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The microstructural evolution during the uniaxial compression of an as-deposited bulk nanocrystalline (nc) Ni–Fe (average grain size d≈23nm) at ambient temperature was investigated by the high-energy x-ray diffraction (HEXRD) and the transmission-electron microscopy (TEM). HEXRD measurements indicated that the grain growth occurred in the nc Ni–Fe alloy during the uniaxial compression tests and that the grain growth shows orientation dependence, i.e., the grains preferentially grow perpendicular to the loading direction. This preferred grain growth was further confirmed by the TEM observations, indicating that the grains were elongated after the compressive plastic deformation.

The temperature dependent Schottky diode characteristics of epitaxial junctions between Nb:SrTiO3 (Nb concentrations: 0.5%) and Fe3O4 are studied. Epitaxial thin films of Fe3O4 were grown on Nb:SrTiO3 substrates by pulsed laser deposition technique. The films and heterointerfaces were characterized by x-ray diffraction, Z-contrast transmission electron microscopy, magnetic susceptibility, four-probe in-plane resistivity, and the temperature dependent junction current-voltage (I‐V) characteristics. The nonlinear nature of the characteristics is analyzed within the framework of thermionic emission theory. Junction parameters such as the Schottky barrier height (ϕB) and ideality factor (η) are extracted. The temperature evolution of these parameters shows interesting and systematic trends, with remarkable changes near the Verwey transition (TV=120K). The magnetic field dependence of I‐V characteristic data is also recorded and a spin polarization of ∼80% is estimated for the magnetite electrode.

We report on the search for ferromagnetism in undoped and cobalt-doped high-k dielectric HfO2 films. Over a broad range of growth conditions, we do not observe ferromagnetism in undoped HfO2 films. On the other hand, we do observe room temperature ferromagnetism in dilutely Co-doped HfO2 films, but the origin of the same appears extrinsic (a Co rich surface layer) at least for the regime of growth conditions explored.

We report on the fabrication and electrical characterization of epitaxial metal-semiconductor junctions between Y1Ba2Cu3O7−δ (YBCO) (optimally doped and Zn doped) and (001) Nb:SrTiO3 with different Nb concentrations (0.05%, 0.1%, and 0.5%). The current-voltage characteristics of such epitaxial junctions are nonlinear and rectifying, and these are dramatically enhanced with decreasing Nb concentration and Zn doping. Indeed, for the case of 0.05% Nb:STO, reverse breakdown voltage as high as −18V(−28V) is realized for optimally doped (Zn doped) YBCO. These data are analyzed within the framework of thermionic emission∕diffusion models for Schottky and metal-insulator-semiconductor-type junctions.

Nanoscale intergranular films in doped silicon-nitride ceramics are known to markedly affect toughness and creep resistance. They are regarded as being fully amorphous, but are shown here to have a semicrystalline structure in a Ce-doped Si3N4. Using two different but complementary high-resolution electron-microscopy methods, the intergranular atomic structure, imaged with sub-angstrom resolution, reveals that segregated cerium ions take very periodic positions, along the intergranular-phase∕matrix-grain interface and as a semicrystalline structure spanning the width of the intergranular phase. This result has broad implications for the understanding of the structure and role of the intergranular phase in enhancing the mechanical properties of ceramics.

It is shown that dilute niobium doping has significant effect on the ferromagnetism and microstructure of dilutely cobalt-doped anatase TiO2 films. Epitaxial films of anatase TiO2 with 3% Co, without and with 1% niobium doping were grown by pulsed-laser deposition at 875 C at different oxygen pressures. For growth at 10^{-5} Torr niobium doping suppresses the ferromagnetism, while it enhances the same in films grown at 10^{-4} Torr. High-resolution Z-contrast Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy show uniform surface segregation of cobalt-rich Ti_{1-x-y}Co_{x}Nb_{y}O_{2-d} phase, but without cobalt metal clusters., Comment: 17 pages, 3 figures

Electron energy loss spectroscopy (EELS) is ideally suited for the study of oxide materials. The large cross section for the oxygen K-absorption edge generates enough signal for fine-structure analysis even when the probe is small enough for atomic resolution imaging (∼2Å). Therefore, by using the Z-contrast imaging technique in the STEM to locate defects and position the probe with atomic resolution, detailed spectroscopic information can be obtained from a known atomic location. by selecting the appropriate acquisition conditions, these spectra can have the same atomic resolution and incoherent features as the Z-contrast image. The primary benefit of this methodology is that the image provides a structural model for interpretation of the spectrum through theoretical modeling.One means of interpreting this spectral fine-structure is through multiple scattering analysis. In the multiple scattering formulation, the fine-structure of the absorption edge is considered to arise from interference effects resulting from the scattering of an excited photoelectron from neighboring atoms.

