bluuebunny/crossref_metadata_2025_split huggingface dataset:
In‐situ electrical measurements of Graphene Nanoribbons fabricated through Scanning Transmission Electron Microscopy
Authors: Vicarelli Leonardo , Heerema Stephanie J. , Dekker Cees , Zandbergen Henny 
Published: December 2016

We recently demonstrated a controllable and reproducible method to obtain suspended monolayer graphene nanoribbons with atomically defined edge shape [1]. Our method exploits the electron‐beam of a Scanning Transmission Electron Microscope (accelerated at 300 kV) to create vacancies in the lattice by knock‐on damage and pattern graphene in any designed shape. The small beam spot size (0.1 nm) enables close‐to‐atomic cutting precision, while heating graphene at 900 K during the patterning process avoids formation of beam‐induced Carbon deposition and allows self‐repair of the graphene lattice. Self‐repair mechanism is essential to obtain well‐defined (zig‐zag or armchair) edge shape and, if the electron beam dose is lowered, to perform non‐destructive imaging of the graphene nanoribbons.
Drawing the electron‐beam path with a software script, we were able to obtain reproducible graphene nanoribbons with sub 10 nm width. Using an in‐house built microscopy holder equipped with electrical feedthroughs, we performed 2 and 4 wire measurements on several graphene nanoribbons, with different number of layers. Wide nanoribbons (width> 50 nm) exhibited ohmic behaviour, with conductivity linearly proportional to the width. Narrower ribbons (10 nm < width < 50 nm) displayed non‐linear current‐voltage (IV) relationship at low temperature (4 K, ex‐situ), possibly indicating the opening of a band gap. The narrowest ribbon was 1.5 nm wide, with strong non‐linear IV also at room temperature.
Electrical measurements were also performed in the high temperature range (300 K – 900 K), from which we concluded that thermal generated carriers give the main contribution to electrical conductivity above room temperature.
Electron tomography with sub‐5‐second temporal resolution for dynamic in situ transmission electron microscopy
Authors: Migunov Vadim , Leary Rowan K. , de la Mata María , Russo‐Averchi Eleonora , Tütüncüoglu Gözde , Morral Anna Fontcuberta i , Arbiol Jordi , Dunin‐Borkowski Rafal E. 
Published: December 2016

Electron tomography (ET) is an important technique for the study of the three dimensional morphology, structure and chemical composition of nanoscale materials in the transmission electron microscope (TEM). Although ET is potentially a powerful tool for
in situ
three‐dimensional TEM studies of catalytic reactions, growth processes, phase transformations, switching mechanisms and defect nucleation, motion and interactions, its application to dynamic experiments has been limited, since typical acquisition times for tilt series are typically tens of minutes or longer [1].

We have recently demonstrated the rapid acquisition of a tomographic tilt series comprising approximately 3500 images between +30° and −70° in only 3.5 s, as shown in Fig. 1) [2]. Here, we apply the technique to the three‐dimensional imaging of the thermal segregation of an InAs V‐shaped nanomembrane [3]. The membrane was heated
in situ
in an FEI Titan TEM up to a temperature of 420 °C. Changes in membrane morphology were tracked by acquiring images on a Gatan K2‐IS camera at 400 frames per second while continuously tilting the specimen between +60° and −65°. Each tilt series (i.e., one rotation in one direction) was acquired in approximately 4.3 s and comprised ~1700 frames. Selected frames are shown in Figs 2 and 3.

