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A closer look at catalysis: In situ hard X‐ray nanotomography has been developed (see picture) as a method to investigate an individual iron‐based Fischer–Tropsch‐to‐Olefins (FTO) catalyst particle at elevated temperatures and pressures. 3D and 2D maps of 30 nm resolution could be obtained and show heterogeneities in the pore structure and chemical composition of the catalyst particle of about 20 μm.

Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continumicrom XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet.

The magnetic domain structure in Permalloy (Ni81Fe19) micropatterns (10?100??m) on NiO has been investigated by means of soft x-ray photoemission electron microscopy. The exchange anisotropy between the Ni81Fe19 patterns and the NiO layer results in the formation of complex domain structures which markedly differ from the simple Landau?Lifshitz configurations. The domain structures reflect the competition between the exchange anisotropy and the dipole?dipole interaction in a weakly coupled system. The observed domain structures change with the feature size, as the domain patterns lose complexity in the smaller structures.

Two powerful and complementary techniques for chemical characterisation of nanoscale systems are electron energy-loss spectroscopy in the scanning transmission electron microscope, and X-ray absorption spectroscopy in the scanning transmission X-ray microscope. A correlative approach to spectro-microscopy may not only bridge the gaps in spatial and spectral resolution which exist between the two instruments, but also offer unique opportunities for nanoscale characterisation. This review will discuss the similarities of the two spectroscopy techniques and the state of the art for each microscope. Case studies have been selected to illustrate the benefits and limitations of correlative electron and X-ray microscopy techniques. In situ techniques and radiation damage are also discussed.

Self-assembled colloidal crystals have attracted major attention because of their potential as low-cost three- dimensional (3D) photonic crystals. Although a high degree of perfection is crucial for the properties of these materials, little is known about their exact structure and internal defects. In this study, we use tomographic scanning transmission X-ray microscopy (STXM) to access the internal structure of self- assembled colloidal photonic crystals with high spatial resolution in three dimensions for the first time. The positions of individual particles of 236 nm in diameter are identified in three dimensions, and the local crystal structure is revealed. Through image analysis, structural defects, such as vacancies and stacking faults, are identified. Tomographic STXM is shown to be an attractive and complementary imaging tool for photonic materials and other strongly absorbing or scattering materials that cannot be characterized by either transmission or scanning electron microscopy or optical nanoscopy.

Photonic crystals consisting of nano- to micrometer-sized building blocks, such as multiple sorts of colloids, have recently received widespread attention. It remains a challenge, however, to adequately probe the internal crystal structure and the corresponding deformations that inhibit the proper functioning of such materials. It is shown that scanning transmission X-ray microscopy (STXM) can directly reveal the local structure, orientations, and even deformations in polystyrene and silica colloidal crystals with 30-nm spatial resolution. Moreover, STXM is capable of imaging a diverse range of crystals, including those that are dry and inverted, and provides novel insights complementary to information obtained by benchmark confocal fluorescence and scanning electron microscopy techniques.

The present status of in-situ scanning transmission X-ray microscopy (STXM) is reviewed, with an emphasis on the abilities of the STXM technique in comparison with electron microscopy. The experimental aspects and interpretation of X-ray absorption spectroscopy (XAS) are briefly introduced and the experimental boundary conditions that determine the potential applications for in-situ XAS and in-situ STXM studies are discussed. Nanoscale chemical imaging of catalysts under working conditions is outlined using cobalt and iron Fischer-Tropsch catalysts as showcases. In the discussion, we critically compare STXM-XAS and STEM-EELS (scanning transmission electron microscopy-electron energy loss spectroscopy) measurements and indicate some future directions of in-situ nanoscale imaging of catalytic solids and related nanomaterials.

We show that a photoelectron spectromicroscope of the photoelectron emission microscope type can be used as an x-ray imaging detector for radiology. Using high penetration hard-x-ray photons (wavelength < 0.1 nm), samples as thick as a few millimeters can be imaged with submicron resolution. The high imaging resolution enables us to substantially decrease the object-detector distance needed to observe coherent based contrast enhancement with respect to the standard film-based detection technique. Our result implies several advantages, the most important being a marked reduction of the required source emittance for contrast enhanced radiology. (C) 1999 American Institute of Physics. [S0003-6951(99)00842-6].