The short coherence length in high-Tc superconductors (5-15Å) makes an atomic scale understanding of the electronic properties at defects and interfaces essential for device applications. This understanding is particularly relevant for grain boundaries in YBa2CU3O7-δ (YBCO), where although extensive studies have shown a clear exponential decrease in critical current with misorientation angle, the absolute value can vary by several orders of magnitude at any given misorientation angle.Figure 1 shows Z-contrast images of an [001] low-angle tilt boundary and a 30° [001] asymmetric tilt grain boundary. An interesting feature of both of these boundaries is that there appear to be sites where two atom columns are too close together. However, the problem of like-ion repulsion can be avoided if the columns are taken to be partially occupied. Insight into the effect of this partial occupancy can be obtained through the use of bond-valence sum analysis. Here, the formal valence of an atom is made up of contributions from all of its nearest neighbors, the magnitude of which are determined by the bond length.

We report on the growth of highly oriented HfO2 thin films of monoclinic phase stabilized by 5% Co doping on (001) yttrium-stabilized zirconia (YSZ) using pulsed-laser deposition at 700°C at an oxygen partial pressure of 10−4Torr. On the other hand, pure HfO2 of such quality did not grow on YSZ in wide range of growth parameters. Rutherford backscattering-ion channeling in this film showed a 24% minimum yield (χmin) indicating highly oriented film growth, while hardly any ion channeling was observed in the undoped sample. High-resolution transmission electron microscopy revealed a sharp interface, and no signature of Co clusters. Electron energy loss spectroscopy showed that Co is in the 2+ state. Attempts were also made to grow films on a (001) Si substrate, and the results showed a very low ion channeling yield (∼8%).

The simultaneous use of Z-contrast imaging with parallel detection EELS in the STEM provides a powerful means for determining the atomic structure of grain boundaries. The incoherent Z-contrast image of the high atomic number columns can be directly inverted to their real space arrangement, without the use of preconceived structure models. Positions and intensities may be accurately quantified through a maximum entropy analysis. Light elements that are not visible in the Z-contrast image can be studied through EELS; their coordination polyhedra determined from the spectral fine structure. It even appears feasible to contemplate 3D structure refinement through multiple scattering calculations.The power of this approach is illustrated by the recent study of a series of SrTiC>3 bicrystals, which has provided significant insight into some of the basic issues of grain boundaries in ceramics. Figure 1 shows the structural units deduced from a set of 24°, 36° and 65° symmetric boundaries, and 24° and 45° asymmetric boundaries. It can be seen that apart from unit cells and fragments from the perfect crystal, only three units are needed to construct any arbitrary tilt boundary. For symmetric boundaries, only two units are required, each having the same Burgers, vector of a. Both units are pentagons, on either the Sr or Ti sublattice, and both contain two columns of the other sublattice, imaging in positions too close for the atoms in each column to be coplanar. Each column was therefore assumed to be half full, with the pair forming a single zig-zag column. For asymmetric boundaries, crystal geometry requires two types of dislocations; the additional unit was found to have a Burgers’ vector of a. Such a unit is a larger source of strain, and is especially important to the transport characteristics of cuprate superconductors. These zig-zag columns avoid the problem of like-ion repulsion; they have also been seen in TiO2 and YBa2Cu3O7-x and may be a general feature of ionic materials.

Atomic scale effects at grain boundaries are known to play a dominant role in controlling the bulk properties of many materials. However, a detailed understanding of this role is complicated by the tendency for boundaries to behave in a “non-ideal” manner, i.e. the boundary plane can change on the scale of a few nanometers, altering the number of vacancies and impurities and the presence of second phases. The crucial first step to engineering boundary properties is therefore the ability to observe these changes experimentally with both atomic resolution and sensitivity. Such a capability is provided by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM).The Z-contrast technique generates an incoherent, atomic resolution structural image of a grain boundary which can be used to position the electron probe with atomic precision for spectroscopy. As the spectrum has nearly the same resolution as the image for core-losses >100eV, this arrangement has the unique advantage of allowing compositional fluctuations to be correlated directly with structural features in the boundary plane. Furthermore, multiple-scattering (MS) analysis can be utilized to extract 3- dimensional structural information from the spectrum. MS techniques consider the fine-structure of the spectrum to arise from interference effects occurring when a photoelectron created during the energy loss process is reflected from neighboring atoms. The real-space clusters used in this methodology allow the flexibility to determine whether the contributions to the spectrum arise from single or multiple scattering paths and from which atomic neighbors they originate. This allows the different structural relaxations that occur at boundaries, i.e. vacancies or structural disorder, to be distinguished from the spectrum.

