Spectral characterization of EUV radiation emitted from a laser-irradiated gas puff target

A laser-plasma EUV source is described, which is going to be utilized for characterization of EUV optical components and sensoric devices in the wavelength region from 11 to 13 nm. EUV radiation is generated by focusing a Nd:YAG laser into a double stream gas puff target. By the use of different target gases, broadband as well as narrow-band EUV radiation can be obtained. The emission characteristics of the radiation is monitored by the help of different diagnostic tools including a pinhole camera, an EUV spectrometer, and various EUV photodiodes, either directly or after reflection from multilayer mirrors. Theoretical calculations of collision-induced energy transfer are given in order to explain the observed high degree of electronic excitation in the utilized target gases.     

Nonlinear convective flows in multilayer fluid system

The nonlinear thermocapillary and buoyant-thermocapillary flows in a three-layer system, filling a closed cavity and subjected to a temperature gradient directed along the interfaces, are investigated. The nonlinear simulations of convective regimes are performed by the finite-difference method. The process of transition of unicell structures into multicell structures is studied.     

Low-temperature, solution processing of TiO2 thin films and fabrication of multilayer dielectric optical elements

High-quality TiO₂ thin films have been deposited from aqueous titanium-peroxo solutions via spin coating. The effects of precursor solution pH on the crystallization behavior, morphology, density, and refractive index of the films are reported. From X-ray diffraction measurements, the amorphous as-deposited films are found to crystallize in the anatase phase at 250 °C. Surface and cross-section SEM images reveal that films deposited from an acidic precursor are more uniform and denser than those deposited from a basic precursor. X-ray reflectivity measurements show that films with smooth surfaces and high densities (up to 87% of single-crystal anatase) can be produced at temperatures as low as 300 °C. Measured densities are consistent with high refractive indices at 633 nm of 2.24 and 2.11 for films derived from acidic and basic precursors, respectively. The uniformity and dense nature of the films have allowed fabrication of multilayer dielectric optical elements with thermal processing at only 300 °C. The distributed Bragg reflector with four bilayers exhibits a reflectance of 92% and a stop band width of 150 nm. The optical microcavity has a quality factor of 20. The optical properties of all elements agree well with theoretical models, indicating good optical quality. Use of the precursor chemistry for direct photopatterning of TiO₂ films without a polymer resist is also demonstrated.     

Biodegradation of three-layer laminate films based on gelatin under indoor soil conditions

Three-layer gelatin films, composed of sodium montmorillonite (MMt) - plasticized gelatin (Ge-5MMt) (inner layer) and dialdehyde starch (DAS) - cross-linked and plasticized gelatin films (Ge-10DAS) (outer layers), obtained by heat-compression molding, were submitted to degradation under indoor soil burial conditions for 14 days. Biodegradation of multilayer film as well as individual components and control gelatin films was evaluated by monitoring water absorption and weight loss. It was established that technological treatments performed on gelatin, such as cross-linking, compounding with clay and heat-compression molding have a major impact on the biodegradation rate and extent. The possible reasons are discussed. Weight loss results revealed that the susceptibility to microbial attack during soil burial varied in the order: Ge-10DAS < multilayer < Ge-5MMt < gelatin control film. The intermediate behaviour of the multilayer was associated with the presence of hydrogen-bonding interactions between layers, induced by processing. Scanning electron microscopy revealed that the multilayer was preferentially biodegraded by filamentous microorganisms and even larvae in the later stages of the process. The presence of holes and pits on the multilayer surface was more likely attributed to the preferential removal of glycerol and DAS as shown by thermogravimetric analysis.     

Fabrication of self-assembled ultrathin photochromic films containing mixed-addenda polyoxometalates H5[PMo10V2O40] and 1,10-decanediamine

A layered phosphovanadomolybdate/1,10-decanediamine (1,10-DAD) self-assembled ultrathin film was fabricated by means of alternating adsorption of mixed-addenda polyoxometalates (POMs) (phosphovanadomolybdate, H₅[PMo₁₀V₂O₄₀]) and 1,10-DAD, and its photochromic properties were investigated. It is found that the self-assembled multilayer (SAM) film shows high-photochromic response, excellent photochromic stability and reversibility. The photochromic behavior of the SAM is closely related to the reduction potentials of addenda atoms in mixed-addenda POMs. In the case of photo-reduced mixed-addenda POMs, the electron is localized on the more reducible atom, and the addenda atoms with higher reduction potentials show prior photochromism compared with those with lower reduction potentials. The coloration speed is improved after introduction of V into molybdenum POM. The well-ordered lamellar structure of the film was well maintained during the coloration.     

