminium alloy with the addition of antimony, as the intermetallic phase component. Structural characterisation of precipitates are made by using simultaneous HR‐TEM and HR‐STEM imaging and EDS analysis. Obtained results were compared with computer simulations.
Preparation and structural characterization of Au nanoparticles supported on metal oxide nanoplatelets for catalysis by a new two‐step method
Authors: Chevallier Virginie , Madigou Véronique
Published: December 2016

While gold has long been regarded as a poorly active catalyst, it is now widely investigated in the field of catalysis and gas sensing. Indeed, it exhibits surprisingly high catalytic activity when deposited as nanoparticles (NPs) on base metal oxides, carbon materials or organic polymers. Especially, gold nanoparticles catalysts with 2 to 10 nm diameters are active for many reactions, such as CO oxidation at a temperature as low as ‐ 70°C. The catalytic performance of supported gold NPs depends on the kind of support materials, the size of gold NPs, and the gold/metal oxide interface structure[1].

A variety of preparation methods (more than 10) have been developed to obtain gold NPs with homogeneous dispersions on supports. Classical chemical methods need a calcination step in order to (i) reduce Au
3+
ions deposited from a precursor (HAuCl
4
is the most popular one) by means of impregnation or deposition–precipitation techniques; (ii) remove organic ligands such as polyvinyl pyrrolidone or polyvinyl alcohol, which prevent the aggregation of gold NPs in the sol‐immobilisation method;(iii) crystallize the metal oxide support in coprecipitation method. During the calcination step, the deposited gold particles generally grow to larger ones, so a precise control of the NPs size is difficult with these methods. On the other side, physical methods (PVD, Cathodic Arc Plasma Deposition) are cleaner and allow precise size distribution of the gold NPs on supporting materials, but they needs specific and expansive devices.

In this work, an original chemical method to prepare gold NPs deposited on a metal oxide is presented. No calcination is required. The gold precursor is HAuCl
4
. The oxide used as supporting material must have a lamellar structure. In this work, we choose an Aurivillius phase (Bi
3.25
La
0.75
Ti
3
O
12
).The preparation consists in two steps. First, lithium is intercalated in the oxide structure, using n‐butyl‐lithium. After washing and drying at room temperature, a stable lithiated compound is obtained, in which some metallic cations have been reduced at a lower oxidation state [2]. Then, the lithiated powder is mixed with a gold precursor in aqueous solution. Gold ions are directly reduced near the support surfaces, without any other reducing agent. and the nanoparticles are formed only atthe oxide surface and they are well dispersed (figure 1). In addition, the NPs formation is accompanied by a partial delamination of the oxide grains which are separated in nanoplatelets (figures 2 and 3).

The materials have been characterized by electronic microscopies (HRSEM, TEM) at each step of the preparation process. The effect of the gold concentration has been investigated and the kinetics of the NPs deposition has been studied by UV‐VIS spectroscopy (figure 4), using the gold NPs localized plasmon surface resonance property.
Modulation of
DAMP
‐mediated
NET
formation by p33
Authors: Neumann Ariane , Papareddy Praveen , Herwald Heiko
Published: December 2016

The formation of neutrophil extracellular traps (NETs) is often associated to entrapment and growth inhibition of several pathogens. However, an excessive NET formation or impaired degradation of the DNA fibres can result in the development of autoimmune diseases, such as SLE or psoriasis. Also NET‐associated molecules, like host defence peptide LL‐37 and cationic histones can have harmful effects. Thus, the host organism needs to rely on precautions to circumvent such deleterious effects.

Our group recently published that p33, a multi‐ligand protein present on several cells types, is able to inhibit the cytolytic activity of LL‐37 on endothelial cells. Additionally, it was found that the application of p33 prevents histone‐mediated platelet aggregation as well as lethal haemolysis in mice treated with histones.