Materials properties associated with interfaces and defects are dominated by atomic scale fluctuations in composition, structure and bonding. Although electron energy loss spectroscopy (EELS) provides a powerful tool to probe these features, low signal, lens aberrations, image coherence and specimen drift preclude the use of spectrum imaging and energy filtered imaging for these high-resolution problems. However, by utilizing Z-contrast imaging in conjunction with EELS in the scanning transmission electron microscope (STEM), these limitations are largely overcome and EELS appears capable of providing fudamental 3-D characterization of defect and interface structures with atomic resolution and sensitivity.The main premise in utilizing these combined techniques is that the properties of defects and interfaces must be associated with structural differences relative to the bulk. If those structural differences can be located, then it is only necessary to perform spectroscopy in their vicinity to understand the structure property relationship. For crystalline materials in zone-axis orientations, the Z-contrast image provides this atomic resolution structural map. As this direct image is generated with only the high-angle scattering, it can be used to position the electron probe with atomic precision and does not interfere with the low-angle scattering for spectroscopy.

Combining atomic-resolution imaging with spatially resolved electron energy loss spectroscopy (EELS) is a powerful approach to probing the geometric, chemical and electronic aspects of internal interfaces. By elucidating these interrelated constituents of interface structure, one can begin to understand the influence of the interface atomic structure on relevant bulk material properties, deducing atomic structure/property relationships. The combined Z-contrast and EELS approach was applied to two types of heterophase interfaces: oxide-oxide (NiO-ZrO2) and metal-oxide (Ni-ZrO2). The interface structure will be discussed in light of these experiments and compared to previous HREM results.

High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted intuitively without the need for preconcieved atomic structure models. Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale. The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface. In this paper we use the complimentary techniques of high resolution Z-contrast imaging and PEELS to investigate the atomic structure and chemistry of a 25 degree symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.Figure 1(a) shows a Z-contrast image of a symmetric region of the tilt boundary. The brightest spots in the image correspond to the increased scattering power of the Sr atomic columns (Z=38) with theless bright spots corresponding to the Ti atomic columns (Z=22). The lighter O atomic columns are notvisible in a Z-contrast image.

The recent development of the Z-contrast imaging technique for the VG HB501 UX dedicated STEM, has added a high-resolution imaging facility to a microscope used mainly for microanalysis. This imaging technique not only provides a high-resolution reference image, but as it can be performed simultaneously with electron energy loss spectroscopy (EELS), can be used to position the electron probe at the atomic scale. The spatial resolution of both the image and the energy loss spectrum can be identical, and in principle limited only by the 2.2 Å probe size of the microscope. There now exists, therefore, the possibility to perform chemical analysis of materials on the scale of single atomic columns or planes.In order to achieve atomic resolution energy loss spectroscopy, the range over which a fast electron can cause a particular excitation event, must be less than the interatomic spacing. This range is described classically by the impact parameter, b, which ranges from ~10 Å for the low loss region of the spectrum to

Communication assemblies between biomimetic nanocapsules in a 3D closed system with self-regulating and self-organization functionalities were demonstrated for the first time. Two types of biomimetic nanocapsules, TiO2/polydopamine capsules and SiO2/polyelectrolytes capsules with different stimuli-responsive properties were prepared and leveraged to sense the external stimulus, transmit chemical signaling, and autonomic communication-controlled release of active cargos. The capsules have clear core–shell structures with average diameters of 30 nm and 25 nm, respectively. The nitrogen adsorption–desorption isotherms and thermogravimetric analysis displayed their massive pore structures and encapsulation capacity of 32% of glycine pH buffer and 68% of benzotriazole, respectively. Different from the direct release mode of the single capsule, the communication assemblies show an autonomic three-stage release process with a “jet lag” feature, showing the internal modulation ability of self-controlled release efficiency. The control overweight ratios of capsules influences on communication-release interaction between capsules. The highest communication-release efficiency (89.6% of benzotriazole) was achieved when the weight ratio of TiO2/polydopamine/SiO2/polyelectrolytes capsules was 5 : 1 or 10 : 1. Communication assemblies containing various types of nanocapsules can autonomically perform complex tasks in a biomimetic fashion, such as cascaded amplification and multidirectional communication platforms in bioreactors., The assemblies of biomimetic nanocapsules can exhibit self-regulating, self-organization functionalities involving internal modulation of self-controlled release by the dynamic stimuli-response-communication-decide-response behaviour.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

