bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect on the
SEM
topography of different sample preparation methods for thin‐film‐composite membrane
Authors: Huang Wenqing , Miao Xiaopei 
Published: December 2016

Thin‐film‐composite (TFC) membrane was prepared through interfacically polymerizing m‐phenylene‐diamine (MPD) and trimesoyl chloride (TMC) on top of a poly‐sulfone substrate to form an ultrathin active polyamide layer, which is excellent in hydrophilicity, mechanical stability, thermal stability and hydrolytic stability. Scanning electron microscopy (SEM) is suitable for direct observation of TFC membrane structure, especially for superfine structure of ultrathin functional layer. The skin layer of TFC membrane is much denser than ultrafiltration membrane and its microstructure is more difficult to observe by SEM with regular way. At present, there are two common methods for fracturing membrane: brittle fracture of liquid nitrogen, embedded section. In addition, there are two less common methods with the help of precision instruments, like Focused Ion Beam cutting and Ion Milling technologies. We compare the advantages and disadvantages of four methods, and put forward a more convenient, practicable and effective method for SEM cross‐sectional analysis.
(1)Embedded Section: This method will be finished after embedding in epoxy resin, solidifying in thermostat and slicing by microtome. It has strict technical requirements for the operator. The cross section is damaged badly in the Fig.1.
(2)FIB cutting: We obtain the cross‐sectional sample using Carl Zeiss AURIGA Cross Beam FIB/SEM. FIB probe is Ga ion beam. The operating voltage and current is 30kV and 50pA respectively. The ion beam intensity is too high to keep the integrity of film structure. The cortex is damaged in the Fig.2. So this method is not suitable for soft materials.
(3)Ion milling: The process is completed by IM4000 of HITACHI. We select the section grinding mode to reduce the damage of structure, with the help of liquid nitrogen cooling mode. Although this method is somewhat better than FIB cutting, we still can't see the cortex distinctly.
(4)Brittle Fracture of Liquid Nitrogen: The cost of this method is very low. Although it's easy to use without the aid of other equipment, the SEM microstructure is difficult to observe directly and clearly. Fig.4a shows the low and high magnification images. We can see the film cross section is distorted and the cortex sagged.
The above methods have many limitations, because the toughness of membrane is too big to fracture easily. We have developed an improved sample frozen and fractured technology: the TFC membrane has swollen in ethanol at room temperature for several minutes, and then we put the sample in liquid nitrogen and fracture it with a certain slope. The functional cortex can be observed directly and effectively in the Fig.4b below.
In vivo visualizing the generation of hypochlorous acid using a novel selective fluorescent probe
Authors: Wang Haolu , Gravot Germain , Liang Xiaowen , Thorling Camilla , Zhang Run , Liu Xin , Roberts Michael 
Published: December 2016

Introduction

Hypochlorous acid (HOCl) is one of the most important reactive oxygen species, and plays a vital role in physiological events and diseases. Many fluorescent probes have been synthesized to detect HOCl. However, most of them were difficult to be distinguished from endogenous fluorophores in biological samples in vivo and can only be employed under one‐photon microscopy, often with drawbacks during further application. To enhance the sensing sensitivity and reduce photodamage, we developed a novel iridium(III) complex‐based fluorescent probe for
in vivo
visualizing the generation of HOCl at the cellular level.

Methods

A novel iridium(III) complex‐based Fc (ferrocene) dual‐signaling chemosensor (Ir‐Fc) was designed and synthesized as a highly sensitive and selective fluorescent probe for the
in vivo
recognition and detection of HOCl. The absorption and fluorescent properties were investigated under simulative physiological conditions. It is well documented that during hepatic ischemia‐reperfusion (I/R) injury, HOCl is generated by neutrophils and diffuses into hepatocytes, causing oxidant stress‐mediated injury. Therefore, we used a BALB/c mouse hepatic I/R injury model to test this probe. DermaInspect system (JenLab GmbH, Jena, Germany) was used for
in vivo
multiphoton microscopy (MPM) imaging of the liver after injection of 0.2 mL Ir‐Fc (50μM) from the portal vein. Systemic toxic effects were evaluated by examining the pathological changes of the major organs of mice.

Results
Figure 1A shows the reaction mechanism of the fluorescent response of Ir‐Fc toward HOCl. Ir‐Fc exhibited a strong positive fluorescent response only in the presence of HOCl, whereas negligible fluorescent signals were observed upon the additions of other reactive oxygen/nitrogen species and metal ions (Figure 1B). The dose‐dependent fluorescent enhancement followed a good linear relationship with HOCl concentration (Figure 2). In mouse liver with I/R injury, reduced autofluorescence was detected by MPM, indicating the hepatocyte necrosis (Figure 3D). As shown in Figure 3F, remarkable enhancement of the red fluorescence was observed in hepatocytes with decreased autofluorescence, indicating the reaction of Ir‐Fc with endogenous HOCl molecules. No obvious toxic effects were observed in histological examination of major organs after Ir‐Fc injection.