In order to investigate whether p33 plays a role in the formation of NETs, first NETosis was analysed microscopically and biochemically. p33 administration abolished the PMA‐mediated release of DNA fibres and additionally reduced the PMA‐triggered production of ROS. Moreover, both cationic LL‐37 and histones significantly triggered the formation of NETs as well as the release of MPO. However, the simultaneous addition of p33 in a 1:2 ratio decreased the amount of released MPO and the protein‐triggered NETosis. Utilising DNA‐intercalating dye PicoGreen, the effect of p33 on the stabilisation of DNA, backbone of the NET structures, was investigated. Due to their cationic properties, histones as well as LL‐37 bind and protect DNA against bacterial nuclease MN. Interestingly, additional application of p33 diminished the protection of DNA mediated by both LL‐37 and Histones against
S. aureus
nuclease. Taking together, we hypothesise that p33 plays a role in modulating NET induction and NET stabilisation.
Atomic resolution
HR
(S)
TEM
and
EDXS
analyses of
GaInAs/GaSb
and
GaInP/GaSb
bond interfaces for high‐efficiency solar cells
Authors: Kovács András , Duchamp Martial , Predan Felix , Dimroth Frank , Dunin‐Borkowski Rafal , Jäger Wolfgang
Published: December 2016

The use of direct wafer bonding to combine semiconductor materials that have a large lattice mismatch is especially beneficial for high efficiency multi‐junction solar cells. Multi‐junction solar cells that have been fabricated by wafer bonding are of particular interest since efficiencies of up to 46% have been obtained [1] and efficiencies of up to 50% are within reach for concentrator solar cells based on III‐V compound semiconductors. Fast atom beam activation is used as a pre‐treatment to remove oxides and contamination before bonding [2]. Aberration‐corrected transmission electron microsocpy (TEM) analyses of GaAs/Si interfaces have previously been applied successfully to support the implementation of bonding concepts for the development of high‐efficiency solar cells [3].

Here, we investigate cross‐sectional specimens of GaInAs/GaSb and GaInP/GaSb bond interfaces in wafer‐bonded multi‐junction solar cells, in order to obtain an improved understanding of their interface structures and thermal stability, by combining aberration‐corrected high‐resolution TEM (HRTEM), high‐angle annular dark‐field scanning TEM (HAADF STEM), energy‐dispersive X‐ray spectroscopy (EDXS) in the STEM and
in situ
TEM heating experiments.

Figures 1a‐e shows results obtained from the GaInP/GaSb bond interface. Fig.1a shows the interface at low magnification. Figure 1b shows an HRTEM image, which reveals an amorphous interface layer (~1 nm thick). Figure 1c shows an atomic resolution HAADF STEM image of the bond interface structure and a digital diffractogram (inset), revealing a nearly perfect structural orientation relationship between the two crystalline layers. When correctly positioned with respect to the HAADF image, elemental maps extracted from EDXS spectrum images (Figs 1d and 1e) reveal that a high level of Ga is present at the interface. The Ga can be attributed to the pre‐treatment procedure and bonding conditions.
I situ
thermal treatment of this interface results in pronounced interdiffusion for temperatures above 225°C (not shown here).

Figures 2a‐c show the GaInAs/GaSb bond interface, which is decorated by pores and cavities that extend along the interface by more than 10 nm. As a result of the use of misoriented wafers for bonding, the crystal lattices are rotated with respect to each other by a few degrees (Figs 2b and 2c).

Our results confirm that the advanced imaging and spectroscopic methods of aberration‐corrected (S)TEM are advantageous for characterizing the morphology, elemental distribution and structure of layers and bond interfaces for the monitoring, control and optimization of different concepts used for fabricating high‐efficiency solar cells. Out results are also of interest for assessing electrical conductivity phenomena at these interfaces.
Mycobacterial protein weaponry studied by cryo‐correlative microscopy
Authors: Notelaers Kristof , Berger Casper , Iakobachvili Nino , Chen Delei , Siroy Axel , Furusho Hirotoshi , Ravelli Raimond , López‐Iglesias Carmen , Peters Peter
Published: December 2016

