Multilayer optics for XUV spectral region: technology fabrication and applications

We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography (ψ-13nm) and short period multilayer optics.     

On creating multilayer X-ray focusing mirrors

We review the recent studies and results obtained in the last five years at the Institute for Physics of Microstructures (IPM) in the field of multilayer mirror construction for hard X-ray wavelength range ( 7n = 0.05—0.25 nm), E = 25—5 keV)). Mirrors with cylindrical and spheroidal shapes as well as Kirkpatrick-Baez cross systems are considered.     

Intersectingp — p′ branes inpp-wave background

Several supergravity solutions corresponding to bothDp, as well asDp—Dp′ systems, inNS-NS andR-R pp-wave background originating fromAdS ₃ xS ³ xR ⁴ are presented. The supersymmetry properties of these solutions are analysed along with a brief outline of the world sheet construction for thep — p′ branes.     

Measurements of luminescence decay kinetics using an “Agat” streak-camera in a boxcar mode

Conclusion The specialized measuring setup described in the paper makes it possible to measure correctly and with reasonably high accuracy the luminescence decay kinetics of dyes within the time range from 40 psec to 5 nsec upon excitation in the visible range and at 1.064 μm. The system is highly flexible, having at the same time reasonably large data storage memory, and is completely automated. Such a system, undoubtedly, will be helpful for researchers working in the field of physics of laser media and dyes—passive modulators for femtosecond laser systems. The authors are grateful to M. V. Bondar for fruitful discussions and for help with the experiments. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 1, pp. 128–134, January–February, 1995.     

Study for dual-function EUV multilayer mirror

Studying the distribution of He⁺ in Earth's plasmasphere by detecting its resonantly scattered emission at 304 Å will record the structure and dynamics of the cold plasma in Earth's plasmasphere on a global scale. EUV imaging systems usually utilizes near-normal incidence optics including multilayer mirror and filter. In this paper, the space condition of the Earth's plasmasphere to confirm the expected performance of mirror were analyzed. In order to achieve higher response at 304 Å and reduce 584 Å radiation for the optical system, a new multilayer coating of Mo/Si with UO₂ was developed. Based on optical constants of Mo, Si and UO₂, we used a simplest method to compute the reflectance of this new multilayer mirror range from 100 to 584 Å. The results show the desirable thickness of UO₂ is 17 Å, and the multilayer mirror has a high reflectance of 26.10% at 304 Å and a low reflectance of 0.52% at 584 Å.     

A method for resolving individual bands in absorption spectra

A new algorithm for resolving individual bands in absorption spectra is developed. It is assumed that the spectrum consists of absorption bands with halfwidths determined by different kinds of interactions—specific and nonspecific. The method has good accuracy in the case of the strong overlap of bands (the ratio of the distance between maxima of the peaks to the halfwidth is less than 0.2) and a high computational efficiency. Arkhangelsk State Technical University, 17, Naberezhnaya Severnoi Dviny, Arkhangelsk, 163007, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 400–404, May–June, 1997.     

Figure Error Correction by Reflection Wavefront Control of Cu K<Subscript>α</Subscript> Grazing Incidence Multilayer Mirrors

Reflection phase and amplitude of grazing incidence multilayer mirrors for CuK_α radiation have been studied theoretically to evaluate phase correction effects of multilayer surface milling, which revealed good possibilities of correcting mirror substrate figure errors for focusing and imaging application. The mirror multilayers composed of base materials of Cu and Ni were studied in combination with Al, Be, C, Mg and Si for high reflectivity at a grazing angle of 3° incidence. The theoretical surface milling of Cu/Al multilayers of a period thickness of 1.478 nm provides phase correction of 1.7° per period, which corresponds to an accurate correction of substrate figure errors at a rate of 0.007 nm per period. Thus, the milling after the multilayer fabrication, compared to the milling before the multilayer fabrication, enables far more accurate phase correction with 200 times finer control.     

