Multifitting: software for the reflectometric reconstruction of multilayer nanofilms

Al/Zr-based multilayer mirrors with record-breaking reflectivity

The paper reports on a new Zr/Be/Si/Al multilayer structure that provides record reflectances of up to 67% and a spectral resolution of Δλ = 0.63 nm (λ / Δλ ≈ 27) in the spectral range of 17-20 nm. It is shown that the structure has a high temporal stability of extreme ultraviolet (EUV) optical characteristics. This fact makes the structure promising for future missions to study the solar corona.

Effects of interface-engineering on the internal structure and reflective characteristics of Cr/Sc multilayer mirrors

Record reflectivity's of REXP=23.8% at 3.14 nm and RCALC=30.8% at 3.12 nm have been obtained for Cr/Sc mirrors. Such increases in reflection are the result of decreases in mixing of the system layers with each other due to the use of interface-engineering methods - passivation of the already deposited Cr layer with nitrogen before deposition of the subsequent Sc layer. However, it has been found that adding additional B4C layers to such a system leads to a decrease in reflectivity.

Stress, reflectance, and stability of Ru/Be multilayer coatings with Mo interlayers near the 11 nm wavelength

The stress, reflectance, and temporal stability of Ru/Be multilayer mirrors, both with and without Mo interlayers, were studied. A Ru/Be MLM was found to have zero stress at a Ru layer thickness-to-period ratio of γ ∼ 0.4. By adding Mo interlayers to both interfaces, it is possible to achieve a record-high reflectance (R > 71%) at a wavelength close to 11 nm while maintaining near-zero stress levels. A Ru/Be MLM with Mo interlayers at both interfaces also demonstrates high temporal reflectance stability. Ru/Be MLMs may be of interest for the next-generation projection lithography at a wavelength of 11.2 nm.

X-Ray Calc 3: improved software for simulation and inverse problem solving for X-ray reflectivity

This work introduces X-Ray Calc (XRC), an open-source software package designed to simulate X-ray reflectivity (XRR) and address the inverse problem of reconstructing film structures on the basis of measured XRR curves. XRC features a user-friendly graphical interface that facilitates interactive simulation and reconstruction. The software employs a recursive approach based on the Fresnel equations to calculate XRR and incorporates specialized tools for modeling periodic multilayer structures. This article presents the latest version of the X-Ray Calc software (XRC3), with notable improvements. These enhancements encompass an automatic fitting capability for XRR curves utilizing a modified flight particle swarm optimization algorithm. A novel cost function was also developed specifically for fitting XRR curves of periodic structures. Furthermore, the overall user experience has been enhanced by developing a new single-window interface.

Investigation of structural and reflective characteristics of short-period Mo/B4C multilayer X-ray mirrors

The results of a study of the structural and reflective characteristics of short-period multilayer X-ray mirrors based on Mo/B4C at wavelengths 1.54 Å, 9.89 Å and 17.59 Å are presented. The period of the samples varied in the range 8-35 Å. The average widths of the interfaces were ∼3.5 and 2.2 Å at one and the other boundaries, with a tendency for weak growth with any decrease in the period. The interlayer roughness was ∼1 Å. The research results indicate promising prospects for the use of multilayer Mo/B4C mirrors for synchrotron applications.

Be/Si/Al multilayer mirrors as the most promising optical elements for spectroscopy and imaging in the spectral region of 17-32 nm

The reflective and structural parameters of Be/Si/Al multilayer mirrors have been studied. The extent of stability of their X-ray optical characteristics has been demonstrated during storage in air for 4 years and during vacuum annealing at temperatures up to 100°C. A high reflectance of 62.5% was obtained, together with a spectral selectivity of λ/Δλ≈59 at a wavelength of 17.14 nm and 34%, with λ/Δλ ≈ 31 at a wavelength of 31.3 nm. It was shown that Si interlayers reduce the interlayer roughness from 0.45 to 0.20 nm.