In correlative light and electron microscopy, the discerning power of fluorescence microscopy (FM) is combined with the ultra‐high resolution of electron microscopy (EM). We fluorescently label protein complexes in cells, with the purpose of facilitating their identification in transmission electron tomograms. Our imaging strategy is to perform cryogenic selected volume tomography, continuously keeping the specimen in a vitreous state. To this end, we are developing a cryogenic workflow in collaboration with FEI, consisting of three microscopes: CorrSight light microscope (LM), Scios Dualbeam scanning electron microscope (SEM) with a focused ion beam (FIB) and Tecnai Arctica cryo–transmission electron microscope (TEM). The focus of my presentation is on the integration of the CorrSight light microscope into the workflow (1). This translates to performing cryogenic light microscopy and correlating the images with EM for guided ion beam milling and tomography (2).

The data we collected from cryogenic fluorescence microscopy of mammalian and bacterial cells on TEM grids shows great promise for complementing EM (Fig. 1). This is substantiated by alignment of LM and SEM images utilizing FEI MAPS software, allowing for fluorescence based navigation during SEM imaging (Fig. 2). My future efforts will focus on improving localization precision and correlation accuracy, to guide FIB‐milling of sub‐cellular structures in the SEM. FIB‐milling is used to fabricate thin lamellae in cells, making them suitable for cryo‐TEM. Our results indicate that tomograms can be recorded from lamellae using a 200kV cryo‐TEM, but vitrification of the specimen is essential. The ultimate goal of our workflow is to obtain structural insight of the Type 7 Secretion System (T7SS), formed by the ESX‐1 machinery. To this end, we will perform tomography of mycobacterial membranes inside professional antigen‐presenting cells. The T7SS is an important part of the mycobacterial protein weaponry, as it mediates virulence and phagosomal escape (4, 5).
EBSD
Analysis of the Microstructural Evolution of
N
i‐Superalloys
Authors: Godec Matjaž , Burja Jaka , Podgornik Bojan , Tehovnik Franc
Published: December 2016

Ni‐superalloys are well known for their high strength, outstanding corrosion resistance and their resistance to both fatigue and creep, As a result, they are frequently used in gas‐turbine and aero‐engine applications. Inconel 625 also has a high resistance to chloride‐ion stress‐corrosion and is used in very aggressive environments. The strength of Inconel 625 is derived from the stiffening effect of molybdenum and niobium on its nickel‐chromium matrix; thus precipitation‐hardening treatments are not required. Control of the microstructure is very important with respect to the mechanical properties of the material. The microstructure changes during the hot rolling of the Inconel nickel‐chromium superalloy 625 were investigated using FEG SEM. A detailed insight into the recrystallization behaviour during hot rolling was provided by an EBSD analysis (Figure 1). During the hot rolling the recrystallization starts on the grain boundaries, followed by the twin grain boundaries and, at even higher stresses, the recrystallization occurs on the (TiNb)CN phases inside the crystal grains. The EDS and EBSD results were able to explain the complex nature of the (TiNb)CN phases.
Turning Off Photoinduced Electron Transfer In Green Fluorescent Proteins For Super‐Resolution Microscopy
Authors: Mamontova Anastasia , Bogdanov Alexey , Mishin Alexander , Klementieva Natalia , Lukyanov Konstantin
Published: December 2016

Under blue light irradiation green FPs can act as light‐induced electron donors in photochemical reactions with various electron acceptors. These reactions are accompanied by green‐to‐red photoconversion (oxidative redding) which is among the processes significantly contributing to the photostability of many GFP family proteins. We suppose that inhibition of redding will have similar consequences in super‐resolution microscopy (PALM) as it does in epifluorescent microscopy, namely, enhanced photostability and average fluorophore brightness. Understanding of the primary mechanisms of electron transfer (ET) occurring in excited state allows to control the photostability. In our recent work [1] we consider two mechanistic hypotheses:

ET proceeds via direct ET to a surface‐docked oxidant (tunnel mechanism)

Photoinduced ET proceeds via a hopping mechanism (in which the first step is ET from the chromophore to some intermediate acceptor, and the second step is ET from this acceptor to an outside oxidant molecule)

Hopping mechanism appears to be the most likely process according to the quantum‐mechanical calculations. One of the approaches to reduce ET via hopping mechanism is an elimination of the potential internal electron acceptors, located in the side chain of fluorescent protein. We determined such critical residues in the polypeptide chain of PAGFP using quantum‐chemical simulations, and changed them to amino acid that is not able to be an efficient electron acceptor, namely, leucine. According to both epifluorescent and TIRF‐experiments' data, this substitution leads to the highly improved photostability in comparison with the original PAGFP. It has also been shown that in TIRF‐experiments PAGFP Y145L had significantly lower blinking rate than PAGFP (see Fig.1). This property could be potentially used in SPT (single particle tracking) technique, where transitions to the dark states impose serious constraints and appear to be a drawback.
Investigation of structural changes of
ZnO:Ti
thin films prepared by
RF
sputtering
Authors: Medlín Rostislav , Sutta Pavol , Netrvalova Marie , Novak Petr
Published: December 2016

ZnO is a wide used ferroelectric material with a variety of applications. This study investigates ZnO thin films doped by Ti as showing structure change from ZnO wurtzite up to ZnTiO
3
perovskite.

ZnO:Ti thin films were prepared by RF reactive magnetron co‐sputtering in Ar/O
2
atmosphere from pure Zinc and Titanium targets (99.99%). Changes of amount of Ti in films were documented by EDS and EELS measurements, structure changes were measured by electron diffraction from thin film cross section (XTEM ED) and two geometries of XRD together with measurement of material optical properties.

Pure ZnO wurtzite structure show with increasing amount of Ti texture change from 8 degrees for 2.4 at % Ti to the 39 degrees for 8.7 at % Ti as it can be seen on electron diffraction patterns on figure 1a together with figure 1b. Structure measured by XRD appear to be more amorphous with Ti increasing as intensity of diffraction lines decreases and interatomic distances change from wurtzite to perovskite ZnTiO
3
structure (fig. 2).

Diffraction measurement is by the Voight function method also capable to measure from single diffraction line size and lattice distortions of the diffracted particles. In our case results for 2.4 at % Ti ZnO line 002 is 52 nm and for 7.8 at % Ti ZnTiO
3
line 104 is 19 nm, both with dualism indicates two regions of low and highly distorted part of particles. This correspond to relaxed core and distorted surface of the grains as it can be seen on figure 1c and d for Ti content 2.4 at % Ti or 8.7 at % Ti respectively.

Electron diffraction pattern from cross section is also capable to show and compare information from XRD measurements in two different geometries; situation is illustrated on figure 3. Circle integration of ED by ProcessDiffraction program [1] is capable to compare JCPDS diffraction database with electron diffraction pattern, however, this procedure do not take into consideration texture of investigated materials. Different geometries of XRD measurement takes in case of textured material different places indicated on XTEM electron diffraction pattern on Fig.3. Comparing of both results have to be carefully considered.

Direct comparation of measured interplanar distances is illustrated in Fig.4.
Synthesis and characterization of bimetallic nanorods
Authors: van der Hoeven Jessi , Albrecht Wiebke , Deng Tiansong , de Jongh Petra , van Blaaderen Alfons
Published: December 2016

Anisotropic metal nanoparticles (NPs), and especially nanorods (NRs) exhibit interesting optical properties, which arise from their localized surface plasmon. Unlike nanospheres, gold NRs have a longitudinal surface plasmon resonance (LSPR) in the visible or near‐infrared range of the spectrum. By altering e.g. the shape or the dimensions (aspect ratio) of the NRs, the LSPR can be tuned, which makes them interesting materials for a broad range of light based applications, such as photocatalysis [1], data storage [2] and photothermal applications. The optical properties of gold nanoparticles can be extended even further by introducing a second metal. However, synthesizing bimetallic NRs with a good control over the metal composition and distribution while retaining the rod shape is challenging.

