bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enamel evolution: Back in time by a molecular manipulation
Authors: Wald Tomas , Spoutil Frantisek , Osickova Adriana , Prochazkova Michaela , Benada Oldrich , Kasparek Petr , Bumba Ladislav , Klein Ophir , Sedlacek Radislav , Sebo Peter , Prochazka Jan , Osicka Radim 
Published: December 2016

Biomineralization is one of the key processes during vertebrate evolution that incorporates calcium and phosphate ions into soft matrices in the form of hydroxyapatite. Occurrence of mineralized tissues have offered the basis for various adaptive phenotypes such as endoskeleton for locomotion (bone), body armor for protection and teeth (enamel, dentin) for predation. Enamel is unique among the mineralized tissues, as it is formed on specific network of enamel matrix proteins (EMPs) secreted by epithelial ameloblasts. The two key structural proteins of enamel, amelogenin (AMEL) and ameloblastin (AMBN), self‐assemble into higher‐ordered structures from monomeric intrinsically disordered subunits as does the type I collagen (COL1), the predominant matrix protein in bone and dentine. While COL1 undergoes self‐assembly via consecutive Gly‐X‐Y motif, the mechanism of self‐assembly of EMPs and their subsequent role in formation of organized layer of hydroxyapatite crystals remains poorly understood.
We report here a novel evolutionary conserved self‐assembly motif common to the key structural enamel matrix proteins AMBN and AMEL. The presence of this motif is essential for self‐assembly of AMBN and AMEL into higher‐ordered structures. These structures are essential for proper enamel formation. Transgenic mice that were unable to produce supramolecular structures of AMBN due to point substitutions within the identified self‐assembly motif then produced severely affected enamel with simplified organization. Despite the normal cellular organization, EMPs secretion and Ca and P levels within the growing enamel of transgenic mouse, the affected enamel lacked organized prismatic structures and showed only radial organization without visible Hunter‐Schreger bands. Moreover, enamel of mutant mice contained an enormous portion of interprismatic matrix with hypomineralized, yet well recognizable, crystallites, while no formation of oriented crystallites was observed within the compromised prisms.

This is the first
in vivo
evidence that the formation of supramolecular structures of enamel matrix proteins was essential for evolution of highly structured enamel in mammals.
Tailoring the wave function of electron probes for the selective detection of plasmonic modes
Authors: Guzzinati Giulio , Lourenço‐Martins Hugo , Béché Armand , Kociak Mathieu , Martin Jerôme , Verbeeck Jo 
Published: December 2016

Electronic spectroscopies are important in the study of localised surface plasmon resonances of metallic nanostructures, allowing to detect and image the strong spatial variations in the electrical field of the induced resonances of a single nanoparticle [1].
These techniques do however present some drawback when compared to their optical counterparts. While optical spectroscopies can make use of polarisation to directionally probe the response of a nanoparticle, an electronic beam can't discriminate between energy‐degenerate eigenmodes and is also blind to optical activity and dichroism.
Here we present a way to expand the applicability of EELS to the characterisation of plasmonic resonances by exploiting the recently developed methods of electron beam shaping through phase manipulation [3].
This radically new approach is based on the idea of tailoring the electronic probe to fit the properties under investigation that can then be selectively detected, allowing to perform new measurements that were previously impossible [3].
In particular, we first show how the phase in the electron beam's complex wave function couples to the electric potential of the plasmonic excitation (see fig1), allowing to selectively detect localised plasmonic excitations that possess the same symmetry as the electron probe [4].
While this concept is entirely general and potentially applicable to any plasmonic resonance, we decide to focus a first experimental demonstration on detecting the dipolar mode of a nanorod.
The ideal probe for this purpose is formed by two intensity lobes opposite in phase as shown in figure 1a, which we successfully generate in the TEM by applying state of the art phase manipulation techniques.
Finally, we show experimental proof of the method's effectiveness on purposefully made test sample, demonstrating the viability of this new approach and opening to a new generation of plasmon oriented TEM experiments, that will expand in parallel with the availability of wave manipulation methods.
Generation of nondiffracting beams: beam shaping beyond holographic reconstruction
Authors: Guzzinati Giulio , Béché Armand , Verbeeck Jo 
Published: December 2016

