bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soft matter, and the many flavours of diffraction tomography
Authors: Stewart Andy 
Published: December 2016

With the arrival in 2009 of diffraction tomography for crystal structure solution [1] of sub‐micron sized crystals, there has been a renaissance in the application of electron diffraction, with diffraction tomography providing a relatively easy path to quantitative analysis of crystal structures, compared to more conventional electron diffraction approaches. The collection of diffraction tomography data occurs by tilting the crystal around an arbitrary axis, which runs counter to the traditional notions of electron diffraction from low index orientated zones. Given the success of the method, it has produced a series of derivative techniques on this theme, of collecting tomographic diffraction from around an arbitrary axis. Each of these methods comes with its strengths and weaknesses.
An investigation into the relative merits of the various diffraction tomography techniques, ADT[1], RED[2], EDT[3], Rotation method[4], MicroED[5]. With an emphasis on the application of the techniques for soft matter and radiation sensitive materials, such as organic and protein crystals. Evaluation of the nuances in data collection strategies, hardware requirements, specimen requirements, and optional components, will all be considered, with details of how they affect the experimental setup, data acquisition, and processing.
We will discuss the need for validation of structural models and the added difficulties presented in doing so with soft matter materials, often leading to the requirement of validation by additional techniques.
An in situ multiscale approach for the characterization of plasticity and damage in a
TA6V
alloy
Authors: Cazottes Sophie , Dancette Sylvain , Bourlot Christophe Le , Maire Eric , Paris Thomas 
Published: December 2016

Due to its specific strength and good biocompatibility, Ti‐6Al‐4V alloy find many applications in medical and aeronautic industries.
At room temperature, the studied TA6V alloy presents a bi‐modal microstructure consisting of hcp alpha phase together with bcc beta phase. When subjected to high cooling rates such as in welding processes, a lamellar hcp alpha' phase appears, which modifies the plastic and damage behavior of the alloy. In order to better understand the role of microstructure on failure of the material, a clear connection must be made between microstructural parameters such as interfaces, grain or lath orientation, grain boundaries, morphologies and failure initiation.
The deformation behavior of both welds and base metals were characterized by in situ EBSD tensile tests. Slip and twin systems were identified for bimodal and fully martensitic microstructure. Deformation paths were followed upon deformation, and related to original laths or grain orientation, see Figure 1. At higher deformation levels, damage starts and cavity appear equally at grain boundaries, phase boundaries, or inside grains. However, if a large number of information is available from these 2D observations, 3D characterization is required for a quantitative damage study as most of the cavities initiate in the volume and not at the surface. The same samples were then characterized by in situ tensile X Ray Tomography tests conducted at ESRF Grenoble.
For several deformation levels, a quantification of the cavity number and size was performed and a clear description of the cavity initation, growth, and coalescence was obtained in 3D, as reported on Figure 2.
Lanthanide distribution in
NaLuF4:Gd,Yb,Er
upconversion nanocrystals by
EFTEM
and
EELS
Authors: Lu Elsa , Pichaandi Jothirmayanantham , Tong Lemuel , Winnik M. A. 
Published: December 2016

Lanthanide‐doped nanoparticles (NPs) have gained interest within the last decade due to their photon upconversion properties. Upconversion is a multi‐photon process in which two or more lower energy photons are converted to a higher energy photon by step‐wise energy transfer between an absorber ion and an emitter ion (1). These upconversion nanoparticles (UCNPs) are a promising alternative to traditional organic fluorphores and quantum dots in the area of bioimaging because their excitation wavelength (980 nm) lies within an optical window where there is the least absorption and scattering by biomolecules (lower background signals), and they do not exhibit photobleaching or photoblinking.
One of the main challenges limiting their application is a trade‐off between luminescence intensity and size of the NP. Smaller NPs exhibit less toxicity as they can be excreted through the urinary system, and they are better for intracellular imaging as the smaller size prevents interference with molecular trafficking within the cell, pharmacokinetics, and protein function; however, upconversion luminescence intensity decreases with size due to, in part, surface quenching from the presence of surface defects (2).

Few reports exist on the synthesis of sub‐10 nm UCNPs, and even fewer exist on the synthesis of sub‐5 nm UCNPs that show visible upconversion emission (3‐6). We have recently synthesized two sizes of NaLuF
4
:Gd, Yb, Er UCNPs (ca. 4 nm and ca. 12 nm), through a facile one‐pot method, that both show bright upconversion luminescence upon excitation by a 980 nm laser.