The reconstruction of time‐dependent (four‐dimensional) tilt series can be performed using two approaches: i) Reconstruction of each individual tilt series and interpolation between each reconstruction in the time domain, resulting in a time resolution that is limited by the acquisition time for each tilt series (i.e., 4.3 s); ii) Model‐based reconstruction, involving tracking of changes between individual frames within each tilt series, resulting in sub‐second temporal resolution. We are presently pursuing both approaches.
We are grateful to Cory Czarnik and Ana Pakzad from Gatan Inc. for making the K2 IS camera available for the experiments and to the European Research Council for an Advanced Grant.
Visualization of aligned collagen fibrils in cartilage by second harmonic generation microscopy
Authors: Finnøy Andreas , Olstad Kristin , Lilledahl Magnus 
Published: December 2016

Articular cartilage is located at the bone ends in synovial joints and enables smooth and pain‐free joint motion. Its function is in large part determined by a network of collagen fibrils organized into zones and compartments, but little is known about how this organization is achieved in growing animals [1]. The articular cartilage develops superficially to a layer of temporary growth cartilage. The growth cartilage is responsible for the expansion of the bone ends and is replaced by bone during growth. The interface between the immature articular cartilage and the growth cartilage is histologically indistinguishable [2]. On the other hand, aligned collagen fibrils encapsulate cells in the articular cartilage but not in the growth cartilage, so the immature articular cartilage and the growth cartilage can be distinguished by locating these fibrils with transmission electron microscopy (TEM) in growing animals [1]. However, TEM requires extensive sample preparation and has limited field of view.
Second harmonic generation (SHG) microscopy is a promising image modality that is highly specific to collagen fibrils without any staining [3]. SHG is a coherent nonlinear optical process that is specific for non‐centrosymmetric structures such as collagen fibrils and is characterized by frequency‐doubling of light. In contrast to fluorescence, the SHG intensity and radiation direction is highly sensitive to the arrangement of collagen fibrils. In addition, as the arrangement of fibrils can vary at different length scales, this sensitiveness can depend on the size of the focal volume.
The aim of this study was to examine if the aligned fibrils encapsulating cells could be visualized by SHG microscopy without any staining in order to locate the immature articular cartilage of a growing animal.
The cartilage located at the distal femur of growing piglets was imaged by detecting the forward and backward directed SHG. Focusing objectives with different numerical aperture (NA), i.e. focal volume, were used to examine the collagen fibrils at different length scales. The results demonstrated that the ratio of forward to backward SHG was dependent on the NA and that the dependence on the NA varied with distance from the articular surface (Figure 1). The high forward to backward ratio at low NA near the articular surface (Figure 2) was interpreted to represent the aligned fibrils characterizing the articular cartilage. The gradual transition between the immature articular cartilage and the growth cartilage was therefore clearly visualized by SHG, and SHG microscopy is therefore a promising technique to study the development of the collagen matrix in articular cartilage.
Decontamination capacity of a fish after trophic contamination with gold nanoparticules: ultrastructural study
Authors: Mesmer‐Dudons Nathalie , Chongaud Aurore , Mornet Stephane , Feurtet‐Mazel Agnès , Maury‐Brachet Régine , Baudrimont Magalie 
Published: December 2016

Nanomaterials represent today a major economic and technological issue, because of their innovating properties rising from their nanometric size (1 to 100 nm) and in particular of their chemical compositions, sizes, specific surfaces and varied surface qualities. These nanomaterials are present in sectors as varied as building, car industry, chemistry, energy or health, and therefore can be found in natural ecosystems without knowing yet their potential impacts.

In this context, trophic transfer of gold nanoparticles (AuNPs) between periphytic biofilms and a periphytophage fish
Hypostomus plecostomus
as final consumer has been studied in laboratory. Histological analyses have been performed at the two trophic levels with a particular focus on transmission electronic microscopy (TEM) observations in fishes.

In upstream running waters, periphytic biofilms are constituted by the association of micro‐organisms secreting an organic polymermatrix. Diatoms (brown microalgae) as a major component of these biofilms ensure a great part of the primary productionin the upstream running watersand are at the basis of their food web.

A contamination of these microorganisms by AuNPs could be vector of a trophic transfer of these nanomaterials along the trophic chain. Thus we determined if a trophic transfer of AuNPs was possible between natural periphytic biofilms and the fish
Hypostomus plecostomus
.
H. Plecostomus
is a tropical benthic fish with a ventral mouth modified into suction cup and adapted to graze the periphytic biofilms.