The last few years have seen a rapid acceleration in the field of beam manipulation [5].
Central to this expansion is the idea that the purposeful design of the beam's wavefunction can imbue the electron with new properties that potentially enable new measurements previously impossible.
Examples of this are the orbital angular momentum possessed by electron vortex beams [1], or the reduced diffraction of Airy and Bessel beams [2–4].
In these studies, holographic reconstruction remains the most widely used method to generate new wave types due to its generality and flexibility but presents several shortcomings, chiefly the production of multiple diffracted beams [1–3,5].
Here we showcase different approaches to the production of reduced diffraction beams.
We generate Airy waves by a careful tuning of the aberration function of an aberration corrected TEM, and produce a Bessel beam by limiting the angular spread of the electrons with an annular aperture.
We study the beam propagation to prove the limited diffraction, and give experimental proof of extended depth of focus in imaging with Bessel beams.
Surface‐sensitive investigation of semiconductor devices with a signal‐selective SEM detection system
Authors: Jiruše Jaroslav , Kološová Jolana , Mareš Petr , Váňa Rostislav 
Published: December 2016

The detection system of a scanning electron microscope (SEM) is just as important for image quality as the design of its electron optics [1]. Recent studies [2, 3] emphasize the importance of angle‐ and energy‐filtering of backscattered electrons signal (BSE) to reveal details not usually observable in the integral BSE signal.
Here we introduce a novel detection system tested on a recently developed ultra‐high resolution electron optical column [4, 5] that comprises three BSE detectors capable of angle‐ and energy‐filtering. The system can be switched between a “high‐signal” mode where no bias is applied to the filtering grid and an “energy‐selective” mode where the filtering voltage can be tuned to achieve various degrees of signal separation.
High‐pass energy filtering enables detection of BSEs which have undergone minimal energy loss. Their escape depth is limited and the resulting micrograph becomes surface sensitive. This is beneficial for samples with complex surface and sub‐surface structure. Clear visualization of the topmost layer of the sample is critical e.g. for failure analysis of 3D semiconductor devices, given the continuously decreasing dimensions of the local structures in such devices.
Figure 1 shows a SEM micrograph of a semiconductor memory device cross‐section acquired at 3 keV primary beam energy and 265 pA probe current. Contrast of the images decreases continuously with increasing bias of the filtering grid. With no bias applied the material contrast is highest, yet it contains information about both surface and subsurface area of the specimen. With increasing filtering bias only the electrons backscattered from the very surface of the sample are detected. This is in agreement with theoretical simulations for 3 keV primary beam in silicon that show an escape depth of 80 nm for the integral BSE signal and only 2 nm for the low‐loss BSE signal.
Atomic structure and segregation phenomena at copper grain boundaries
Authors: Meiners Thorsten , Liebscher Christian H. , Dehm Gerhard 
Published: December 2016

Abstract

The segregation of impurity atoms to grain boundaries can have significant influence on the cohesive properties, atomic arrangements and the mechanical properties of such interfaces. Therefore, it strongly impacts the macroscopic behavior of materials and understanding the atomic structure and related segregation behavior at grain boundaries is crucial to tailor materials with optimized physical properties
[1]
. Copper (Cu) is an attractive material for electronic applications, because of its good electrical and thermal conductivity. The effect of Sulphur on grain boundaries in Cu is of particular interest since it is improving the electromigration resistance but can also lead to grain boundary embrittlement
[2]
.

In this study the atomic structure and chemistry of grain boundaries in polycrystalline Cu with variable Sulphur content (7 – 4000 ppm) are analyzed. In order to determine the distribution, size and orientation of the grains, Electron Backscatter Diffraction (EBSD) measurements were performed, as shown in Figure 1. The measurement reveals a grain size of 1‐4 mm and an orientation of the grain normal close to the [001] direction. Transmission electron microscopy (TEM) specimens are prepared conventionally by grinding, electro polishing and Ar
+
ion beam milling at specific regions from the EBSD scan in order to select special grain boundaries. This is shown exemplarily by the black circle in Figure 1.

TEM methods (bright‐field imaging, selected area diffraction and high resolution TEM) are used to investigate the structure of selected grain boundaries. A preliminary example represented in Figure 2 reveals a high angle grain boundary. The specimen is tilted so that the upper grain is oriented in [001] zone axis while the resulting orientation of the lower grain is close to the [013] zone axis. The tilt component between both grains was determined to by measuring the misorientation between the (200) reflexes of both grains which is in good agreement with the EBSD measurement. The twist component of this random grain boundary is not yet fully determined and is part of current investigations.
The atomic structure and segregation of Sulphur are characterized by aberration‐corrected scanning transmission electron microscopy (STEM) in combination with analytical techniques including energy‐dispersive X‐ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). Hence, information on the atomic arrangement of impurity atoms (interstitial and substitutional), the respective bonding and possible grain boundary precipitates will be obtained with sub‐nanometer resolution.
Reflection profile and angular resolution with Precession Electron Diffraction
Authors: Rauch Edgar , Renou Gilles , Veron Muriel 
Published: December 2016

Template matching has proved to be an efficient numerical approach to identify orientation and/or phase signatures in electron diffraction patterns [1]. With this technic, all patterns for all orientations and all phases considered are pre‐calculated and compared to the experimental data by cross‐correlation. The capacity of the approach to recognize the diffracting signal is substantially improved with precession electron diffraction (PED). This is because dynamic effects are partly swept out of the experimental signal. Of interest is the fact that, up to now, templates were always computed without including precession. In particular the specific reflection profile resulting from the beam rotation was never considered properly. The present work is an attempt to enhance the degree of matching by adapting the templates to precession in particular for large precession angles.

