Yu. A. Vainer

Multilayer X-ray mirrors based on La/B4C and La/B9C

Multilayer X-ray mirrors that are based on La/B4C and La/B9C and intended for the reflection of X-ray radiation in the spectral region near λ = 6.7 nm are prepared and studied. Reflection coefficients at a level of 40–60% are achieved for mirrors with various periods. The difference in the interlayer roughnesses reconstructed from the data measured in the hard and soft X-ray spectral regions is explained using a structural model with an asymmetric permittivity profile in a mirror period. A proximate technique is developed to estimate the permittivity profile in a multilayer-structure period using reflectometry data. The effect of antidiffusion Sn, Cr, and Mo barriers on the reflection coefficient of multilayer La/B4C structures is studied experimentally

Roughness measurement and ion-beam polishing of super-smooth optical surfaces of fused quartz and optical ceramics

The main problems and the approach used by the authors for roughness metrology of super-smooth surfaces designed for diffraction-quality X-ray mirrors are discussed. The limitations of white light interferometry and the adequacy of the method of atomic force microscopy for surface roughness measurements in a wide range of spatial frequencies are shown and the results of the studies of the effect of etching by argon and xenon ions on the surface roughness of fused quartz and optical ceramics, Zerodur, ULE and Sitall, are given. Substrates of fused quartz and ULE with the roughness, satisfying the requirements of diffraction-quality optics intended for working in the spectral range below 10 nm, are made.

Particulars of studying the roughness of substrates for multilayer X-ray optics using small-angle X-ray reflectometry, atomic-force, and interference microscopy

The abilities of standard methods for rough surface investigation are analyzed in case of supersmooth substrates for multilayered X-ray optics. The X-ray specular reflection technique is shown to be the most adequate one. X-ray diffuse scattering and AFM can be applied only in a case of PSD-function calculation and approximation over the entire spectrum range of spatial frequencies.

The evolution of roughness of supersmooth surfaces by ion-beam etching

The behavior of roughness on surfaces of Cr/Sc multilayer structure, crystalline silicon [100], and fused quartz upon ion beam etching in the region of middle and high frequencies of the spatial spectrum (10−2–102 μm−1) is studied. The possibility of keeping surface roughness at level σ ∼ 0.3 nm upon etching by Ar atoms/ions to depths of up to 10 μm is demonstrated.

Evolution of the roughness of amorphous quartz surfaces and Cr/Sc multilayer structures upon exposure to ion-beam etching

The effect of ion-beam etching on surfaces of Cr/Sc multilayer structures and amorphous quartz roughness is studied. The dependence of roughness on the depth of etching, incidence angle, and ion energy is considered. Optimal parameters of etching which provide minimal evolution of surface roughness are presented.

Investigation of supersmooth optical surfaces and multilayer elements using soft X-ray radiation

The aim of this work is application of soft X-ray diffuse scattering for certification of diffractiongrade optical elements and their substrates at a working wavelength. A device is suggested that allows certification under laboratory conditions owing to a dynamic range approaching that of synchrotron radiation sources. Experimental data are compared with data of alternative methods.

Analysis of cross-correlation of interface roughness in multilayer structures with ultrashort periods

The diffusion scattering method is used for studying a series of W/B4C multilayer structures with ultrashort periods (d = 0.8–1.5 nm). A simple theoretical model is described; the model takes into account both the dynamic effects in the interaction of counter-propagating diffuse-scattered waves and the mixing of film materials at the boundaries of the layers. It is shown that multilayer structures with a number of bilayers up to N = 700 and values of periods up to 0.8 nm are multilayer structures, which are well-correlated along the boundaries and exhibit resonance diffuse scattering. For structures with a period d > 1.1 nm, the largest contribution to the imperfection of boundaries comes not from the roughness, but from mixing of the films. The range of minimal periods of multilayer structures, for which the continuity of the films is preserved, is determined. The effect of “smoothing” of the substrate surface is discovered in multilayer structures with intact continuity; this contradicts to a certain extent the assumption concerning complete longitudinal correlation of roughnesses, which forms the basis of the theory.

Applying reactive ionic-beam etching to correcting the shape of X-ray mirrors

A procedure for correcting the shape of cylindrical surfaces by means of reactive ionic-beam etching is presented. The results from an experiment on manufacturing a glass surface as an elliptical cylinder are shown.

Using Ion-beam etching to smooth fused silica surfaces

The roughness of fused silica, silicon, and sapphire substrates from different manufacturers is studied. Features of the substrates for imaging optics in the soft X-ray (SXR) and extreme UV (EUV) ranges are discussed. The first results from smoothing quartz substrates by etching with neutralized 50–500-eV argon beams are reported. Surface smoothing has been observed in the spatial-frequency range of 10-1-10-2 μm-1.

Polished sitall substrates for X-ray optics

The parameters of the surface roughness of polished sitall substrates fabricated using a technique developed by the authors are reported. A comparison with the world analog, namely the Zerodur optical ceramic manufactured by Edmund Industrial Optics is performed. The effect of ion-beam etching on the surface roughness for both materials is studied.