We have developed the design and experimentally studied aperiodic and stack broadband Mo/Si mirrors for the purposes of the KORTES project, optimised for uniform reflection in the 17 - 21 nm ...wavelength range. It is shown that stack structures with an insignificant loss in the reflection coefficient are much more preferable from the point of view of manufacturing and certification, which, in turn, makes it possible to correct the deposition process and to reach the calculated parameters of a multilayer mirror in a small number of iterations.
Microstructural investigation of the Mo/Si nanoscale multilayers (MLs) is essential to design high-reflective nanomirrors. Raman spectroscopy showed existence of silicon layer in the amorphous ...structure. Small fraction of the nanocrystalline silicon (nc-Si) phase was found to be embedded in the amorphous silicon (a-Si) matrix. The disorder in a-Si is increased with the decrease in the thickness of silicon layer in the Mo/Si MLs, determined by the increased bond-angle deviation (ΔΘ) of the Si–Si network. The MLs exposed to high-temperature (HT) showed a decrease in the ΔΘ value, which signifies the relaxation of both molecular disorder and residual stress. X-ray diffraction analysis confirmed the polycrystalline bcc phase of Mo and the formation of intermetallic t-Mo5Si3 phase in the interfaces. This phase is more prominent for higher value of β (thickness ratio of high atomic weight (z) layer to ML period d, i.e. β = dMo/d). Intensity of the Mo (110) plane is decreased for the sample annealed at HT, which is directly related to the degree of amorphization and the formation of intermetallic phases. However, HT annealed Mo/Si showed the growth of Mo (220) planes for higher β value of MLs. Current findings revealed that the disorder in the a-Si and microstructure of the Mo and intermetallic phase depend on the annealing temperature and the β value. The analysis of the intermetallic phase is critical for the development of high reflective mirrors.
Display omitted
•Magnetron sputtered deposited highly reflective Mo/Si multilayer nanomirror films.•Investigation of microscopic phase-structure and intermetallic compounds.•Molecular structure of silicon nanolayers and thermal stability of the intermetallic interfaces.
The emission spectra of krypton plasma in the range of 8 - 14 nm upon excitation of a pulsed gas jet by 1.06-mm Nd : YAG laser radiation with a pulse energy of 0.85 J, pulse duration of 5.2 ns, and ...repetition rate of 10 Hz are investigated. The krypton emission spectrum is a wide (8 - 14 nm) band, peaking at 10.3 nm, which is formed by a series of much narrower lines. The observed lines are identified, and the fraction of laser pulse energy converted into the (8 - 14)-nm emission band and emitted into half-space (2π sr) is determined. The maximum conversion efficiency is found to be 21 %. The expected throughputs of lithographic systems with sources based on Sn, Xe, and Kr ions for different wavelengths, corresponding to the emission peaks of ions of these materials, are compared.
The results of an investigation on oxidation processes in Mo/Be multilayer nanofilms are presented. The films annealed both in ambient atmosphere and in vacuum. The extreme ultraviolet (EUV) and ...X-ray reflectivity of the samples at 11.34 and at 0.154 nm respectively were measured before and after the treatment. No noticeable changes in film thicknesses and boundaries were observed during the annealing at temperatures up to 300°C. An oxidation mechanism of the nanofilms Mo/Be is established and the activation energy of the oxidation process is estimated to be 38 kJ/mol. To determine an absolute quantity of oxygen in the oxidized layers, a simple technique based on the EUV reflectivity data is proposed, and the range of its applicability is subsequently analysed.
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
= 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.
It is shown that the use of traditional multilayer X-ray Pt/C mirrors with a periodic gradient only along the direction of propagation of the central X-ray beam, so-called Goebel mirrors, with a ...source based on the inverse Compton effect, leads to a significant loss of reflected intensity. The efficiency of such mirrors will be about 2% of the total power of the source. To solve this problem, a new approach is proposed based on the use of a set of multilayer mirror strips with different profiles, widths, and periods determined by the parameters of the incident radiation. This work describes the method proposed by us for calculating the period distribution over the mirror surface. The calculation parameters are: the angular dependence of the source photon energy, the mirror size, the distance from the source to the center of the mirror, and the central angle of incidence of radiation on the mirror. The developed method for calculating the periods of a multilayer X-ray mirror is demonstrated by the example of solving a specific problem of X-ray reflection from a source based on the inverse Compton effect, considered earlier in publications. It is noted that in order to apply the technique described in the article when constructing mirrors, it will be necessary to resort to lithography, since obtaining a set of mirrors described in the work using magnetron sputtering seems to be extremely difficult to implement.