Gallium nitride powders and zinc oxide powders were each calcined with a few weight percent of copper oxide and/or magnesium oxide either in air or N2. Powder X-ray diffractometry, transmission electron microscopy, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy were performed in order to observe calcination induced structural effects on these wurtzite type semiconductors. We note that our earlier magnetic results on Cu doped GaN are qualitatively consistent with recent first principle calculations [Wu et al., Appl. Phys. Lett. 89 (2006) 62505].

Here we report a strategy for the growth of single crystal heterostructures that dramatically reduces the nucleation of defects at the film–substrate interface. The substrate surface is patterned through miscut and passivated to enable a single domain template layer to be grown. This template is incommensurate with, and weakly bonded to, the substrate. A single domain film can then be nucleated preferentially at step edges and grown on the template. This mechanism is demonstrated for CdTe on Si(100) and should be applicable to many other systems.

Gd3+ doped Ce oxides are a major candidate for use as the electrolyte in solid oxide fuel cells operating at ∼500 °C. Here, the effect of the atomic structure on the local electronic properties, i.e. oxygen coordination and cation valence, at grain boundaries in the fluorite structured Gd0.2Ce0.8O2-x ceramic electrolyte is investigated by a combination of atomic resolution Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). In particular, EELS analyses from grain boundaries reveals a complex interaction between segregation of the dopant (Gd3+), oxygen vacancies and the valence state of Ce. These results are similar to observations from fluorite-structured Yttria-Stabilized Zirconium (YSZ) bicrystal grain boundaries.

Polarization fatigue with repeated electric cycles in ferroelectric thin films is a major degradation problem in ferroelectric nonvolatile memories. However, the origin of this phenomenon is still not properly understood. The fatigue mechanism of a ferroelectric perovskite in a multilayer ferroelectric PbTiO3 thin film material has been investigated here using scanning transmission electron microscopy (STEM). Z-contrast images of the interfaces show that the ferroelectric PbTiO3 layer has partly decomposed into a single crystal PbTiO3 layer and an amorphous layer. Nanometer-sized precipitates are present near the Pt electrode. Electron energy-loss spectroscopy (EELS) analysis reveals that the amorphous layer is a Ti-rich phase between TiO2 and PbTiO3. The precipitates are determined to be a Pt-Pb rich crystalline phase. It is suggested that the formation of the structure-distorted intermediate layer and precipitates may be associated with the ferroelectric degradation process by acting as a passive layer in a ferroelectric capacitor. In addition, the formation of the Pt-Pb rich precipitates may cause an interruption of the consistent Pt electrode, which may result in failure of the device.

The nucleation and growth of Hg1−xCdxTe on CdTe(211)B/Si(211) substrates by molecular beam epitaxy are comprehensively studied by in situ reflection high energy electron diffraction and transmission electron microscopy. Microtwins are observed to be formed at the interface, but are overgrown later as the growth proceeds. It is shown that the three-dimensional growth at the nucleation stage of HgCdTe on CdTe(211)B/Si and CdZnTe(211)B is more likely due to the higher surface energy of Hg1−xCdxTe than that of CdTe(211)B and CdZnTe(211)B.

In situ scanning transmission electron microscopy is being developed for numerous applications in the study of nucleation and growth under electrochemical driving forces. For this type of experiment, one of the key parameters is to identify when nucleation initiates. Typically, the process of identifying the moment that crystals begin to form is a manual process requiring the user to perform an observation and respond accordingly (adjust focus, magnification, translate the stage, etc.). However, as the speed of the cameras being used to perform these observations increases, the ability of a user to “catch” the important initial stage of nucleation decreases (there is more information that is available in the first few milliseconds of the process). Here, we show that video shot boundary detection can automatically detect frames where a change in the image occurs. We show that this method can be applied to quickly and accurately identify points of change during crystal growth. This technique allows for automated segmentation of a digital stream for further analysis and the assignment of arbitrary time stamps for the initiation of processes that are independent of the user’s ability to observe and react. Electronic supplementary material The online version of this article (doi:10.1186/s40679-016-0034-x) contains supplementary material, which is available to authorized users.