Design and performance of two-channel EUV multilayer mirrors with enhanced spectral selectivity

In this paper, we present a study on two-channel multilayer mirrors which can operate at two wavelengths in Extreme Ultraviolet (EUV) spectral range. We propose a new method to design two-channel EUV multilayer mirrors with enhanced spectral selectivity. The mirror structure is a stack of two periodic multilayers separated by a buffer layer. We have defined the main parameters which allow adjustment of the distance between different order Bragg’s peak and of wavelength positions of reflectivity minima. Two mirrors have been designed and deposited for solar EUV telescope applications by using this method. The first mirror reflects Fe IX–X line (17.1 nm) and Fe XVI (33.5 nm) lines with attenuation of the He II line (30.4 nm). The second mirror reflects Fe IX–X and He II lines with attenuation of Fe XV (28.4 nm) and Fe XVI lines. Measurements with synchrotron radiation source confirm that, in both cases, for these mirrors, we are able to adjust reflectivity maxima (Bragg peak position) and minima. Such multilayers offer new possibilities for compact design of multi-wavelength EUV telescopes and/or for high spectral selectivity.     

Express interferometry of dense plasma

An express method of diagnostics of a wide class of plasma objects (including dense plasma) with high spectral and spatial resolution is suggested, which allows measurement of spectral line widths comparable with the free spectral interval of a Fabry—Perot interferometer. The proposed method is characterized by sufficient accuracy even with considerable broadening of spectral lines. Kiev T. Shevchenko University, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No.6, pp. 813–817, November–December, 1997.     

SU(N) supersymmetry onS 3 × R spacetime

As the whole physical community is celebrating 30 years of supersymmetry, the aim of the present paper is to analyse an 50(3,1) ×SU(N)— gauge invariant supersymmetric model on the Einstein’s universe. Thus, by exploiting the maximalS ³ symmetry, which allows the use of group theoretical techniques, we deal with a (1/2, 1, 3/2)—spin particle system on theS ³ ×R manifold. After we derive the Dirac-Rarita-Schwinger-Yang-Mills-type field equations, we focus on the additional terms that come into theory as a result of the compactness of space and spin coupling to gravity.     

Exciton transitions in photoluminescence spectra of AIAs/GaAs superlattices

Conclusions The studies performed here have shown that the superlattice samples studied exhibit photoluminescence spectra which agree with the Kronig-Penney model, although in calculating the energies of the radiative transitions it is necessary to take into account the binding energy of the excitons,E _B. Due to the exciton—phonon interaction, the 1HH peak breaks up on the long wavelength side into a Poisson distribution. The energy of the LO phonon so determined is 34 meV. Bands due toD ⁰-A ⁰ andD ⁰X transitions, caused by remaining low-level impurities in the GaAs crystals are also observed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 61, Nos. 3–4, pp. 241–245, September–October, 1994.     

The quantum-chemical modeling of the reaction of nitroso oxides with olefins

The density functional theory method was used to localize minima on the singlet potential energy surfaces of the nitroso oxide—ethylene, phenylnitroso oxide—tetramethylethylene, phenylnitroso oxide—hexene-1, and phenylnitroso oxide-styrene systems and on the triplet potential energy surfaces of the nitroso oxide—ethylene and phenylnitroso oxide-hexene-1 systems. The energetically favorable path was found to be that of (3 + 2) cycloaddition with the formation of five-membered rings, which decomposed into nitrone and carbonyl compound with the simultaneous dissociation of the C-C and C-O bonds. The influence of cis-trans isomerism of nitroso oxides on their reactivity with respect to olefins was studied.     

New design of interference band-pass infrared filter

The new design of the interference band-pass infrared filters is proposed. The analytic expressions for the analysis structure “layer with the high refractive index — interference mirror — layer with the high refractive index” are obtained. The refractive indices optimal and thicknesses of individual layers that limited interference mirror are obtained.     

Self-assembled quantum dot semiconductor nanostructure modeling

The calculation of the electronic structure of a vertical multifold stack of self-assembled InAs/GaAs lens-shaped quantum dots is presented. The developed numerical method is based on a rigorous Hamiltonian formulation of an eight-band k.p perturbation accounting for the carrier kinetics and lattice-mismatch strain endured by the islands. The considered implementation is built upon a custom partition of the unit cell. The accompanying validation analysis—consisting of a comprehensive hierarchy of convergence criteria, qualitative, and quantitative test cases—unequivocally shows that the obtained results adhere to the prescribed zero dimensional physics.     