Possibilities and limitations of synchrotron X-ray powder diffraction with double crystal and double multilayer monochromators for microscopic speciation studies

The performance of a combined microbeam X-ray fluorescence/X-ray powder diffraction (XRF/XRPD) measurement station at Hamburger Synchrotronstrahlungslabor (HASYLAB) Beamline L is discussed in comparison to that at European Synchrotron Radiation Facility (ESRF) ID18F/ID22. The angular resolution in the X-ray diffractograms is documented when different combinations of X-ray source, optics and X-ray diffraction detectors are employed. Typical angular resolution values in the range 0.3–0.5° are obtained at the bending magnet source when a ‘pink’ beam form of excitation is employed. A similar setup at European Synchrotron Radiation Facility beamlines ID18F and ID22 allows to reach angular resolution values of 0.1–0.15°. In order to document the possibilities and limitations for speciation of metals in environmental materials by means of Hamburger Synchrotronstrahlungslabor Beamline L X-ray fluorescence/X-ray powder diffraction setup, two case studies are discussed, one involved in the identification of the crystal phases in which heavy metals such as chromium, iron, barium and lead are present in polluted soils of an industrial site (Val Basento, Italy) and another involved in the speciation of uranium in depleted uranium particles (Ceja Mountains, Kosovo). In the former case, the angular resolution is sufficient to allow identification of most crystalline phases present while in the latter case, it is necessary to dispose of an angular resolution of ca. 0.2° to distinguish between different forms of oxidized uranium.     

多层光变防伪膜的非均匀垂直偏振光反射特性

基于非均匀光波在导电介质中传播时其相移传播方向和振幅衰减方向的不一致性,利用光波动方程的解由电磁场边界条件导出非均匀垂直偏振光在多层超薄金属膜与透明介质膜组合膜系中光波的传输递推公式.为验证方法的可靠性,给出了不同厚度金属膜防伪光变膜系的能量反射率算例,并与现有算法进行对比,结果表明:两种算法得到的能量反射曲线的分布特征具有很好的相似性,但本文算法表现出金属膜具有强的吸收特性和窄带反射效应.     

Investigation in the interface roughness of DC-sputtered Mo/B4C multilayer mirrors with variable layer pairs for 7-nm soft X-ray polarizers

The surface and interface roughness of Mo/B₄C multilayer mirrors for 7-nm soft X-ray polarizer with variable layer pairs (N = 50, 70, 90 and 110), fabricated by DC sputtering technique is investigated by atomic force microscopy and X-ray scattering and reflecting. The experimental results present that the surface and interface roughness of Mo/B₄C multilayer mirrors increase layer by layer from its substrate as its Mo layer thickness greater than 2 nm, and the roughness grown tendency could be characterized by a quadratic function.     

Temporal diffraction characteristics of transmitted multilayer volume holographic grating illuminated by an ultrashort pulse

Based on the coupled wave theory of Kogelnik and Fourier optics, the time-domain diffraction characteristics of tramsmitted multilayer volume holographic grating (MVHG) under an ultrashort pulse readout are investigated. It is shown that the temporal diffraction characteristics depend not only on the numbers of the grating layers, but also on the thicknesses of the grating layers and buffer layers, grating period and the refractive index modulation. Furthermore, using group velocity dispersion we give explanation on the time-delay of diffraction pulse with respect to the center of the readout pulse. Results of our discussion may find applications in optical communications, pulse shaping and processing.     

Geometry-induced electron doping in periodic semiconductor nanostructures

Recently, new quantum features have been observed and studied in the area of nanostructured layers. Nanograting on the surface of the thin layer imposes additional boundary conditions on the electron wave function and induces G-doping or geometry doping. G-doping is equivalent to donor doping from the point of view of the increase in electron concentration n. However, there are no ionized impurities. This preserves charge carrier scattering to the intrinsic semiconductor level and increases carrier mobility with respect to the donor-doped layer. G-doping involves electron confinement to the nanograting layer. Here, we investigate the system of multiple nanograting layers forming a series of hetero- or homojunctions. The system includes main and barrier layers. In the case of heterojunctions, both types of layers were G-doped. In the case of homojunctions, main layers were G-doped and barrier layers were donor-doped. In such systems, the dependence of n on layer geometry and material parameters was analysed. Si and GaAs homojunctions and GaAs/AlGaAs, Si/SiGe, GaInP/AlGAs, and InP/InAlAs heterojunctions were studied. G-doping levels of 10¹⁸–10¹⁹ cm⁻³ were obtained in homojunctions and type II heterojunctions. High G-doping levels were attained only when the difference between band gap values was low.