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This paper presents an X-ray reflectivity study of a Sc/SiC/Al periodic multilayer deposited via magnetron sputtering and its possible adaptation to be used as a dispersive element in the crystal spectrometers equipping scanning electron microscopes and electron probe microanalyzers. This multilayer is designed for the spectral range of 45–60 eV. The results reveal a reflectance of 40.8% at 54.1 eV for a near-normal incidence angle of 7° with a narrow bandwidth of 2.6 eV. The measured and simulated reflectivity curves are very close, suggesting that this system has smooth interfaces and low interdiffusion. Owing to the growing importance of lithium and lack of spectroscopic data, we simulate a new Sc/SiC/Al stack based on the reflectivity data and optimize it to perform spectroscopy in the range near the Li K absorption edge around 55 eV, which is in the spectral range of the Li Kα emission band. This optimization is achieved by tuning the thicknesses of the different layers and the number of periods of the multilayer using an in-house Python script. The optimization results are compared with the performances of other multilayers employed in the same energy range and at a working angle close to 30° grazing, including Be/Si/Al. This analysis indicates that the Sc/SiC/Al multilayer could be a good candidate for performing spectroscopy in the Li K range.

Boron carbide is a prominent material for high-brilliance synchrotron optics as it remains stable up to very high temperatures. The present study shows a significant change taking place at 550°C in the buried interface region formed between the Cr adhesive layer and the native oxide layer present on the silicon substrate. An in situ annealing study is carried out at the Indus-1 Reflectivity beamline from room temperature to 550°C (100°C steps). The studied sample is a mirror-like boron carbide thin film of 400 Å thickness deposited with an adhesive layer of 20 Å Cr on a silicon substrate. The corresponding changes in the film structure are recorded using angle-dependent soft X-ray reflectivity measurements carried out in the region of the boron K-edge after each annealing temperature. Analyses performed using the Parratt recursive formalism reveal that the top boron carbide layer remains intact but interface reactions take place in the buried Cr–SiO2 region. After 300°C the Cr layer diffuses towards the substrate. At higher temperatures of 500°C and 550°C the Cr reacts with the native oxide layer and tends to form a low-density compound of chromium oxysilicide (CrSiOx). Depth profiling of Si and Cr distributions obtained from secondary ion mass spectroscopy measurements corroborate the layer model obtained from the soft X-ray reflectivity analyses. Details of the interface reaction taking place near the substrate region of boron carbide/Cr sample are discussed.

Fabrication of wafer-scale nanogratings for X-ray spectroscopy is difficult especially for very high line densities. The authors use vacancy epitaxy to fabricate sub-50-nm-periodicity gratings, coated with multilayers for efficient operation, for use in ultra-high resolution x-ray spectroscopy.

X-ray spectroscopy of lithium is very difficult, even impossible, with wavelength dispersive spectrometers commonly deployed on scanning electron microscopes or electron microprobe analyzers. This is due to the absence of crystals and lack of efficient periodic multilayer for this spectral range, around 50 eV. To address this issue, we propose using a Be/Si/Al multilayer having a period of about 29 nm. The multilayer was deposited by magnetron sputtering and its reflectivity measured as a function of the glancing angle in the spectral range of the Li K emission and as a function of the incident energy up to ~200 eV. This characterization demonstrates that the designed multilayer is suitable to efficiently perform spectroscopy in the range of the Li K emission in terms of reflectance (0.32 at 51.5 eV), bandwidth (around 3.5 eV) and rejection of high order diffracted radiation.

Stimulated emission is a fundamental process in nature that deserves to be investigated and understood in the extreme ultra-violet (EUV) and x-ray regimes. Today, this is definitely possible through high energy density free electron laser (FEL) beams. In this context, we give evidence for soft-x-ray stimulated emission from a magnesium oxide solid target pumped by EUV FEL pulses formed in the regime of travelling-wave amplified spontaneous emission in backward geometry. Our results combine two effects separately reported in previous works: emission in a privileged direction and existence of a material-dependent threshold for the stimulated emission. We develop a novel theoretical framework, based on coupled rate and transport equations taking into account the solid-density plasma state of the target. Our model accounts for both observed mechanisms that are the privileged direction for the stimulated emission of the Mg L2,3 characteristic emission and the pumping threshold.

A study is carried out on the electronic structure of gold nanoparticles embedded in a silica film, both before and after irradiation at 355 nm by a laser. The results show that before irradiation the gold atoms are in metallic states within the nanoparticles.

Electron-induced x-ray emission spectroscopy and cathodoluminescence were used to study alpha-AI2O3 single crystals.