In this study we present bimetallic systems composed of gold‐based NRs coated with a protective mesoporous silica layer. We show that it is possible to synthesize bimetallic core‐shell nanorods within a mesoporous silica shell, by etching away part of the gold and overgrowing the remaining Au‐core with a second metal while precisely controlling the core‐size, metal‐shell thickness and thus the metal‐to‐metal ratio [3]. Depending on the choice of metal, different growth behavior was observed. Overgrowth with Ag resulted in a smooth shell whereas the Pt and Pd metal shells had a rough morphology (Figure 1). The different types of bimetallic NRs were characterized in detail with advanced electron microscopy techniques such as Energy‐dispersive X‐ray spectroscopy (EDX), high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and electron tomography. Subsequently, we used these silica coated bimetallic core‐shell structured rods as a starting material to make fully alloyed NRs, whereby the two metals were mixed via thermal treatment without loss of anisotropy [4]. The alloying process was followed in detail with in‐situ HAADF‐STEM heating and EDX measurements by making use of a special heating holder (Figure 2).
Complex magnetic distribution of diameter‐modulated
FeCoCu
nanowires resolved by Electron Holography
Authors: Rodríguez Luis Alfredo , Bran Cristina , Reyes David , Gatel Christophe , Berganza Eider , Vázquez Manuel , Asenjo Agustina , Snoeck Etienne
Published: December 2016

In the last years, diameter‐modulated (D‐M) ferromagnetic nanowires (NWs) have been intensively studied to evaluate their efficiency to control the motion of domain walls (DWs) along these one‐dimensional nanostructures by the application of magnetic field or the injection of electrical current, which is essential for spintronic applications in the field of information storage, sensors and logical operations [1]. Preliminary studies in D‐M NWs have been performed using theoretical and experimental procedures [2‐4] in individual and isolated NWs and they have provided a first approach of the spin configuration in these systems, obtaining a non‐trivial interpretation.

In this work, we have exploited the potential of electron holography technique (high spatial resolution, high sensitivity and quantitative capability in volume) for achieving a full picture of the magnetic distribution in cylindrical D‐M FeCoCu NWs. These NWs were prepared by filling self‐assembled cylindrical D‐M nanochannels of anodic aluminum oxide templates. The D‐M geometry of the polycrystalline NWs consist of alternating segments of small (100 nm) and large (144 nm) diameters, with segment lengths ranging between 1000 to 300 nm. At remanence, the high‐shape anisotropy of the NWs induces a single‐domain state where the spins are mainly oriented along the NW axis, with the possibility to create a small closure domain in large‐diameter tips. The transition zones where the diameter is varied induce a complex demagnetizing field where the stray field follows a flux‐closure configuration around the large‐diameter segments and a magnetic coupling between them around small‐diameter segments (See Fig 1). The complex configuration of the demagnetizing field can be understood if we treat the D‐M transition zones as magnetic charges. The interpretation of the magnetic distribution by EH experiments was compared with micromagnetic simulation finding a very good agreement (see Fig 2). In addition,
In‐situ
Lorentz microscopy experiments of the magnetization reversal process allowed evaluating the DW nucleation and propagate process by the application of magnetic fields. We found that a field‐driven manipulation of DWs is not possible for the NWs in study. This “unsuccessful” result however helps us to take a step forward for the optimization of the geometry to reach the desired DW manipulation.
Female germ‐line cyst composition and functioning in the sludge worm Tubifex tubifex (Tubificinae)
Authors: Urbisz Anna , Chajec Łukasz , Świątek Piotr
Published: December 2016

The single female germ‐line cyst constitutes the whole ovary in
Tubifex tubifex
. The cyst is polarized and germ cells in the consecutive stages of oogenesis are localized along their long axis. The entire cyst consists of more than 2 000 germ cells. As oogenesis progresses, clustered germ cells differentiate into two morphologically distinguishable categories – the smaller but more numerous nurse cells and only eight growing oocytes at a time on average. During oogenesis, the oocytes gather organelles and storage material, i.e. lipid droplets, glycogen granules and protein yolk and grow considerably on the one side of the ovary in a linear arrangement. Vitellogenic oocytes lose their connections to the ovary and are released into the body cavity.