First, the Bragg spot profile is determined for Si single crystal by tilting progressively the sample. The pattern collection procedure is similar to the fast diffraction tomography setup of Gemmi et
al
[2]. The precession angle was monitored with the Nanomegas Digistar P1000 attachment to a JEOL 2100F TEM and set up to 0.3, 0.6 and 1.2°. The crystal orientation evolution is followed with the ASTAR system through template matching and compared to the quasi linear trend expected from the constant angular speed of 1°/min imposed by the TEM goniometer.

The change in reflection profile with increasing precession angle is illustrated in figure 1. The profile exhibits two maximums separated by twice the precession angle. This shape, systematically recorded, is modeled and introduced in the template generation routine. The improvement in angular resolution is characterized by comparing the misorientation measurements with respect to the expected linear trend (Fig 2).
The templates computed with the recorded PED profile, differ significantly from the standard ones (Fig 3). The resulting set of templates being closer to the diffraction patterns acquired with precession, the crystal orientation is determined with an increased accuracy (Fig. 2.b), at least at large precession angles. The standard deviation obtained without and with precession adaptation is nearly identical and equal to 0.17° for precession angles lower or equal to 0.6°. By contrast, this value degrades down to 0.5° at the largest precession angle if no precession correction are included (Fig. 2) but remains equal to 0.17° with adapted templates.
Besides, the orientation resolution may be further refined by using the interpolating algorithm presented elsewhere [3]. With adapted templates and interpolation the standard deviation decreases down to 0.13°, for the largest precession angle. A non‐intuitive conclusion of the present work is that the angular resolution of the orientation determination is not bounded by the precession angle.
Mapping electrostatic potentials and deformation in semiconductor devices by off‐axis electron holography and other techniques
Authors: Boureau Victor , Cooper David , Bernier Nicolas , Rouviere Jean‐Luc 
Published: December 2016

Off‐axis electron holography can be used to measure the electrostatic and magnetic potentials in semiconductor devices with high‐sensitivity and nm‐scale resolution [1]. In this presentation we will show experimental results that have been obtained using combinations of electron holography, precession diffraction and differential phase contrast (DPC) on a range of different semiconductor devices.
Deformation maps have been acquired using dark field electron holography on a variety of different device structures and these results have been compared to those obtained by precession electron diffraction (NPED). Figure 1 shows STEM images and results obtained by dark holography and NPED on a Si specimen containing 10‐nm‐thick SiGe layers with different Ge concentrations and also a recessed source and drain SiGe device. The deformation maps obtained by dark holography and shown here have a spatial resolution of 6 nm and a precision of 0.05 %. The maps obtained by precession electron diffraction have a spatial resolution of 2 nm and a precision of 0.02 %. In this presentation we will show the advantages and difficulties associated with the use of the different techniques [2].
We will also compare electron holography and DPC for dopant profiling on fully processed and electrically tested devices. Figure 2(a) and (b) shows STEM images that have been acquired from two different pMOS devices with different spacer widths. The spacers are used to prevent dopants from diffusing under the gate during the activation anneals. Figure 2(c) shows how the specimen is rotated to remove the top metal layers in the device, backside milling is then used to provide a high quality TEM specimen. Figures 2(d) and (e) show maps of the electrostatic potential in the devices that have been acquired using off‐axis electron holography. The spatial resolution in these maps is 5 nm and the difference in the potential distribution under the gate can be clearly seen. Potential profiles have been obtained from across the device and the parameters such as the electrical gate width can be measured. From the analysis of these real devices, the advantages and problems that are associated with electron holography and DPC can be discussed.
Great advantages of using low voltage
HR‐SEM
in spatial resolution and sensitivity for low energy
X
‐ray analyses
Authors: Shunsuke Asahina , Hideyuki Takahashi , Masaru Takakura , Schüth Ferdi , Osamu Terasaki 
Published: December 2016

Understanding surface fine features, such as topological and compositional information, is essential for controlling synthesis conditions of these materials and for designing novel materials and utilizing their functions. The materials are becoming complicated composites composed of Nano crystals in order to have functions with better performance. Therefore, higher spatial resolution, sensitivity and capability are required for characterization techniques are required now. The recent developments in compound type objective lens, electron beam deceleration method, high solid angle multi EDS system and Soft X‐ray Emission Spectrometry (SXES) of high‐resolution scanning electron microscopy (HR‐SEM) show great advances for the study of structures, chemical information, and electron state of Nano structured materials (1). Here, we will discuss newly developed spectroscopy approaches in EDS and SXES, and show some of their examples using low voltage (LV) HR‐SEM.