We report a pilot study in in situ electrochemical X-ray dynamic microscopy, based on a model system: the anodic and cathodic behaviour of Ag in neutral NaCl and (NH4)2SO4 aqueous solutions. In situ X-ray imaging highlighted mesoscopic features related to corrosion processes, yielding soluble (NH4+ solution) and insoluble (Cl− solution) corrosion products, as well as cathodic growth morphologies. X-ray absorption and phase contrast images were collected, confirming the feasibility of soft X-ray microscopic measurements with lateral resolution down to a few tens of nm in electrochemical cells for operation in a high vacuum environment in presence of liquid electrolytes. Keywords: Soft X-rays, Spectromicroscopy, Silver

Spectromicroscopy with the imaging technique of X-ray photoelectron emission microscopy (X-PEEM) is a microchemical analytical tool installed in many synchrotron radiation laboratories, and which is finding application in diverse fields of research. The method of sample analysis, X-ray absorption spectroscopy, does not encounter the same problems as X-ray photoemission spectroscopy when sample charging occurs, hence even good insulators may often be analyzed without any apparent artifacts in images or spectra, We show, however, that charging effects cannot be neglected. We model the effect of surface charge formation on the secondary electron yield from uniform samples to demonstrate that surface charge primarily reduces the yield of electrons which may contribute to the detected signal. We illustrate that on non-uniform insulating samples, localized centers of charge may substantially affect microscope imaging and resolution as the electrostatic held close to the surface is distorted. Finally, in certain circumstances non-uniform surface charge may lead to unexpected lineshapes in X-fay absorption spectra causing, in some extreme cases, negative spectra, These negative spectra are explained, and several strategies are reviewed to minimize the impact of sample charging when analyzing poorly conducting samples of any nature. (C) 2000 Elsevier Science B.V. All rights reserved.

Photoelectron spectromicroscopy, the combination of conventional photoelectron spectroscopy and high lateral resolution, is a novel technique that exploits the high brightness of the most recent synchrotron sources. We briefly review its main implementation modes and present some examples of applications, with particular emphasis on semiconductor interface research.

We show that photoelectron spectromicroscopy with synchrotron radiation has been successfully exported from materials science to the life sciences. The transfer is well beyond mere feasibility tests. Photoelectron spectromicroscopy is in fact used for real, long-term studies in neurobiology. Specific examples are discussed, first to see in practice some applications to microchemical analysis of physiologic elements, and then to discuss present and future instrumentation development issues. This last point is illustrated by briefly presenting the MEPHISTO project and the CERVIN project for the Swiss Light Source. (C) 1997 Elsevier Science B.V.

Far-field fluorescence spectromicroscopy of single quantum emitters (SQEs) (single molecules, quantum dots, color centers in crystals) is an actively developing field of modern photonics, which is in widespread demand in various applications in physics, chemistry, material sciences, life sciences, and quantum technologies. In this paper, we present a description of a multifunctional experimental setup which was developed in recent years at the Institute for Spectroscopy of the Russian Academy of Sciences. It allows measuring optical spectra and fluorescence images of SQEs, as well as their temporal behavior and luminescence kinetics, in a broad range of temperatures (from cryogenic to ambient). It is shown that the spatial coordinates of SQEs can be reconstructed with subdiffractional accuracy (up to a few angstroms). Some examples of the developed methods for multiparameter superresolution microscopy (nanoscopy) of materials and nanostructures are presented.

Synchrotron-light-based microscopic interface characterization techniques have been a major factor in the progress towards the understanding control of interface properties and performances. Their role was recently enhanced by the advent of third-generation ultrabright sources. Such superior sources expand the performances and application domains of traditional spectroscopy and microscopy techniques. This point will be illustrated with a series of recent examples produced by ELETTRA in Trieste, Italy; the examples concern high-resolution spectroscopy, spectromicroscopy and time-resolved spectroscopy. Finally, we will discuss the exciting applications which exploit the source coherence to achieve superior imaging with X-rays. (C) 1998 Elsevier Science B.V. All rights reserved.

1993 has been full of landmarks for interface research: the new ultrabright soft X-ray synchrotron sources ALS-Berkeley, ELETTRA-Trieste and SRRC-Taiwan, and the user operation of the free electron laser (FEL) at Vanderbilt. They are particularly important for the increasing use of lateral resolution in photoemission, and for the first use of FEL spectroscopy. We review some recent results: the discovery of lateral band-bending changes of cleaved III-V's; [1] Gozzo et al.'s observation of spatially-varying barriers at Schottky [2] and heterojunction [3] interfaces; Cerrina et al.'s photoelectron micrographs of homojunctions; [4] Coluzza er al.'s evidence that many of the conventional photoemission spectra of insulators are heavily affected by local charging [5]. As to the FEL, we will present the two-photon absorption at the indirect Ge gap [6], and Coluzza er al.'s accurate and reliable measurements of energy barriers at ''buried'' interfaces with internal photoemission [7].

EXPERIMENTAL evidence of the preferential uptake of aluminium by GABAergic neurones and glial cells was provided by synchrotron spectromicroscopy studies. We observed rat cerebellar cultures enriched for GABAergic neurones or glial cells exposed to aluminium ions, detecting the presence and identifying the chemical status of aluminium on cell structures.