The spatial organization of germ‐line cysts in
T. tubifex
is broadly similar to the other clitellate annelids known to date, and each cyst is composed of two elements – 1) a common and anuclear cytoplasmic mass (cytophore), which in
T. tubifex
is long and branched and snakes back and forth within a cyst and 2) germ cells located on the cytophore periphery. Each germ cell is connected to the cytophore by one stable intercellular bridge (ring canal). A rich cytoskeleton was observed within the cyst, which was mainly an inner microfilamentous rim of ring canals, prominent strands of actin filaments within the cytoplasm of the cytophore and a dense microtubular network that filled the cytoplasm of the germ cells and cytophore. Using the techniques of life cell imaging, experiments with cytotoxic substances that inhibit cytoskeletal polymerization and SBEM methods (Serial block‐face scanning electron microscopy),we attempted to study the formation and functioning of germ‐line cysts and the role of the cytoskeleton. It appears that the cytoskeleton within the germ‐line cysts of
T. tubifex
plays an active role in maintaining the integrity of the huge and multicellular syncytium and takes part in the cytoplasmic transport of organelles and macromolecules from the nurse cells via the cytophore towards the growing oocytes.
Three dimensional confocal imaging using coherent elastically scattered electrons
Authors: Zheng Changlin , Zhu Ye , Lazar Sorin , Etheridge Joanne
Published: December 2016

To fully understand structure‐property relationships in nanostructured materials, it is important to reveal the three dimensional (3D) structure at the nanometre scale.

Scanning electron confocal microscopy (SCEM) was introduced as an alternative approach to 3D imaging in 20031. The confocal method was originally developed in optical microscopy to image the 3D structure of biological samples2. The incident beam is focused at a certain depth in a thick sample, and the excited fluorescence signal is imaged onto the detector plane through the imaging system. A small pin hole before the detector only allows the signal from the confocal plane to reach the detector and blocks the out‐of‐focus signal. Critically, by using a fluorescent signal, the incident and outgoing waves lose their phase relationship and an incoherent 3D point spread function can be achieved.

The optical setup in SCEM is analogous to fluorescence confocal microscopy and also requires an incoherent signal to achieve the incoherent 3D point spread function. Several groups have developed different approaches to using inelastically scattered electrons to achieve an incoherent confocal condition in the TEM3,4,5, however, difficulties remain. Core‐loss electrons have a suitably limited coherence length, however, the excitation probability is extremely low which leads to a poor signal to noise ratio (SNR). Low loss electrons give a much better SNR but still have a significant coherence length due to the collective nature of the excitation.

In this work, we introduce a different approach to achieve 3D imaging in a confocal mode by using the elastically scattered, coherent electrons. This method exploits the depth sensitivity of electrons that have suffered a specific momentum change, rather than an intensity change. According to Fourier optics, when a thin object is inserted at a distance z above the confocal plane, the new wave function at the confocal plane will be the original probe convoluted with the Fourier transform of the object function, together with a scale factor related to z (defined in fig.1). For crystalline specimens, the Fourier transform of the object function is a set of delta functions, so a diffraction‐like pattern will be generated at the confocal plane. Importantly, the separation between the diffraction spots is proportional to the distance z (see fig.1), so that the resulting diffraction contrast is very sensitive to depth. This strong depth sensitivity is combined with the very strong SNR due to the use of the elastically scattered signal. Applications to the imaging of 3D engineered nanostructures are demonstrated (fig. 2 and 3).