Analyses of gold bio‐accumulation in fishes were performed after 7 days of contamination, followed by a period of depuration of 14 days. These analyses were supplemented by an observation of AuNPs localization in tissues and cells by TEM and the toxic effects of AuNPs were also observed in them.
The results showed a trophic transfer of AuNPs between biofilms and fish, with a significant gold bioaccumulation in several organs (heart, spleen, liver, muscles). TEM observations revealed also a concentration of AuNPs in the spleen of the fish, localized especially in the erythrocytes and an important destructuration of the muscle fibers. After depuration, AuNPs totally disappeared from the erythrocytes, but were concentrated in the melanomacrophages, along with a recuperation of the muscles fibers, suggesting an important capacity of this fish to detoxify this type of nanoparticles.
Soft
X
‐Ray cryo‐tomography reveals ultrastructural alterations of the host cell during Hepatitis
C
infection
Authors: Perez‐Berna Ana Joaquina , Rodríguez Maria Jose , Sorrentino Andrea , Chichon Francisco Javier , Friesland Martina , Carrascosa Jose Lopez , Gastaminza P , Pereiro Eva 
Published: December 2016

Chronic hepatitis C virus (HCV) infection causes severe liver disease in millions of humans worldwide. Pathogenesis of HCV infection is strongly driven by a deficient immune response of the host, although intersection of different aspects of the virus life cycle with cellular homeostasis is emerging as an important player in the pathogenesis and progression of the disease.
Cryo soft X‐ray tomography (cryo‐SXT) was performed to investigate the ultrastructural alterations induced by the interference of hepatitis C virus (HCV) replication with cellular homeostasis. Native, whole cell, three‐dimensional maps were obtained in HCV replicon‐harboring cells and in a surrogate model of HCV infection at 40nm resolution. Tomograms from HCV‐replicating cells show blind‐ended endoplasmic reticulum (ER) tubules with pseudo spherical extrusions and marked alterations of mitochondrial morphology that correlated topologically with the presence of ER alterations, suggesting a short‐range influence of the viral machinery on mitochondrial homeostasis.
Both mitochondrial and ER alterations could be reverted by a combination of sofosbuvir/daclatasvir, which are clinically approved direct‐acting antivirals (DAAs) for the treatment of chronic HCV infection. In addition to providing structural insight into cellular aspects of HCV pathogenesis our study illustrates how cryo‐SXT is a powerful three‐dimensional wide‐field imaging tool for the assessment and understanding of complex cellular processes in a setting of near native whole hydrated cells. Our results also constitute a proof of concept for the use of cryo‐SXT as a platform that enables determining the potential impact of candidate compounds on the ultrastructure of the cell that may assist drug development at a preclinical level.
Generation of super‐oscillatory electron beams beyond the diffraction limit
Authors: Remez Roei , Tsur Yuval , Lu Peng‐Han , Tavabi Amir H. , Dunin‐Borkowski Rafal E. , Arie Ady 
Published: December 2016

In 1873, Ernst Abbe discovered that the imaging resolution of conventional lenses is fundamentally
limited by diffraction
, which, since then, has been overcome using a variety of different approaches in optical microscopy. In electron microscopy, thanks to remarkable developments in aberration corrected electron optics, the resolution of transmission electron microscopes (TEMs) and scanning TEMs (STEMs) has reached the sub‐Ångström regime. However, it is still limited by instrumental stability, residual higher‐order aberrations and the
diffraction limit
of the electron‐optical system. Recently, a concept termed super‐oscillation, which is analogous to the idea of super‐directive antennas in the microwave community [1], was proposed [2, 3] and applied in light optics for far field imaging of sub‐wavelength, barely‐resolved objects beyond the diffraction limit [4]. A super‐oscillating function is a band‐limited function that is able to oscillate faster locally than its highest Fourier component and thereby produce an arbitrarily small spot in the far field.