Conclusion

Ir‐Fc has good biocompatibility, low cytotoxicity, high specificity to HOCl, and rapid “off‐on” fluorescence. This complex is suitable as an
in vivo
HOCl detection probeat the cellular level.
Surface plasmon coupling revisited with electron energy loss spectroscopy
Authors: Das Pabitra , Martins Hugo Lourenço , Tizei Luiz , Kociak Mathieu 
Published: December 2016

In the last fifteen years or so, a significant amount of research activities took place in the field of metal nanoparticle plasmonics probed by fast electron beam. Local electron probe techniques like electron energy‐loss spectroscopy (EELS) and cathodoluminescence (CL) have advanced very fast during this time. Both these techniques helped us to gain considerable insight into the plasmonic properties of metallic nanostructures [1,2]. One of the many interesting nanostructures are the metal nanoparticle dimers. They can confine a huge amount of field in the gap. As the modes can be tuned precisely by changing the separation between the nanoparticles, they bear the promise to be used as sensors. It is well known that as the two individual particles approach each other, bonding and antibonding modes appear. Bonding and antibonding corresponds to in‐phase and out‐of‐phase interaction of the individual particle plasmons. Analogous to the molecular orbital theory, the bonding mode appears at lower energy and the antibonding mode at higher energy with respect to the individual particle plasmon mode [3]. With electron beam we can probe the precise location of the particle dimer to see which mode is excited at what location. Even though there is a wealth of literature on the plasmonic modes of individual metallic nanostructure, a systematic experimental study of coupled plasmons is deficient.
The central idea of the current work is to develop a deeper understanding on the coupling of the nanoparticle plasmons when they are brought close to each other (a few nanometers). For this purpose, we have chosen a cross shaped metal nanoparticle (Figure 1). We choose this structure for easy tuning of plasmon modes along the length of the rods by changing the rod length and because it is easy to model numerically. To have a detailed idea on the underlying physics, we start with the basic building block of the cross, i.e. a single nano rod. Then we increase the complexity of the structure by adding two rods perpendicularly to make a cross, and finally bringing two crosses close together to make a dimer. We make EELS on all of these structures and see the evolution of the modes. In this way, we will be able to explore the exact formation of different modes and the coupling between them.
To realize our idea, we have performed electron beam lithography to make silver nanostructures on Silicon Nitride substrate. EELS experiments are performed using a scanning transmission electron microscope (STEM) fitted with homemade EELS detection system [4]. To gain insight about the plasmonic modes, we perform 3D boundary element method (BEM) simulations [5] and compare with the experimental data. A representative EELS spectrum and the 2D plasmon maps has been shown in Figure 2.
In the conference, we will present and discuss our experimental and simulation results. This will provide new insight into the physics of plasmon coupling.
Inversion of dynamical scattering from large‐angle rocking‐beam electron diffraction patterns
Authors: Wang Feng , Pennington Robert , Koch Christoph 
Published: December 2016

A method for ab‐initio structure factor retrieval from large‐angle rocking‐beam electron diffraction (LARBED)[1] data of thin crystals is described and tested.
This method determines crystal structure factors and specimen thickness from the intensities of the diffraction spots alone, solving a nonlinear least‐squares problem. No additional information, such as atomicity or information about chemical composition, have been made use of.

In addition to a demonstration of the method on 120 keV experimental data of SrTiO
3
, where 456 structure factors have been retrieved, we analyze the dependence of the success of the reconstruction on specimen thickness and tilt range by applying this algorithm to simulated data. Our numerical experiments show that the dynamical inversion by gradient optimization works best if the beam tilt range is large and the specimen not too thick. At specimen thicknesses which allow for moderate multiple scattering, the large tilt amplitude effectively removes local minima in this global optimization problem, making ab‐initio structure factor retrieval possible.

In addition, a dynamic parallelism framework based on the Compute Unified Device Architecture (CUDA) is introduced, reducing the runtime of the optimization routine by two orders of magnitude when compared to running on a CPU.
The authors acknowledge funding by the Carl Zeiss Foundation as well as the German Research Foundation (Grant no. KO 2911/7‐1 and SFB 951).
Preparation of high fidelity holographic vortex masks using advanced
FIB
milling strategies
Authors: Schachinger Thomas , Steiger‐Thirsfeld Andreas , Löffler Stefan , Stöger‐Pollach Michael , Schneider Sebastian , Pohl Darius , Rellinghaus Bernd , Schattschneider Peter 
Published: December 2016