In order to better understand their luminescent properties, we have used energy filtered transmission electron microscopy (EFTEM) and electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy (STEM) to investigate the distribution of the different lanthanides within the nanocrystal. Measurements were performed on an HF‐3300 instrument operating at 300 kV.
The results suggest that Lu is enriched in the outer (shell) region of the nanocrystal, while Gd is enriched in the inner (core) region of the nanocrystal (Figure 1). Based on these results, we propose that the Lu shell protects the upconverting core from surface quenching, thereby allowing even 4 nm NPs to show upconversion luminescence. We also propose that the formation of the core‐shell structure is mediated by the way the individual lanthanides nucleate in solution – Gd nucleates first to form the core, while Lu nucleates later to form the shell. This proposal is also in accordance with previous reports on the nucleation of lanthanide NPs (7).
EFTEM and EELS in STEM are shown to be valuable tools to characterize the structure of lanthanide‐doped UCNPs and to determine structure‐property relationships, and can aid in the further development of these materials for various applications.
Analytical electron microscopy characterization of light‐emitting diodes based on ordered
InGaN
nanocolumns
Authors: Torres‐Pardo Almudena , Gačević Žarko , García‐Lepetit Noemi , Müller Marcus , Metzner Sebastian , Bengoechea‐Encabo Ana , Albert Steven , Bertram Frank , Veit Peter , Christen Juergen , Calleja Enrique , González‐Calbet Jose M. 
Published: December 2016

Self‐assembled nanocolumns (NCs) with InGaN/GaN disks constitute an alternative to conventional light emitting diodes (LED) planar devices [1]. However, their efficiency and reliability are hindered by a strong dispersion of electrical characteristics among individual nanoLED. Polychromatic emission derives from an inhomogeneous distribution of indium concentration due to the inherent tendency of InGaN alloys to develop composition fluctuations as a function of the polarity of the growth crystallographic planes [2]. The recent development of selective area growth of NCs by molecular beam epitaxy has allowed the achieving of highly homogeneous and controllable GaN/InGaN NCs with improved crystalline quality and higher control over the indium distribution [3].
In this work, we present the characterization performed on LEDs based on ordered NCs with InGaN active disks (figure 1). The detailed structural characterization of the nanostructures has been performed by scanning transmission electron microscopy (STEM) carried out on an aberration‐corrected JEOL‐JEMARM200 microscope. High crystal quality of the NCs is set by the analysis of atomically‐resolved high angle annular dark field (HAADF) images. The indium distribution within the InGaN disks is studied by EDS elemental mapping while the polarity of the semiconductor NCs is followed by locating the nitrogen atomic columns in annular bright field (ABF) images while (figure2). Direct correlation of the optical and structural properties on a nanometer‐scale was achieved using low temperature cathodoluminescence (CL) spectroscopy in an FEI STEM Tecnai F20 [4].
Multi‐color correlative PALM/STORM and electron tomography reveals micro‐domain organization of endosomes
Authors: Brouilly Nicolas , Kalaidzidis Yannis , Verbavatz Jean‐Marc , Zerial Marino 
Published: December 2016

Correlative Light and Electron Microscopy (CLEM) is a method of choice to demonstrate the localization of a protein in a given organelle while revealing the ultrastructure of the organelle. However, a long‐lasting problem in CLEM is the mismatch of resolution between modalities. As it becomes more and more clear that most organelles show a sub‐compartmentalization of their membranes into distinct micro‐domains, the visualization of such micro‐domains at the molecular level using CLEM is a potential strategy to elucidate the molecular basis underlying the ultrastructure of organelles.
We developed a workflow that combines multi‐color Single Molecule Localization Microscopy (SMLM) and electron tomography on the very same sample. We applied this approach to study the compartmentalization of early endosomes in micro‐domains. As proof of principle, we visualized Transferrin and EGF as models of cargo molecules that follow the recycling and degradative route, respectively. Using single molecule CLEM tomography, we could visualize Transferrin and EGF molecules in distinct morphological compartments within the same endosome (see figure). We could also demonstrate the localization of Rab5 in micro‐domains on the globular membrane of the endosome and its exclusion from the tubular parts. Beyond endocytosis, this method can be applied to any biological question requiring both multi‐molecule nanoscale localization and 3D ultra‐structural information of the very same sub‐cellular structure.
Revealing nanoscale morphology of organic solar cell blend by analytical electron microscopy
Authors: Sedighi Mona , Löffler Markus , Zschech Ehrenfried 
Published: December 2016

Organic photovoltaic as future technology with cost‐efficient production and printability is a promising research field. New materials and studying improved synthesis techniques over the past years lead to efficiencies of more than 13 % by organic solar cell [1]. In order to improve device efficiencies, the conversion rate of photo‐generated excitons to electron‐hole pairs should be increased. This critical aspect, depends on the complex morphology of distributed donor and acceptor materials.

