The evolution of silicon surface roughness is studied under scanning ion beam etching for high precision manufacture applications. The experiment is carried out using an 800 eV Ar ion beam generated through metal mask and different etching depths from 240 nm to 1330 nm was carried out. The processed surface is characterized via atomic force microscope, grazing incidence X-ray reflectivity, and X-ray fluorescence spectroscopy, to study the surface morphology, optical contrast and composition changes. It is found that the processed surface is smoothed from 0.14 nm to 0.10 nm (Root mean square) in the initial stage of etching, while further etching (deeper than similar to 1 mu m) would cause growth of nanodots structure with increased roughness. Contaminants sputtered from the ion beam mask and sample holder are detected on the processed surface and the related agglomeration and micro-masking effects of the contaminants are considered as the main mechanism for surface roughening. The roughened surface can be smoothed from 0.41 nm down to 0.10 nm (Root mean square) using the same etching parameters with only similar to 10 nm etching depth after exposure to air. The results show that the surface smoothing or roughening mechanism of Si can be closely related to the surface composition and structure, which provide useful guidance for the manufacture of high precision and ultrasmooth optics.

The internal layer structure and optical performance of B4C coating for X-ray free-electron laser (XFEL) applications were studied. Surface morphology analysis shows that the B4C layer growth at 5 mTorr replicates the substrate morphology at low and mid frequencies but adds slight high-frequency roughness, with the RMS value increasing from 0.13 to 0.33 nm. To investigate the internal physical and chemical structure of B4C, angle-resolved X-ray photoelectron spectroscopy (ARXPS) and depth profiling were performed. Together with soft X-ray (SXR) and hard X-ray (HXR) reflectivity measurements and the fitted results, a three-sublayer model with different composition and density was built for the 50 nm B4C coating. The developed B4C coating was further deposited on a 600 mm length mirror with a thickness variation of 0.7 nm (peak-to-valley). The radius of curvature changed slightly from 181 km before coating to 128 km after coating, and the slope errors were maintained at around 0.07 µrad, indicating a high-performance and large-size B4C coating for the XFEL.

Resonant inelastic X-ray scattering (RIXS) is a photon-in/photon-out spectroscopic technique which has become increasingly important for the condensed matter physics community. The development of the RIXS instrumentation in soft X-ray and hard X-ray range facilitated the research in 3d and 5d transition metal (TM)-based materials, respectively. However, the tender X-ray (2000–3000 eV) RIXS covering most of 4d TM-based materials severely falls behind due to the lack of high-performance energy dispersive optics. Here, we demonstrate the design and fabrication of a laterally graded multilayer grating (MLG) optics for the establishment of the tender RIXS at the I21 RIXS beamline in Diamond Light Source. The successful implementation of the MLG boosts the photon flux by more than an order of magnitude at the Sulfur K-edge (2475 eV) and the Ru L3-edge (2838 eV) in comparison to the solution of a single-layer coated grating (SLG). More importantly, MLG retains the high energy resolution of the SLG design (~10,000) and works continuously across the full range of 2000–3000 eV. It renders the I21 beamline as the very first RIXS facility in the world that covers both soft and tender X-rays (280–3000 eV) using a grating-based spectrometer for a wide range of science applications. Multilayer-grating-based spectrometer with high photon flux and moderate energy resolution for tender X-ray

The internal layer structure and optical performance of B 4 C coating for X-ray free-electron laser (XFEL) applications were studied. Surface morphology analysis shows that the B 4 C layer growth at 5 mTorr replicates the substrate morphology at low and mid frequencies but adds slight high-frequency roughness, with the RMS value increasing from 0.13 to 0.33 nm. To investigate the internal physical and chemical structure of B 4 C, angle-resolved X-ray photoelectron spectroscopy (ARXPS) and depth profiling were performed. Together with soft X-ray (SXR) and hard X-ray (HXR) reflectivity measurements and the fitted results, a three-sublayer model with different composition and density was built for the 50 nm B 4 C coating. The developed B 4 C coating was further deposited on a 600 mm length mirror with a thickness variation of 0.7 nm (peak-to-valley). The radius of curvature changed slightly from 181 km before coating to 128 km after coating, and the slope errors were maintained at around 0.07 µrad, indicating a high-performance and large-size B 4 C coating for the XFEL.