Holographic masks (HMs) with dislocation gratings placed in the condenser system of a TEM have been proven to be a reliable and robust method to impart quantized orbital angular momentum (OAM), as well as quantized magnetic moment onto the imaging electrons [1]. These so‐called electron vortex beams (EVBs) gathered a lot of attention due to some unusual properties like topological protection [2], peculiar rotation dynamics in magnetic fields [3] and intrinsic chirality. It has been suggested to use a holographic vortex mask as a vorticity filter after the specimen, in the selected area aperture holder, in order to detect spin polarized or other chiral transitions. This would bring up the unique chance to study magnetic properties of amorphous or nanocrystalline materials because the specimen's role as a crystal beam splitter – necessary in the standard energy‐loss magnetic chiral dichroism (EMCD) geometry ‐ is obsolete in this setup.
High fidelity HMs are needed for such experiments. Also, in order to achieve high vortex order separation, the grating periodicity should be very fine. To improve the signal‐to‐noise ratio of the EMCD measurements, the dimensions of the HMs need to be large. FIB milling proved to be a robust and reliable technique to produce HMs, but with ever‐increasing demands on structure size and fidelity, the ordinary milling strategy using raster‐ or serpentine scanning showed limited success. Therefore, we developed a new threefold milling strategy. The first step is to employ a so called “vector scan” technique, where “stream”‐files provide the possibility to fully control the position and dwell time of the ion beam to generate spiral milling paths for every hole in the HM structure (see Fig. 1). The next step is to reverse the milling order and ‐direction after each pass [4]. Inspired by [5], the last part consists of a position‐dependent dwell time reduction in the proximity of the hole edges to enhance the HM bar edge fidelity. Fig. 2 shows an exemplary 30 µm vortex mask with a grating periodicity of 500 nm and a thickness of roughly 700 nm.
One challenge encountered with this new strategy is limited digital‐to‐analog‐converter resolution as well as memory issues for large “stream”‐files. Using a state of the art FIB, it was possible to cut 50 µm HMs and to compare the ordinary raster scanning technique to the one proposed here, see Figs. 3 and 4. These results indicate that our new threefold scanning ansatz enhances the edge quality. Howerver, issues like sample‐ and beam drift as well as the crystallinity of the mask material have to be addressed in order to further improve the fidelity of the HMs' edges.
Investigating the loss spectrum of individual carbon nanotubes at high energy resolution in real and momentum space
Authors: Hage Fredrik S. , Ramasse Quentin M. 
Published: December 2016

Over the last quarter of a century Electron Energy Loss Spectroscopy (EELS) has proved itself as an excellent tool for investigating the plasmonic [1‐5] and electronic [1, 3, 4] response of carbon nanotubes: either by attaching a spectrometer to a Scanning Transmission Electron Microscope STEM [4, 5] or using a purpose built stand‐alone spectrometer [1‐3]. While STEM‐EELS provides superior spatial resolution to that of a stand‐alone spectrometer, it was not until recent improvements in electron source monochromation that the energy resolution of the two techniques became comparable. This was demonstrated by Sato and Terauchi [4] who used TEM –EELS to identify peaks in the loss spectrum of individual CNTs attributable to inter‐band transitions between van Hove singularities (vHs) in the CNTs' electronic density of states.
As an extension of the work of Sato and Terauchi [4], the present study is focused on the spatial and momentum dependence of the loss spectrum of individual CNTs. Fig. 1A shows loss spectra acquired from the single walled CNT in Fig. 1B using both a penetrating (1) and an aloof beam geometry (2), (3). The spectra in Fig. 1A are primarily characterised by peaks attributed to vHs (black arrows) [1, 3, 4], and, the π and π+σ plasmon resonances [1‐5]. The apparent red‐shift of the two plasmon peaks with increasing distance to the tube centre is consistent with literature [5]. Note the lack of a comparable red‐shift for the “vHs peaks” as well as a significant change in fine structure of the high energy shoulder of the π plasmon peak.

Resolving the CNT loss spectrum in momentum space allows for access to information not readily available in real space. Specifically, the momentum resolved spectra in Fig. 1C reveal that the vHs peaks are non‐dispersive (no peak shift with increasing momentum transfer), consistent with a reported measurement of a “bulk” sample of purified single wall CNTs [1]. Furthermore, it is shown that the “π peak” comprises two distinct plasmon modes: “π
1
“ and “π
2
”. The π
1
peak is non‐dispersive, thus indicating confinement perpendicular to the CNT axis, while the π
2
peak is dispersive, which in turn indicates significant plasmon propagation along the CNT axis [2, 3].
Analysis of
GaAs
compound semiconductors and the semiconductor laser diode using electron holography, Lorentz microscopy, electron diffraction microscopy and differential phase contrast
STEM
Authors: Sasaki Hirokazu , Otomo Shinya , Minato Ryuichiro , Yamamoto Kazuo , Hirayama Tsukasa , Yamasaki Jun , Shibata Naoya 
Published: December 2016