Study of an α-Al[sub 2]O[sub 3] single crystal by electron-induced x-ray emission spectroscopy and cathodoluminescence is reported. The relative intensities of optical emissions due to F[sup +] and F centers have been determined as a function of the parameters of the electron beam and the annealing of the sample. It is shown that the F[sup +] centers, i.e., the oxygen vacancies with one trapped electron, are predominant when the density of the incident electron beam increases. Similar variation is observed when the electron energy varies from 1 to 4 keV. From the comparison between x-ray and optical spectra, the F[sup +] centers are determined to be stable defects in the bulk of the sample. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined electron trapping in the band gap of single-crystal alumina by electron-induced x-ray emission spectroscopy. Defects existing in insulator materials; Results; Discussion.

Pd/Y multilayers are high‐reflectance mirrors designed to work in the 7.5–11 nm wavelength range. Samples, prepared by magnetron sputtering, are deposited with or without B4C barrier layers located at the interfaces of the Pd and Y layers to reduce interdiffusion, which is expected from calculating the mixing enthalpy of Pd and Y. Grazing‐incident X‐ray reflectometry is used to characterize these multilayers. B4C barrier layers are found to be effective in reducing Pd–Y interdiffusion. Details of the composition of the multilayers are revealed by hard X‐ray photoemission spectroscopy with X‐ray standing wave effects. This consists of measuring the photoemission intensity from the samples by performing an angular scan in the region corresponding to the multilayer period and an incident photon energy according to Bragg's law. The experimental results indicate that Pd does not chemically react with B nor C at the Pd–B4C interface while Y does react at the Y–B4C interface. The formation of Y–B or Y–C chemical compounds could be the reason why the interfaces are stabilized. By comparing the experimentally obtained angular variation of the characteristic photoemission with theoretical calculations, the depth distribution of each component element can be interpreted. [ABSTRACT FROM AUTHOR]

Etched multilayers obtained by forming a laminar grating pattern within interferential multilayer mirrors are used in the soft X-ray range to improve the spectral resolution of wavelength dispersive spectrometers equipped with periodic multilayers. We describe the fabrication process of such an etched multilayer dispersive element, its characterization through reflectivity measurement and simulations, and its implementation in a high-resolution Johann-type spectrometer. The specially designed patterning of a Mo/B4C multilayer is found fruitful in the range of the C K emission as the diffraction pattern narrows by a factor 4 with respect to the non-etched structure. This dispersive element with an improved spectral resolution was successfully implemented for electronic structure study with an improved spectral resolution by X-ray emission spectroscopy. As first results, we present the distinction between the chemical states of carbon atoms in various compounds, such as graphite, SiC and B4C, by the different shape of their C K emission band. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We present the results of the characterization of Mg/Co periodic multilayers and their thermal stability for the EUV range. The annealing study is performed up to a temperature of 400C. Images obtained by scanning transmission electron microscopy and electron energy loss spectroscopy clearly show a good quality of the multilayer structure. The measurements of the EUV reflectivity around 25 nm (∼49 eV) indicate that the reflectivity decreases when the annealing temperature increases above 300C. X-ray emission spectroscopy is performed to determine the chemical state of the Mg atoms within the Mg/Co multilayer. Nuclear magnetic resonance used to determine the chemical state of the Co atoms and scanning electron microscopy images of cross sections of the Mg/Co multilayers reveal changes in the morphology of the stack from an annealing temperature of 305C. This explains the observed reflectivity loss. [ABSTRACT FROM AUTHOR]

Abstract: A methodology combining non-destructive X-ray techniques is proposed to study the interfacial zones of periodic multilayers. The used X-ray techniques are X-ray emission spectroscopy induced by electrons and X-ray reflectivity in the hard and soft X-ray ranges. The first technique evidences the presence of compounds at the interfaces and gives an estimation of the thickness of the interfacial zone. These informations are used to constrain the fit of the X-ray reflectivity curves that enables to determine the thickness and roughness of the various layers of the stacks. The results are validated in the soft X-ray range where the reflectivity curves are very sensitive to the chemical state of the elements present in the stack. The methodology is applied to characterize Mo/Si (1–4nm/2nm) and B4C/Mo/Si (1nm/2nm/2nm) multilayers. It is shown that the two interfacial zones of the Mo/Si multilayers are composed of the silicides MoSi2 and Mo5Si3. It is found that the interface thickness is about to be 0.4–0.8nm depending on the samples. The molybdenum silicides are also evidenced at the interfaces of the B4C/Mo/Si multilayers. However, their interface thickness is 0.2nm thinner than that of the same stack without the B4C layers, these layers being at the Mo-on-Si side or at the Si-on-Mo side. Thus, the B4C layers do not stop but only reduce the interdiffusion between the Mo and Si layers. [Copyright &y& Elsevier]