What we believe to be a novel approach is proposed and theoretically justified to achieve the extremely high spectral purity and high diffraction efficiency of a wideband multilayer-coated blazed grating (BMG) in the tender X-ray range (2.5-3 keV photon energy). The key feature consists of depositing a 70 nm thick B4C film on the BMG surface with subsequent removal of the saw-tooth relief by polishing. Such a design allows suppressing the low-energy parasitic radiation intensity by a factor exceeding 104 on the grating surface through reflection from the film in the total external reflection conditions. A high diffraction efficiency of 8-21% for the -2nd order can be achieved at the same time.

A high-precision and efficient method is developed to correct the two-dimensional (2D) surface topography of X-ray mirrors using an elliptical beam spot and a single-axis ion beam figuring (IBF) system. Compared with conventional circular beam spots, the smaller tangential size of the elliptical beam spot enables a higher cut-off frequency and improved figuring correction precision in the tangential direction. The larger sagittal size reduces the number of scanning lines and the figuring time required to complete a relatively wide X-ray mirror. As a first demonstration, elliptical Gaussian-shaped beam spots are generated using specially designed elliptical holes and a broad ion beam source. A mirror with 380 mm × 40 mm optical surface clear aperture is figured using the proposed method. After fast correction using a large circular beam function of σ = 10 mm and fine correction using an elliptical beam function of σtan = 2 mm/σsag = 5 mm, the 2D height error is significantly reduced from 14.5 nm to 1.2 nm (root mean square error). The tangential slope error reaches 384 nrad, which can be further improved. The IBF method with a non-spherical spot can be applied to the manufacturing of many other mirrors that have different requirements in two dimensions with high convergence efficiency.

Grating optics lie in the heart of X-ray spectroscopy instruments. The low efficiency and angular dispersion of conventional single-layer-coated gratings significantly limit the transmission and energy resolution of monochromators and spectrometers, particularly in the tender X-ray region (E = 1-5 keV). Multilayer-coated blazed gratings (MLBGs) operating at high diffraction orders offer the advantage of achieving both high efficiency and high dispersion simultaneously. Tender X-ray monochromators and spectrometers using different high-order MLBGs have been designed, all demonstrating one to two orders of magnitude higher transmission compared to conventional systems. By employing a 2400 l/mm MLBG at the -4th or -8th diffraction order, the theoretical energy resolution of the instrument is improved by two to three times at 2.5 keV. Two MLBGs operating at the -2nd and -4th orders have been fabricated, showcasing remarkable efficiencies of 34%-12% at 2.5 keV, surpassing that of single-layer-coated gratings by an order of magnitude. Further optimization of manufacturing accuracy can yield even higher efficiencies. The measured angular dispersion agrees well with theoretical predictions, supporting the potential for high resolution. High-order MLBG optics pave the way for a new generation of tender X-ray monochromators/spectrometers that offer both high transmission and high resolution. (c) 2025 Chinese Laser Press

Al/Sc multilayers are potential optical elements to be used for the extreme ultraviolet range at wavelengths longer than the Sc M2,3 absorption edge. The existing research exhibits a significant gap concerning the incorporation of a barrier layer within the Al/Sc multilayer to enhance interface quality. A series of Al/Sc, Al/Sc/Mo, Al/Mo/Sc, and Al/Mo/Sc/Mo multilayers were fabricated by the direct-current magnetron sputtering technique. Grazing incidence X-ray reflectivity, transmission electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray absorption spectroscopy were used to investigate the effect of Mo barrier layers on interface properties and layer microstructure of Al/Sc multilayers. The results indicate that Mo barrier layers with a thickness of approximately 0.5 nm at different interfaces perform different functions. The Mo barriers at Al-on-Sc interfaces primarily play a role in suppressing the columnar crystallization of Al layers, contributing to the smoothening of interfacial roughness. The thin Mo layers at Sc-on-Al interfaces mainly act as antidiffusion barriers, preventing the diffusion of Al atoms into Sc layers. A model of the impact of Mo barrier layers on the interface diffusion and microstructure of Al/Sc multilayers has been established.

Multilayer coated toroidal mirrors have been widely used in X-ray optical systems to focus/collimate the X-ray beams. The variation of grazing incidence angles at different positions in the tangential direction of the toroidal mirror necessitates a lateral gradient of the multilayer d-spacing. Additionally, a small radius of curvature (RoC) in the sagittal direction and the compact size of the mirror make the deposition more difficult. Here, a toroidal mirror with a 10×10mm2 effective area and an 18 mm sagittal RoC was coated with a W/Si multilayer with high precision. The multilayer d-spacing was changed from 3.48 to 4.18 nm along the tangential direction and kept constant along the sagittal direction, using both varied motion speeds of the substrate and a mask. The experimental deviation of the d-spacing with the designed value was less than ±1%. The interface quality of the multilayer at different positions of such a strongly curved mirror remains the same, and the measured X-ray reflectivities are all between 65% and 68% at 8 keV.