Here, we demonstrate experimentally for the first time a super‐oscillatory electron beam whose characteristic probe size is much smaller than the Abbe diffraction limit. Figure 1(a) shows scanning electron microscopy (SEM) images of a conventional grating mask (left) and a super‐oscillation off‐axis hologram (right) that have the same outer diameters (10 µm). The masks were fabricated by focused ion beam milling 200‐nm‐thick SiN membranes coated with 150 nm Au. The masks were inserted into the C2 aperture plane of a probe‐corrected FEI Titan 80‐300 (S)TEM. Owing to the probe aberration corrector and relatively small numerical aperture (convergence semi‐angle), diffraction‐limited spots could be easily obtained from the conventional grating (Fig. 1, left), while a super‐oscillatory electron probe, which was generated at the first diffraction order (Fig. 1, right), produced a much smaller hot‐spot in the center. The size of the super oscillation hot‐spot is approximately one third of that of the diffraction‐limited spot. It could theoretically be decreased further, even below the de‐Broglie wavelength of the electrons, by varying the ratio between the inner and outer radii.
Further applications of such super‐oscillatory electron wave functions, e.g. enhanced STEM imaging, will be presented.
Investigation of Plasmonic Modes of Gold Tapers by
EELS
Authors: Guo Surong , Talebi Nahid , Sigle Wilfried , Vogelgesang Ralf , Esmann Martin , Becker Simon F. , Lienau Christoph , van Aken Peter 
Published: December 2016

Plasmonic tapers have been studied intensively due to the ability of adiabatically coupling the propagating surface plasmon polaritons along their shaft to the nanolocalized plasmons at their apex. Therefore, they can find applications in the fields of sub‐diffraction‐limit nanofocusing, ultrafast photoemission, and near‐field optical microscopy.
We investigate the plasmonic modes of three‐dimensional single crystalline gold tapers by means of EELS (electron energy loss spectroscopy) and FDTD (finite‐difference time‐domain) numerical calculation. We observe a broadband excitation in the proximity of the apex and discrete higher‐order azimuthal plasmonic modes along the taper shaft in the gold taper with an opening angle of ~45°. Interestingly, the energy dispersions of these higher‐order plasmonic modes are roughly proportional to the inverse local radius. The importance of phase‐matching between electron field and radiative taper modes in mesoscopic structure is demonstrated [1]. The role of an alternative mechanism suggested by Schröder et al. [2] was analyzed by systematically studying changes in the dispersion of higher‐order plasmonic modes of gold tapers for different opening angles.
Developing new electron interferometry configurations in
I2TEM
thanks to electron optics simulations
Authors: Kubo Yudai , Gatel Christophe , Taniguchi Yoshifumi , Snoeck Etienne , Houdellier Florent 
Published: December 2016

The
In situ
Interferometry Transmission Electron Microscope (I2TEM), is a microscope designed to easily performed new electron interferometry experiment [1,2,3]. The microscope is equipped with a 300kV cold field emission source, one electrostatic Möllenstedt biprism (BP) installed before the three condenser lenses, two goniometer stages situated respectively above and inside the objective lens pole piece (namely high resolution stage and Lorentz stage) and finally three BPs placed between the intermediate lenses. The strength of this microscope lies in its wide optical flexibility, which can be used to develop new configurations very difficult to obtain using standard TEM. On the other hand, this flexibility increases the optical complexity of the operation and implies being able to simulate the electrons trajectories as a function of the various optical conditions (lenses excitations, High voltage, gun lens ratio, …) to predict “a priori” the hologram properties which will be obtained (width, interference fringes, …).