In this work we resolve the morphology of an organic solar cell, where the active layer is a blend of two small molecules; ZnPc (ZnC
32
H
18
N
8
) as donor and C
60
as acceptor
.
The investigation of nanoscale morphology and phase distribution is conducted using Energy Dispersive X‐ray spectroscopy (EDX) and Energy selective Backscattered (EsB) imaging in SEM [2]. The results are confirmed using analytical TEM.

The unique aspect of this work is substituting complicated TEM method by SEM with these advantages:
• Possibility of resolving chemical composition in a real solar cell in contrast to commonly deposited blend layer on TEM grids, that allows to study the complete stack of glass substrate, Indium tine oxide (ITO) electrode, electron and hole transport layers and aluminum top electrode.
• No influence of thick (90 nm) layer of heavy ITO, which is under the donor acceptor blend layer, on the TEM study.
• Gaining insight into the height distribution and roughness beside the lateral distribution (as in TEM)
To correlate morphology and material contrast we combined EDX data of the pure materials (composition of specific structure) with EsB detector mapping (strong contrast, unknown corresponding material). EDX spectrum of two material phase is shown in Figure 1, the same features where imaged by EsB detector, as it can be seen in Figure 2. Taking advantage of this combined data, we overcome poor EDX lateral and depth resolution. Since exciting Zn‐K using high energy electrons, deteriorates the spatial resolution and damage the material.
Furthermore, we manage to observe the phase morphology, despite the very close mass average and quite similar chemical composition of the two phases.
In principle the technique can be extended to 3D mapping by use of slice‐and‐view approaches. Finally, our analytical TEM (EELS and EDX) investigations proved the corresponding morphology of each phase.
Ion implantation into two‐dimensional materials for electronic tailoring ‐ observing the behaviour of individual implanted atoms
Authors: O'Connell Eoghan , Kardynal Beata , Tu Jhih‐Sian , Winkler Florian , Hofsaess Hans , Kepaptsoglou Demie , Ramasse Quentin M. , Amani Julian Alexander , Zan Recep , Bangert Ursel 
Published: December 2016

Controlled manipulation of materials on the atomic scale is a continuing challenge in physics and material science. Doping of two‐dimensional (2D) materials via low energy ion implantation could open possibilities for fabrication of nanometre‐scale patterned devices, as well as for functionalization compatible with large‐scale integrated semiconductor technology. High resolution imaging and spectroscopic analysis of these electronic dopants at the atomic scale is fundamental for understanding sites, retention, bonding and resulting effects on Fermi level shifts. This has been made achievable with the advent of aberration corrected transmission electron microscopy (TEM) and scanning TEM, as well as low‐loss electron energy loss spectroscopy (EELS).
We show for the first time directly that 2Ds can be doped via ion implantation. Retention is in good agreement with predictions from calculation‐based literature values [1], as are initial results of the sites of dopants and their influence on the band structure of surrounding atoms. We present results of N‐ and B‐implantation in graphene [2,3] as well as current progress with ion‐implantation in TMDCs.
STEM
optical sectioning for imaging screw dislocation core structures
Authors: Hernandez‐Maldonado David , Yang Hao , Jones Lewys , Gröger Roman , Hirsch Peter B , Ramasse Quentin M , Nellist Peter D 
Published: December 2016

The introduction of spherical‐aberration correctors in STEM has allowed an improvement in spatial resolution up to the sub‐angstrom scale also accompanied by a reduction of the depth of focus (due to the increase in probe convergence angles), which in a modern instrument is just a few nanometers, thus often less than the sample thickness. This can be exploited to extract information along the beam direction by focusing the electron probe at specific depths within the sample. This technique has already been used to observe the depth‐dependence of the strain field due to the Eshelby twist associated with dislocations containing a screw component in thin STEM samples. The measurement of the magnitude of the displacement confirmed the screw Burgers vector for dislocations in GaN [1] and allowed the identification of a new dissociation reaction associated with mixed [c+a] dislocations [2]. The optical sectioning approach has also been applied to the direct observation of the c‐component of the dissociation reaction of a mixed [c+a] dislocation in GaN by imaging a dislocation lying transverse to the electron beam [3].
Here we show how optical sectioning in high‐angle annular dark‐field (HAADF) STEM imaging conditions can be used to image the core structure of screw dislocations at atomic resolution. In particular, we evaluate using simulations whether the edge and screw displacements associated with the delocalization of ½[111] screw dislocations in body‐centered cubic (BCC) metals [4] can be detected. In Figure 1 we show that the helicoidal displacements around a screw dislocation can be imaged with the dislocation lying transverse to the electron beam by optically sectioning the plane containing the dislocation.
In order to reveal how the edge components of the dislocation contribute to the observed contrast we have created two atomistic models, one using the anisotropic linear‐elastic displacements around the dislocation, which is not capable of modelling the core delocalisation, and the other using the core structure relaxed using the Bond Order Potential for W which does predict a delocalised core. Figures 2 a) and b) show the respective HAADF simulated images. Figure 2 c) is the RGB image made from the (101) component of the Fourier Transform (FT) (shown in Figure 2 d)) of both images. It is possible to observe that the shifts in this Fourier component occur along two distinct lines lying parallel to [111]. The superposition of both filtered images shows that there is a discrepancy on both sides of the core between both models. It is therefore apparent that the delocalisation of the core can in principle be detected using electron‐optical sectioning [5,6].
Time‐resolved cathodoluminescence in a scanning electron microscope
Authors: Meuret Sophie , Zeijlemaker Hans , Neu Elke , Appel Patrick , Maletinsky Patrick , Polman Albert 
Published: December 2016