Clusterization of water molecules as deduced from statistical mechanical approach

Using the methods of statistical mechanics we have shown that a homogeneous water network is unstable and spontaneously disintegrates to the nonhomogeneous state (i.e. peculiar clusters), which can be treated as an ordinary state of liquid water. The major peculiarity of the concept is that it separates the paired potential into two independent components—the attractive potential and the repulsive one, which in turn should feature a very different dependence on the distance from the particle (a water molecule in the present case). We choose the interaction potential as a combination of the ionic crystal potential and the vibratory potential associated with the elastic properties of the water system as a whole. The number ℵ of water molecules that enters a cluster is calculated as a function of several parameters, such as the dielectric constant, the mass of a water molecule, the distance between nearest molecules, and the vibrations of nearest molecules in their nodes. The number of H₂O molecules that comprise a cluster is estimated as about ℵ ≈ 900, which agrees with the available experimental data. Presented at the 2nd International Conference “Physics of Liquid Matter: Modern Problems” (September 2003, Kyiv, Ukraine)     

Tailoring the wetting response of silicon surfaces via fs laser structuring

Control over the wettability of solids and manufacturing of functional surfaces with special hydrophobic and self-cleaning properties has aroused great interest because of its significance for a vast range of applications in daily life, industry and agriculture. We report here a simple method for preparing stable superhydrophobic surfaces by irradiating silicon (Si) wafers with femtosecond (fs) laser pulses and subsequently coating them with chloroalkylsilane monolayers. It is possible, by varying the laser pulse fluence on the surface, to achieve control of the wetting properties through a systematic and reproducible variation of roughness at micro- and nano-scale which mimics both the topology of the “model” superhydrophobic surface—the natural lotus leaf—, as well as its wetting response. Water droplets can move along these irradiated superhydrophobic surfaces, under the action of small gravitational forces, and experience subsequent immobilization, induced by surface tension gradients. These results demonstrate the potential of manipulating liquid motion through selective laser patterning.     

Coherence vs. decoherence in (some) problems of condensed matter physics

We present an ‘overview’ of coherence-to-decoherence transition in certain selected problems of condensed matter physics. Our treatment is based on a subsystem-plus-environment approach. All the examples chosen in this paper have one thing in common — the environmental degrees of freedom are taken to be bosonic and their spectral density of excitations is assumed to be ‘ohmic’. The examples are drawn from a variety of phenomena in condensed matter physics involving, for instance, quantum diffusion of hydrogen in metals, Landau diamagnetism and c-axis transport in high T _c superconductors.     

Quantum diffusion

Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan theory is shown.     

The characteristic X-ray spectra of free atoms of metals

The article presents the results of a study of characteristic X-ray spectra of free atoms by means of a new simple technique. A pulsed electron beam was used for evaporation and to create inner-shell vacancies in free atoms of metals. The spectra were obtained with the help of an X-ray monochromator which allowed precise comparison between the free-atoms spectra and corresponding solid-state spectra. The shifts of the peaks were measured and found to be in the range Δλ/λ≈10⁻⁵–10⁻⁴. The K-, L- and M-series spectra were studied. A number of the free-atoms spectra revealed structure which was not resolved in the solid-state spectra and which is of interest for atomic structure calculation applications. This electron beam technique for the investigation of X-ray characteristic spectra of free atoms can be used for the refinement of X-ray wavelength standards.     

q-Deformed nonlinear maps

Motivated by studies onq-deformed physical systems related to quantum group structures, and by the elements of Tsallis statistical mechanics, the concept ofq-deformed nonlinear maps is introduced. As a specific example, aq-deformation procedure is applied to the logistic map. Compared to the canonical logistic map, the resulting family ofq-logistic maps is shown to have a wider spectrum of interesting behaviours, including the co-existence of attractors — a phenomenon rare in one-dimensional maps.