To perform such simulations, all lenses strengths have been calculated using finite element modelling software COMSOL multiphysics (see figure 1) [4], as a function of their ampere‐turns excitations. These results are then used in SIMION software (see figure 2) [5] to compute the complete electron trajectories starting from the FE tip through the biprism to finish in the detector plane.
The simulations are finally compared to experimental data in order to calibrate the model.
Excitonic Properties of Inorganic‐Organic Hybrid Perovskites and Nanophotonic Devices
Authors: Xiong Qihua 
Published: December 2016

Excitonic Properties of Inorganic‐Organic Hybrid Perovskites and Nanophotonic Devices

Qihua Xiong
School of Physical and Mathematic Sciences & School of Electrical and Electronic Engineering
Nanyang Technological University, Singapore, 637371

Abstract:
In this talk, we present investigations of vapor phase synthesis of purely inorganic or organic‐inorganic perovskites nanoplatelets by a van der Waals epitaxy mechanism and their excitonic properties. Those crystals exhibit 2D well‐faceted triangular, hexagonal or square geometry with thickness range of tens to hundreds of nanometers. Optical spectroscopy investigations suggest that the crystals have large exciton binding energy, high external quantum efficiency and long diffusion lengths. The naturally formed high‐quality planar whispering‐gallery mode cavities ensure adequate gain and efficient optical feedback for low‐threshold optically pumped in‐plane nanolasers ranging from ultraviolet and near‐infrared, with an exceptionally high quality factor (>4000) in purely inorganic perovskite square‐shaped crystals. Our findings open up a new class of wavelength tunable nanomaterials potentially suitable for on‐chip integration and flexible optoelectronic devices. Progress in light‐emitting diode and laser cooling will also be discussed.
Analysis of Food Packaging Layered Polymers by
SEM/EDS
and Raman
Authors: Konopka John , Thompson Keith 
Published: December 2016

Food packaging can consist of many layers of materials each engineered for different purposes. The layers may be very thin, in some cases much less than one micron. Principally composed of polymers layers may be composed of inorganics and inorganic particles may be embedded by design or as artifacts. Analysis for quality assurance or failure analysis is difficult due to the complex nature of the sample.
Raman can easily identify the polymers used in these products. Raman mapping has a resolution of one micron or better. SEM imaging easily achieves a resolution of ten nanometers and can distinguish different polymers by their appearance in electron imaging. EDS achieves a spatial resolution of a few tens of nanometers. It can identify all elements present here except hydrogen.
Together these techniques provide complementary information. In addition imaging and elemental mapping with SEM/EDS may be faster than Raman mapping.
For this work a JEOL JSM‐7610F FESEM equipped with a Thermo Scientific NS7 EDS analyzer and 60mm2 area Ultradry silicon drift detector were used for the SEM/EDS data. A Thermo Scientific DXRxi Raman spectrometer with optical microscope was used for the Raman spectroscopy.
The SEM conditions were 10 kV acceleration voltage and about 3 nA beam current.
The sample used here is a cross section of a commercially available potato chips bag. The sample was sectioned by a fresh razor blade. For SEM/EDS the sample was carbon coated.
Figure 1 compares the results from both SEM/EDS and Raman. In this view the interior of the package is towards the top of the image. The right image shows a Backscatter Electron (BSE) image of the cross
section overlaid by elemental maps for Al, Ti, Si and O. Twelve layers were identified by inspection ranging from about 25 microns to approximately 175 nm thick. Some are not visible at this low magnification view. An Al layer about 200 nm thick was seen. A 175 nm thick layer containing S and Cl was found (not shown in the figure). Several layers contained Ti rich particles. Some particles of silicon oxide, possibly artifacts, were seen. The live time for this map was 931 seconds.
The image at left in Figure 1 shows the results of the Raman mapping analysis. The identified polymers layers and their thicknesses are labeled. In general the two techniques agree well on the overall composition of the sample. The Raman analysis identifies the polymers making up each of the layers which was not possible by SEM/EDS. It also found the inorganic rutile particles embedded in some of the layers. It did not find any of the sub 200 nm layers seen in the SEM.