Depth-resolved oxidational studies of Be/Al periodic multilayers investigated by X-ray photoelectron spectroscopy

The quantification of surface and subsurface oxidation of Be/Al periodic multilayer mirrors due to exposure in the ambient atmosphere was investigated by depth-resolved X-ray photoelectron spectroscopy. The contribution of oxidation was lower for the thicker layer of Al in the periodic structures since the surface was less chemically reactive for the oxidation. This was investigated by finding the depth-resolved slope of the intensity ratio of metal/oxides (Be/BeO_x and Al/AlO_x) by analyzing the chemical shift of Al 1s and Be 1s photoelectrons. Furthermore, a well-resolved doublet chemical shift in the O 1s spectra indicated the formation of BeO_x/AlO_x and BeOH/AlOH oxides. The investigation showed that the subsurface and surface regions were dominated by metal-hydroxide (BeOH/AlOH) and metal-oxide (BeO_x/AlO_x) bonding, respectively, analyzed by the depth-resolved chemical shifts.

A concept of "materials" diffraction and imaging beamline for SKIF: Siberian circular photon source

Over the next decade, the extremely brilliant fourth generation synchrotron radiation sources are set to become a key driving force in materials characterization and technology development. In this study, we present a conceptual design of a versatile "Materia" diffraction and imaging beamline for a low-emittance synchrotron radiation facility. The beamline was optimized for operation with three main principal delivery regimes: parallel collimated beam ∼1 mm beam size, micro-focus regime with ∼10 μm beam spot size on the sample, and nano-focus regime with <100 nm focus. All regimes will operate in the photon energy range of 10-30 keV with the key feature of the beamline being fast switching between them, as well as between the various realizations of diffraction and imaging operation modes while maintaining the target beam position at the sample, and with both spectrally narrow and spectrally broad beams up to the energy band ΔE/E of 5 × 10^-2. The manuscript presents the details of the principal characteristics selected for the insertion device and beamline optics, the materials characterization techniques, including the simulations of thermal load impact on the critical beamline optics components. Significant efforts were made to design the monochromators to mitigate the very high beam power load produced by a superconducting undulator source. The manuscript will be of interest to research groups involved in the design of new synchrotron beamlines.

Influence of Mo interlayers on the microstructure of layers and reflective characteristics of Ru/Be multilayer mirrors

The influence of Mo interlayers on the microstructure of films and boundaries, and the reflective characteristics of Ru/Be multilayer mirrors (MLM) were studied by X-ray reflectometry and diffractometry, and secondary ion mass spectrometry (SIMS). An increase in the reflection coefficients of MLM at a wavelength of 11.4 nm to record values of R = 72.2% and FWHM to Δλ_1/2= 0.38 nm is shown. The effect of interlayers on the structural and reflective characteristics of MLM is explained by the barrier properties of the Mo layers, which prevent the mutual mixing of the Ru and Be layers, which leads to the formation of beryllides and a decrease in the X-ray optical contrast at the boundaries.

Intrinsic roughness and interfaces of Cr/Be multilayers

The structures of Cr/Be multilayer mirror interfaces are investigated using X-ray reflectometry, diffuse X-ray scattering and atomic force microscopy. The combination of these methods makes it possible to separate the contributions of roughness and interlayer diffusion/intermixing for each sample. In the range of period thicknesses of 2.26–0.8 nm, it is found that the growth roughness of the Cr/Be multilayer mirrors does not depend on the period thickness and is ∼0.2 nm. The separation of roughness and diffuseness allows estimation of layer material intermixing and the resulting drop in the optical contrast, which is from 0.85 to 0.17 in comparison with an ideally sharp structure.

Periodic Multilayer for X-ray Spectroscopy in the Li K Range

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.

Reflecting properties of narrowband Si/Al/Sc multilayer mirrors at 58.4 nm

This study considers the reflective characteristics of three-component Si/Al/Sc multilayer mirrors with a MoSi₂ protective cap layer as candidates for telescopes for observation of the solar corona in the He I (λ=58.4nm) spectral line. At 58.4 nm, a peak reflectance of 32% and a spectral width at a half-maximum intensity of Δλ=5.4nm are obtained. The temporal stability of the reflectance at λ=58.4nm for Si/Al/Sc samples with a 6 nm thick MoSi₂ cap layer is investigated during storage in air for 20 months.