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Elastically strained supermultiperiod (100–1000 periods) AlGaAs/GaAs superlattices with different doping levels and slightly differing period thicknesses have been investigated. The proposed technique of characterization consisting of combined application of deep X-ray reflectometry based on a rigorous calculation method, as well as the well-known method of high-resolution X-ray reflectometry, has made it possible to investigate 100-period structures with 2-nm-wide Al0.3Ga0.7As barriers and 10-nm-wide GaAs wells and determine with a high accuracy the layer thicknesses and spread of interfaces. This achievement can be considered as a first step in further analysis of thick structures using bright synchrotron radiation source. The difference between the expected and obtained by the proposed method layer thicknesses is several percent, including that for samples with a high doping level (up to 1018 cm–3). All supermultiperiod structures are characterized by sharp interfaces with a standard deviation of about 0.1 nm. Based on the obtained data on the thicknesses, one can accurately determine the layer compositions using high-resolution X-ray diffraction. [ABSTRACT FROM AUTHOR]

High-frequency multilayer-coated blazed diffraction gratings (HFMBGs) are most promising elements for ultrahigh resolution soft x-ray spectroscopy. As it has been demonstrated recently [Voronov et al., Opt. Express 23, 4771 (2015)], the efficiency limit for in-plane diffraction can exceed 2-3 times, in higher orders too, when the period of a HFMBG is shorter than an attenuation length for soft x-rays and a bilayer asymmetry is designed. In this letter, using numerical experiments based on the rigorous electromagnetic theory, a possibility of off-plane diffraction and symmetrical multilayer coatings to enhance the efficiency of soft-x-ray high-order HFMBGs very closely to the absolute limit, i.e., 0.92-0.98 of the reflectance of the respective W/B4C multilayer, has been demonstrated. [ABSTRACT FROM AUTHOR]

Diffraction from 1D multilayer gratings having arbitrary border profiles including edges is considered for small wavelength-to-period (λ/d) ratios, the most difficult case for any rigorous numerical method. The boundary integral equation theory is so flexible that we can indicate a few areas where it can be modified. In this work, special attention is paid to the main aspects of the Modified Boundary Integral Equation Method for λ/d << 1 as well as to a more general treatment of the energy conservation law applicable to multilayer absorption gratings. Three types of small λ/d problems are known from optical applications: (a) shallow gratings working in the X-ray and extreme ultraviolet ranges, both at near-normal and grazing angles, (b) deep echelle gratings with a steep working facet illuminated along its normal by light of any wavelength, and (c) rough mirrors and gratings in which rough boundaries can be represented by a large-d grating, and which contain a number of random asperities illuminated at any angle and wavelength. Numerical examples of diverse in-plane diffraction problems are presented. [ABSTRACT FROM AUTHOR]

High-resolution grazing X-ray reflectometry is used to obtain experimental and theoretical data on the intensity of specular and diffuse reflection from self-organized structures grown by molecular beam epitaxy with single-layer (non-overgrown) and multilayer (overgrown) Ge/Si quantum dots (QDs). Using the positions of diffuse scattering peaks in the direct space, the slopes of quasi-periodic faces have been determined to within ±0.1° by a method employed previously for the investigation of In(Ga)As/GaAs quantum dots. Finding the quasi-periodic {11 n} ( n = 7−11) faces (typical of the growth of ordered QDs) in the samples with disordered Ge/Si quantum dots is evidence of the generality of mechanisms of QD formation in different systems. [ABSTRACT FROM AUTHOR]