The structural inhomogeneities of silicon films embedded within W/Si multilayer mirrors were studied by X‐ray reflection, grazing‐incidence small‐angle X‐ray scattering (GISAXS) and X‐ray ...photoelectron spectroscopy (XPS). In the diffuse scattering spectra, evidence of laterally and vertically ordered in‐layer inhomogeneities was consistently observed. In particular, specific substructures resonant in nature (named here `ridges') were detected. The properties of the ridges were similar to the roughness determined by quasi‐Bragg peaks of scattering, which required a high interlayer correlation of particles. The XPS showed the nanocrystalline nature of the Si particles in the amorphous matrix. The geometric characteristics and in‐layer and inter‐layer correlations of the nanoparticles were determined. In GISAXS imaging, the unusual splitting of the waists between the Bragg sheets into filament structures was observed, whose physical nature cannot yet be explained.
The nature of the observed bulk inhomogeneities in the silicon layers in W/Si multilayers is established. In the diffuse scattering spectra, specific substructures, which are clearly resonant in nature, are observed. The physical nature of some of them is not established.
We describe results of studying emission spectra of Cl-, Br-, and I-containing liquid jet targets in the 3‒6.5 nm wavelength range under their excitation by a pulsed laser. A number of emission lines ...of Cl, Br, and I ions are recorded, including in the “water-window” spectral range of 2.3‒4.4 nm. A specially developed system based on an industrial pulse valve is used for a liquid-jet target to be formed. The targets are excited by an Nd:YAG laser (λ = 1064 nm, τ = 5.2 ns,
E
pulse
= 0.8 J). Using a Bragg spectrometer based on a multilayer X-ray Cr/Sc mirror and Ti/Be absorption filters, absolute intensities of some of the most intense lines are measured. High emissivity of liquid targets is demonstrated; thus, for a bromine-containing target in the 6.12 ± 0.05 nm band, the resulting radiation intensity in the half-space is 1.3 × 10
13
photons per pulse.
Broadband Mo/Si and Mo/Be multilayer stack-type mirrors for wavelength intervals of 11.1–13.8, 17–21, and 28–33 nm have been developed and fabricated. Uniform reflection of such structures can be ...implemented using few corrections of technological process.
We describe a laboratory reflectometer developed at the IPM RAS for precision measurements of spectral and angular dependences of the reflection and transmission coefficients of optical elements in a ...wavelength range of 5-50 nm. The radiation is monochromatised using a high-resolution Czerny-Turner spectrometer with a plane diffraction grating and two spherical collimating mirrors. A toroidal mirror focuses the probe monochromatic beam on a sample. The X-ray source is a highly ionised plasma produced in the interaction of a high-power laser beam with a solid target at an intensity of 1011-1012 W cm-2. To stabilise the emission characteristics, the target executes translatory and rotary motions in such a way that every pulse irradiates a new spot. The short-focus lens is protected from contamination by erosion products with the use of a specially designed electromagnetic system. The samples under study are mounted on a goniometer is accommodated in a dedicated chamber, which provides five degrees of freedom for samples up to 500 mm in diameter and two degrees of freedom for a detector. The sample mass may range up to 10 kg. The X-ray radiation is recorded with a detector composed of a CsI photocathode and two microchannel plates. A similar detector monitors the probe beam intensity. The spectral reflectometer resolution is equal to 0.030 nm with the use of ruled gratings with a density of 900 lines mm-1 (spectral range: 5-20 nm) and to 0.067 nm for holographic gratings with a density of 400 lines mm-1 (spectral range: 10-50 nm). We analyse the contribution of higher diffraction orders to the probe signal intensity and the ways of taking it into account in the measurements. Examples are given which serve to illustrate the reflectometer application to the study of multilayer mirrors and filters.
PDF