The electron beam deceleration method brings a lot benefits. Because it is improving size of electron beam diameter due to smaller aberration even at LV condition, high probe current condition and long working distance (2). Fig. 1 shows high spatial resolution EDS map from Au@TiO
2
Yolk‐shell type sample where a gold nanoparticle with 15 nm in diameter is encapsulated in a TiO
2
hollow sphere. The gold nanoparticles are well resolved within 3 min even at low electron landing‐energy (see observation conditions in the Fig caption).

The low energy SXES spectra obtained from Al‐B nano composites are shown in Fig. 2. SXES technique requires high probe current to acquire enough X‐ray signals as it is based on wavelength dispersive spectrometry (WDS). The spectra from small area of aluminum alloy (a) and aluminum boride (b) show different peak top energy and shape for aluminum L‐line at around 70 eV. In addition, the boron peak was also detected at around 67 eV. The spectra at this energy range, which corresponds to K‐line from light elements including Lithium, was hard to observe by EDS and WDS before. So the SXES detector has high‐energy resolution and can also detect extremely low energy X‐ray.
The electron beam deceleration method has advantages in SXES analysis. We demonstrated SXES line profiles in between metal Aluminum and Aluminum boride in Fig. 3. Actually, there is deference between with beam deceleration method or not even at 5 keV with 30 nA. Compares to Line (b) and (c), Electron beam deceleration method of line (c) shows better sharpness and details of spectrum than line (b). Probably it is due to smaller probe size was created by electron beam deceleration method. Here we have also tired low voltage condition that is 1 keV with ‐5 keV sample bias in line (a). The line (a) shows much higher spatial resolution line profile due to smaller interaction volume in sold than 5 keV.
Combined stem‐eels and stem‐cl analysis of plasmonic coupling between chemically grown silver nanocubes
Authors: Lourenço Martins Hugo , Lee Yih Hong , Liu Yejing , Lee Hiang Kwee , Kociak Mathieu , Ling Xing Yi 
Published: December 2016

These recent years, study of surface plasmon resonances in transmission electron microscope has undergone an increasing interest. Indeed, low‐loss EELS has proven its remarkable efficiency to probe plasmonic resonances at the nanometer scale while recent developments in cathodoluminescence (CL) spectroscopy brought a new insight into the coupling of plasmons and far field [1]. Several types of particles have already been numerically and experimentally studied ranging from nano‐disk to nano‐prism which plasmonic behaviors are now fairly understood [2,3]. However, despite this systematic effort to characterize the widest variety of plasmonic nano‐particles, some structures still remain challenging e.g. the nano‐cube. In the latest case, the difficulties encountered are plural. First, this structure being highly symmetric, plasmonic modes exhibit a significant number of natural degeneracies leading to superposition or hybridization of modes, which dramatically harden their understanding. Second, cube's plasmonic modes turned out to be very sensitive to the geometry of the underlying nano‐structure (e.g. edge rounding [4]) and to be strongly affected by the presence of substrate [5]. Third, particularly because of the degeneracies mentioned above, the coupling between two nanocubes brings unexpected difficulties, which are enhanced when the inter‐particle gap goes below 1nm. Although this coupling has been widely tackled recently, no definitive theory has been given and this question remains controversial [6,7].
In the present work, we experimentally and numerically investigated plasmonic silver nanocubes and their coupling using STEM‐EEL and STEM‐CL spectroscopies (see figures 1 and 2) aiming at giving a clear and complete understanding of these modes. The cube samples have been prepared by chemical growth, which provides them a high degree of crystallinity. This property dramatically enhance the CL signal and thus enable us to obtain remarkably relevant CL‐maps (see figure 2). For studying the coupling, in order to get rid of the quantum charge transfer problem arising at very small gap regime (<0.5nm), we restricted ourselves to inter‐particle separations larger than 5nm. Complementary BEM simulations [8] have been carried out to understand on a deeper level the observed plasmonic modes by computing the corresponding charge distributions. We observed a good agreement between computations and experiments, which strengthen our conclusion. In addition to be consistent with the earlier studies, our work bring an overall understanding of the nanocubes coupling.