The atomic-scale structure, composition, and chemistry of grain boundaries in two fluorite-structured ceramic materials were characterized by a combination of Z-contrast imaging and electron energy-loss spectroscopy (EELS). In the case of a symmetric 24° [001] tilt bicrystal of yttria-stabilized-zirconia (YSZ), a shift in the zirconium M-edge onset and a change in the yttrium and zirconium M-edge ratios at the boundary indicate an increase in the number of electrons in the boundary plane. A detailed study of the structure and composition indicates that this is caused by an increase in the number of oxygen vacancies in the grain boundary core that is partially compensated by yttrium segregation. Studies of grain boundaries in an industrial Gd-doped ceria ceramic reveals similar changes in vacancy/dopant profiles indicating that these effects may be generic to grain boundaries in fluorite-structured materials.

Many microscopic investigations of materials may benefit from the recording of multiple successive images. This can include techniques common to several types of microscopy such as frame averaging to improve signal-to-noise ratios (SNR) or time series to study dynamic processes or more specific applications. In the scanning transmission electron microscope, this might include focal series for optical sectioning or aberration measurement, beam damage studies or camera-length series to study the effects of strain; whilst in the scanning tunnelling microscope, this might include bias-voltage series to probe local electronic structure. Whatever the application, such investigations must begin with the careful alignment of these data stacks, an operation that is not always trivial. In addition, the presence of low-frequency scanning distortions can introduce intra-image shifts to the data. Here, we describe an improved automated method of performing non-rigid registration customised for the challenges unique to scanned microscope data specifically addressing the issues of low-SNR data, images containing a large proportion of crystalline material and/or local features of interest such as dislocations or edges. Careful attention has been paid to artefact testing of the non-rigid registration method used, and the importance of this registration for the quantitative interpretation of feature intensities and positions is evaluated.

A combination of experiments and theoretical calculations is used to develop an atomic-scale model of the grain boundary potential in perovskite oxides. More specifically, pristine 8° and 58° [001] tilt grain boundaries in SrTiO 3 , which can be regarded as model systems for all cubic perovskite systems, are examined by Z-contrast imaging and electron-energy-loss spectroscopy. Based on results obtained from these systems, distance-valence least-square analysis and multiple-scattering calculations are used to determine the density of grain boundary states for the 8° and 58° grain boundaries, respectively. To compute the grain boundary potentials, the Thomas-Fermi approach of screened charges and the classical Schottky model is used. The validity of both models for various perovskite oxide grain boundary configurations is discussed, and the appropriate grain boundary potentials are compared with previously reported data.

Gallium nitride powders were calcined with copper oxide in either air or N2 and analyzed by means of powder X-ray diffraction (XRD), high-resolution parallel illumination (HRTEM) and scanning probe transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS) in order to address the structural and electronic effects of Cu-incorporation into GaN. Gallium oxide and multiple copper oxide phases corresponding to the calcination environment were detected. Significant changes in the lattice parameters and electronic structure of the N2-processed GaN indicate incorporation of both copper and oxygen into the GaN lattice as well as changes in the chemical bonding due to the calcinations process. SQUID magnetometer measurements at 300 K demonstrated ferromagnetism in selected samples.

It is just over one hundred years since Lord Rayleigh first showed the differences between coherent and incoherent imaging in the light microscope, pointing out the advantages of the latter for resolution and image interpretation. The annular detector in the high-resolution STEM provides the same advantages for electrons, allowing incoherent imaging at atomic resolution, with image contrast strongly dependent on atomic number (Z). Since incoherent imaging has no phase problem, these Z-contrast images may be directly inverted to give the (projected) atomic positions. A maximum entropy method avoids false detail associated with direct deconvolution, and gives atomic coordinates to an accuracy of ± 0.1 Å. Electron energy loss spectroscopy can provide valuable complementary information on light element bonding and the presence of impurities in specific atomic planes selected from the image. Together, these techniques have revealed some surprisingly complex interfacial structures. For surface studies, the 1.3 A probe of the VG Microscopes HB603U STEM provides sufficient penetration and contrast to image single Pt and Rh atoms on γ-alumina supports. Such images reveal preferred atomic configurations, and allow possible surface adsorption sites to be deduced.

The macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted directly without the need for preconceived atomic structure models (1). Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale (2). The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface (3). In this paper we use the complimentary techniques of high resolution Zcontrast imaging and PEELS to investigate the atomic structure and chemistry of a 25° symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.

We demonstrate the growth of large-area, domain-free CdTe(111)B single crystals on As-passivated Si(111) substrates by molecular beam epitaxy using ZnTe buffer layers. The crystal quality of the CdTe(111)B/ZnTe(111)B/Si(111) films was examined by x-ray diffraction (56 arcs), etch-pit-density (2×105 cm−2) analysis, and transmission electron microscopy, and was found to be comparable to or better than the best CdTe(111)B films grown directly on vicinal Si(001). Surface reconstructions were observed by reflection high-energy electron diffraction at different stages. Diffraction intensity oscillations demonstrated the layer-by-layer growth mode of the CdTe surface. An interface model for these films is proposed.

In this study we have grown epitaxial layers of wurtzite–CdS on CdTe( 1 1 1 )B/Si substrates using molecular beam epitaxy. Indium was used to obtain n-type doping of CdS. The concentration and uniformity of In was determined by secondary ion mass spectrometry (SIMS). Indium profiles were obtained for concentrations ranging from 5×1017 to 1.4×1021 cm−3 and agree well with the variation expected from the In flux.

Understanding the fundamental processes taking place at the electrode-electrolyte interface in batteries will play a key role in the development of next generation energy storage technologies. One of the most fundamental aspects of the electrode-electrolyte interface is the electrical double layer (EDL). Given the recent development of high spatial resolution in-situ electrochemical fluid cells for scanning transmission electron microscopy (STEM), there now exists the possibility that we can directly observe the formation and dynamics of the EDL. In this paper we predict electrolyte structure within the EDL using classical models and atomistic Molecular Dynamics (MD) simulations. Classical models are found to greatly differ from MD in predicted concentration profiles. It is thus suggested that MD must be used in order to accurately predict STEM images of the electrode-electrolyte interface. Using MD and image simulation together for a high contrast electrolyte (the high atomic number CsCl electrolyte), it is determined that, for a smooth interface, concentration profiles within the EDL should be visible experimentally. When normal experimental parameters such as rough interfaces and low-Z electrolytes (like those used in Li-ion batteries) are considered, observation of the EDL appears to be more difficult.

One of the main limitations of imaging at high spatial and temporal resolution during in-situ transmission electron microscopy (TEM) experiments is the frame rate of the camera being used to image the dynamic process. While the recent development of direct detectors has provided the hardware to achieve frame rates approaching 0.1 ms, the cameras are expensive and must replace existing detectors. In this paper, we examine the use of coded aperture compressive sensing (CS) methods to increase the frame rate of any camera with simple, low-cost hardware modifications. The coded aperture approach allows multiple sub-frames to be coded and integrated into a single camera frame during the acquisition process, and then extracted upon readout using statistical CS inversion. Here we describe the background of CS and statistical methods in depth and simulate the frame rates and efficiencies for in-situ TEM experiments. Depending on the resolution and signal/noise of the image, it should be possible to increase the speed of any camera by more than an order of magnitude using this approach.Mathematics Subject Classification: (2010) 94A08 · 78A15

Theo scanning transmission electron microscope can now routinely produce a probe of atomic dimensions, 2.2Å at 100 kV and 1.3Å at 300 kV. This capability opens up a new strategy for determining the structure and bonding of materials at the atomic scale, which is particularly advantageous for complex interfaces such as grain boundaries. The Z-contrast image allows the high-Z column locations to be determined by direct inspection, and quantified through maximum entropy methods to a positional accuracy of currently ~0.2Å. With the same electron probe, located to sub-Ångstrom precision with reference to the Z-contrast image, parallel detection EELS can determine light element coordination from core edge fine structure, in principle around a single atomic column.The attractive features of this approach are the increased resolution associated with incoherent imaging, 0.44 Cs1/4 λ3/4 compared with 0.66 Cs1/4 λ3/4 for phase contrast imaging, and the highly local nature of the image, which makes possible a greatly extended regieme of intuitive image interpretation, and also permits column-by-column spectroscopy without beam broadening.