The time-resolved backlight imaging of plasma is crucial for diagnosing densitydependent plasma information. It requires a high-intensity X-ray source and efficient optics. We propose a quasi-coaxial, multi-channel Kirkpatrick-Baez (KB) structure that realizes highbrightness illumination. The angles between the observation axes of neighboring images were significantly reduced. An X-ray multilayer was optimized to enable the system to simultaneously function at two quasi-monochromatic energies to observe the plasma regions of varying densities. Eight-frame high-spatiotemporal-resolution images were obtained with an X-ray backlighter in ShenGuang-III prototype laser facility. This study reports the optical design, multilayer fabrication, and experiments of the proposed microscope.

WC/SiC multilayers are considered as promising optical elements for the application of reflecting hard X-rays efficiently, which allow for very small d-spacings owing to smooth and sharp interfaces. In this paper, to explore the influence of background pressure during fabrication, a set of WC/SiC multilayers with a period thickness of approximately 3 nm were prepared by direct current magnetron sputtering technique under different background pressures. The effect of residual background gases on the interface and surface morphology was investigated by using grazing incidence X-ray reflectivity, X-ray diffuse scattering, optical profiler, and atomic force microscope. High background pressure contributes to increased interface roughness, intensified interface diffusion, reduced lateral correlation length, and diminished vertical correlation. An increased root-mean-square surface roughness in high spatial frequency range is observed in case of high background pressure. The evolution of elemental distribution and chemical state in WC/SiC multilayers induced by varied background pressure was characterized by using X-ray photoelectron spectroscopy. According to the results, a mechanism by which background pressure influences the structural properties of WC/SiC multilayers has been established. Finally, it is concluded that to fabricate WC/SiC multilayers with favorable performance, the background pressure requires not exceeding 2 x 10-4 Pa.

An analytic theory of X-ray (E∼0.04-4 keV) diffraction from wideband multilayer coated gratings is developed. It is found that the wideband blazed gratings can operate in the single-order regime when only one diffraction wave is effectively excited. The diffraction efficiency achieves the reflectivity of conventional depth-graded multilayer mirrors in a wide spectral range. The physical reasons and the conditions of the single-order regime of wideband multilayer grating operation are discussed. A simple and clear design procedure is developed to suppress undesirable diffraction orders. The way to achieve a high diffraction efficiency plateau of 25% throughout the E = 2-3 keV interval is demonstrated.

Mo/Si multilayer mirrors have been widely used in extreme ultraviolet (EUV) astronomy, microscopy, and advanced lithography. To extend the lifetime of Mo/Si multilayer, the protective coating is important for actual application. In this paper, TiO2 and SiO2 have been chosen as the protective coating for Mo/Si multilayers. To investigate the fabrication process of TiO2 and SiO2 by ion beam sputtering (IBS), a comparative study on the choice of sputtering targets has been detailed conducted. Oxide monolayer samples were characterized by grazing incidence X-ray reflectivity (GIXRR), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The Mo/Si multilayer deposited with ultra-thin TiO2 and SiO2 protective coating was analyzed by transmission electron microscope (TEM) and angle-resolved XPS. The results indicated the protective coating has low surface roughness and the dioxide component is higher than 95 %. The reflectivity of Mo/Si multilayer with and without protective coating have been measured at synchrotron radiation facility. The reflectivity drop was similar with theoretically calculation based on the precise thickness control.

The universal approach was originally developed to design wideband multilayer coated blazed gratings operating in the tender X-ray region (E = 2-3 keV), realizing different diffraction geometries including constant incidence angle, constant Cff-factor, and constant deviation angle, while retaining high diffraction efficiency in a wide spectral range.The designed gratings coated by depth-graded Cr/C multilayer structures and operating in the -1st diffraction order are demonstrated to provide the constant factor Cff = 2.52 or the constant deviation angle ψ = 4.75° with the diffraction efficiency of 29% ± 2% or 17.5% ± 1.5%, respectively, throughout the 2-3 keV spectral range.

High-reflectivity Ni/Ti supermirrors, guiders, multi-shell nested and multi-channel focusing systems have been successfully designed and fabricated to achieve the transmission, focusing and collimation of neutron beam using direct-current magnetron sputtering and integrated assembly technology.