In order to develop and manufacture semiconductor devices which are key components of the optical telecommunication products, such as the semiconductor laser diode, it is essential to confirm whether it is manufactured as designed. Electric potential distributions of the semiconductor devices are designed in nanoscale, so two dimensional methods to evaluate the electrical potential in the semiconductors with a high spatial resolution are necessary for product management. The observation of the gallium arsenide (GaAs) model specimen was carried out by using the electron holography and Lorentz microscopy [1].
Lorentz images and intensity profiles are shown in FIG 1 (a)‐(f). The p‐n junctions are clearly seen in both the 0.6 mm under‐focused and over‐focused images, but hardly any interfaces of different dopant concentration can be observed in the images. FIG 2 shows the electron holographic reconstructed phase image. The p‐ and n‐type regions are clearly seen as areas of dark and bright contrast, and some differences in the changing dopant concentrations can also be seen.
A phase image of semiconductor laser diode by the electron holography is shown in FIG 3 [2]. In FIG 3(a), the interface region is approximately 5 μm. And the spacing between interface fringes is approximately 30 nm. Next, in order to observe the pn junction near the active layer in a high spatial resolution, the photograph was taken by changing the interference fringes conditions. The expanded phase image of a part of FIG 3(a), surrounded by a dotted line, is shown in FIG 3(b). Since the interference region is approximately 1.5 μm, and the interference fringe spacing is 5 nm, the spatial resolution is approximately 15 nm. As can be recognized from the phase image, we can understand that more detailed structure can be observed in the higher spatial resolution in comparison with the phase image in FIG 3(a). Here, the designed location of the pn junction was positioned at the dotted line, but it was found from the electron holography observation results that the pn junction did not exist in the original position. This semiconductor laser diode could not have the expected output characteristics. The structural defect of the pn junction, found out in this observation, is considered to be the cause.
For other semiconductor electric voltage evaluation methods by TEM, electron diffraction microscopy [3] which is one method of phase reconstruction method, differential phase contrast [4] (DPC) which is one method of STEM are also effective and possible to be utilized complementarily with the electron holography. We will discuss about these methods applied for semiconductor in this presentation.
3D
Elemental and interdependent reconstructions based on a novel compressed sensing algorithm in electron tomography
Authors: Printemps Tony , Bernier Nicolas , Robin Eric , Saghi Zineb , Hervé Lionel 
Published: December 2016

Electron Tomography (ET) is a key technique to perform 3D characterization at the nanometer scale [1]. 2D projections at different tilt angles are first acquired in an electron microscope, then an inversion algorithm is used to reconstruct the 3D volume of the sample from the dataset. Classically, ET is performed in a HAADF STEM mode in materials science leading to 3D Z‐contrast reconstructions. 3D elemental mapping based on EELS or EDS acquisitions is also possible in reconstruction theory [2]. Yet, reconstruction theory needs several hundreds of projections and 2D chemical mapping needs an important acquisition time and electron dose, therefore 3D elemental mapping is challenging. Nowadays, microscopes improvements limit the acquisition time of 2D chemical mapping. Moreover, powerful state‐of‐the‐art reconstruction algorithms make possible the reconstruction from a limited dataset of a few dozens of projections only. As a consequence 3D elemental mapping is now possible with a reasonable acquisition time of a day or less.
New reconstruction algorithms add prior knowledge on the object to compensate for the lack of information due to limited number of available projections. The prior knowledge can be a limited number of possible grey levels in the reconstruction to perform discrete tomography [3]. This correspond to a limited number of known materials in the sample. In the case of Compressed Sensing (CS) algorithms [4], the prior knowledge is a sparsity of the object expressed in a particular basis. A special case of CS reconstruction is the use of the gradient sparsity of the object to perform Total Variation Minimization (TVM) algorithms [5]. In that case, objects constant by parts are preferably reconstructed.
We propose a mixed approach suited for EDS acquisition. That mixed approach combines both projection denoising [6] and a TVM based algorithm that uses the reconstructions of each element all together. This new approach leads to higher reconstruction accuracy since a new kind of prior knowledge is used. Indeed, reconstructions of different elements should not be independent since a variation of an element is most of the time correlated to a variation of at least another element. The algorithm will be introduced. Simulations using projections with high Poisson noise and strong misalignment will be used to show the accuracy of our approach. Experimental results for a GaN‐TiAl intermetallic sample in EDS tomography will also be presented.
This work was supported by the French “Recherche Technologie de Base” (RTB) program. The authors acknowledge access to the nanocharacterization platform (PFNC) at the Minatec Campus in Grenoble. The authors thank Alphonse Torres from CEA Leti for providing the intermetallic specimen.