The past decade has witnessed enormous progress in the design and fabrication of nanostructured materials with unique optical properties. These tiny physical structures allow geometrical control over the electromagnetic shape of light well below its own wavelength. A large variety of applications for this field of subwavelength optics known as nanophotonics have already begun to emerge, including solar photovoltaics, chemical sensing, quantum cryptography, and LED lighting. Many fundamental optical interactions are hidden beneath the diffraction limit, however, which makes the retrieval of subwavelength optical behavior impossible with standard microscopy. An alternative approach, known as cathodoluminescence (CL) [1], is to probe nanostructures with an electron beam, which excites optical resonances and transitions and then collects the emitted light. It has recently been used to characterize plasmonic structure [2] or III‐N heterostructures [3]. Thanks to a very efficient CL system, in a scanning electron microscope (SEM), working in free space, we can directly probed many key dimensions of light – including intensity, angle, polarization, and frequency – with ~10 nm resolution [4].In this presentation we will show how we can use a blanker to modulate a continuous electron beam to generate electron pulses with a resolution of ~10 ns. This approach has several advantages compared to alternatives such as a laser driven pulsed electron gun [5]. It can be easily implemented in any SEM, it requires few experimental modifications, it does not require a dedicated microscope and the pulsed electron beam can be controlled at will (pulse duration and repetition rate). We will show how this pulsed electron gun can be used to explore the dynamics of a single photon emitter, such as a rare earth ion or the NV0center of nano‐diamond. An HBT interferometer allows recording of the autocorrelation function of the CL signal [6][7]. Combining secondary electron images with measurements of the CL spectra, emission polarizations, lifetimes and second order correlation function, we are able to fully characterize optically active systems at the nanometer scale.
A protected inert‐gas sample manipulation and transfer environment for cryo electron microscopy and analytics
Authors: Alexander Rosenthal Georg , Tacke Sebastian , Lucas Falk , Wepf Roger Albert 
Published: December 2016

The preservation of the native sample state during manipulation and exchange between sample preparation and imaging devices is a prerequisite for artefact and contamination free structure investigation. In particular during cryo‐transfer and (re‐)mounting of frozen hydrated samples, which often in electron microscopy (EM), have a very large surface area compared to its volume, can be very challenging when samples have to be exchanged or remounted several times. Some of the main challenges are: 1. preventing the sample from warming up to the de‐vitrification temperature of water (approximately −137°C), 2. Preventing the sample from being covered with ice or other contaminants condensing from the surrounding atmosphere and 3. Handling these samples without chemical or mechanical alteration of their native state.
Currently the handling and transfer of samples under vacuum and cryo conditions is solved by systems provided from different suppliers. However the transfer of frozen (vitrified) samples under environmental pressure (e.g. from a high‐pressure‐machine to a low temperature coater or cryo‐EM) is still a challenge and a satisfactory practical solution is missing.
Here, we present an ambient pressure inert‐gas sample mounting and exchange chamber (Glove‐Box) (Fig. 1 &B) that addresses all the needs for structure and composition preservation during the manipulation, mounting and transfer of mainly frozen or hydration/oxygen sensitive samples. Once mounted these samples can be transferred and exchanged between different cryo‐preparation and imaging systems (Fig. 1 E) under controlled inert‐gas and temperature conditions. This controlled inert‐gas “Glove‐Box” includes a LN2 immersed sample mounting area with various interfaces to different inert‐gas/cryo transfer systems for RT or low temperature TEM or FIB/SEM applications, Furthermore, monitoring of the environmental parameters (Fig. 1 C) during transfer (humidity, oxygen, carbon dioxide), on‐screen imaging to support sample manipulation (Fig. 1 D), heating of tools and recording of all experimental parameters for documentation are included into this dedicated LN2 and inert‐gas “Glove‐Box”. The interface to other sample carrier devices is open and flexible and can be adapted upon individual laboratory needs. Finally such a “Glove‐Box” can play an essential role in a dedicated modern cryo‐EM & analytical environment as sketched in Fig. 1 E.