A series of La/B4C multilayers with different C-barriers were deposited using magnetron sputtering dedicated for a wavelength ca. 6.7 nm wavelength. Grazing incidence X-ray reflectometry, atomic force microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy were used to investigate the physical structure of the multilayer with different barrier layers. It was found that 0.2 nm carbon barrier at the B4C-on-La interface slightly improved the physical structure especially compared to adding C barrier at the other interface or with larger thickness. In-depth X-ray photoelectron spectroscopy profile measurements indicated an increased formation of C-La bond, which potentially decreased the content of the optically unfavorable B-La bond in the competitive reaction at interfaces. A reduced interlayer density was also found after the deposition of C barrier according to the fitted results of hard X-ray and EUV reflectance. It is estimated that the reduced density and different composition of the interlayer contribute to the enhanced EUV reflectance of the La/B4C/C multilayer. The highest reflectance for the C-barrier sample is 49.4 % at 6.640 nm, while the highest reflectance for the No-barrier sample is 37.6 % at 6.616 nm.

The reference mirror error in an interferometer is a crucial factor affecting the accuracy of x-ray mirror metrology. In this study, a reference surface (RS) reconstruction method based on redundant data from sub-aperture stitching interferometry (SSI) and the attitudes of each sub-aperture is developed to obtain both second- and high-order surface errors. Theoretical simulations show that the errors of the fitted angle attitudes of sub-apertures and the reconstructed reference increase with the second-order term of the surface under test (SUT). Decreasing the second-order term of the SUT to below 2.5 nm (RMS) can improve the accuracy of the fitted sub-aperture attitudes to below 100 nrad and the reconstructed RS to below 1 nm (RMS). This was experimentally demonstrated using mirrors with different second-order terms in SSI measurements and the accuracy of reconstructed references was verified based on different calibration methods. The accuracy of the overall reconstructed RS reached 0.78 nm RMS and the high-order terms reached 0.37 nm.

Neutron supermirror is an important neutron optics component which uses the total reflection principle to transport neutron beams. The formation of interface intermetallics and interface roughness with total multilayer thickness limit the neutron reflectivity performance of Ti/Ni multilayers. The interface roughness of multilayer film was optimized by adjusting the ratio of N2 when sputtering the Ni layers, which ultimately guided the preparation of Ti/Ni neutron supermirrors with improved reflectivity. Direct current reactive magnetron sputtered samples were prepared with different N2 ratios. And the surface morphology was studied by atomic force microscope (AFM), which revealed that 10 % N2 inhibited the roughness growth of film by refining grains. The results of interfacial structure observed by neutron reflectivity were consistent with the AFM, that the average interfacial roughness of the film was minimized at 10 % N2 ratio. The magnetization strength measured by vibrating sample magnetometer was affected by the number of bilayers and the N2 ratio of the magnetic material. Finally, the Ni layers were sputtered with 10 % ratio of N2, which resulted in a 2.7 % reflectivity enhancement compared to m = 2 Ti/Ni supermirror with pure Ar in the q range of 0.03-0.04 & Aring;-1.

Metal mirrors with ultra-smooth surfaces have a wide range of applications in X-ray and other optics. The fabrication of X-ray mirrors usually requires high-precision turning and grinding, which has a periodic texture with anisotropic characteristics. To obtain a stable low roughness surface over the full-aperture surface, it is crucial to study the evolution law of these textures during polishing. In this article, a model for the evolution of periodic texture roughness based on contact mechanics and fluid micro-cutting has been established. It was found that the fluid cutting stress caused by the periodic texture orientation had a significant impact on the evolution of roughness. When the orientation of periodic texture is perpendicular to the rotation direction of polishing wheel, the contribution of fluid micro-cutting to the evolution of the roughness reaches its maximum. The evolution speed of surface roughness is the fastest. Polishing experiments using single direction rotating wheel on turned electroless nickel plate were performed to verify the theory. The experimental results were in good agreement with the theoretical results. This work shows that the fluid micro-cutting plays an important role in the evolution of periodic texture roughness. It provides useful guidance for full-aperture polishing of anisotropic textures.

Stitching interferometry is essential for X-ray mirror metrology where lateral distortion and pixel size are critical factors influencing its accuracy. Simulations and experiments reveal that 1% error in pixel size causes a 2% deviation in the radius of curvature. After correcting pixel size, the stitching profile error of an elliptical mirror reduces from 2 mu m to 250 nm (peak-to-valley). Lateral distortion correction can further reduce retrace errors. For stitching measurements using small sub-apertures, distortion correction can be minor if the average pixel size has been corrected and the actual distortion along the stitching direction is small.