Small-angle X-ray studies of the GaAs0.7Se0.3 solid solution at energies close to as and Se absorption edges

The possibility of a simultaneous use of X-ray diffraction and X-ray absorption techniques in order to characterize the sizes, shapes, and chemical composition of grains in a sample (the solution of the extended uncertainty problem due to the Babinet principle) is shown. A sample of the GaAs_0.7Se_0.3/GaAs solid solution is investigated on the developed laboratory device for a simultaneous performance of X-ray diffraction and X-ray absorption experiments. It is shown that the GaAs_0.7Se_0.3 sample decomposes into separate GaAs and GaSe domains forming a mosaic structure. The sizes of GaAs and GaSe domains are estimated. Components with a linear geometry are sometimes revealed in the composition of GaSe grains.     

X-ray studies of the domain formation in rocks under blasting

Quartz plates placed in concrete are used to model the rock blasting procedure. Quartz fragments resulted from blasting are studied by small-angle X-ray scattering. Obtained grains in the quartz fragments are approximately 200–220 nm in size. The samples are discovered to contain low-dimensional (linear) components; the further the sample is from the explosion center, the coarser the grains are in it. Superlattice parameters of the studied fragments are estimated. It is suggested that domain boundaries in the sample quartz fragments are linear objects, such as dislocation walls.     

Calculation of field in plane-layered microelectronic materials

A modification of the method for calculation of horizontal and vertical components of monochromatic field that is generated in plane-layered medium by horizontal current flow and described using wave equation is proposed for problems of microelectronics. The proposed solution is based on the verified method of equivalent propagation constant that makes it possible to substantially reduce the amount of calculations in comparison with alternative methods based on rigorous dynamic approach. The analysis illustrates the application of the method at relatively small distances.     

Integrated characterization of multilayer periodic systems with nanosized layers as applied to Mo/Si structures

The potential inherent in integrated characterization of multilayer periodic systems employed in development of extreme-ultraviolet mirrors was demonstrated using the example of Mo/Si structures grown by magnetron sputtering in different technological regimes. An integrated study provided mutually consistent data on the thicknesses and crystal structure of the layers, as well as on the quality of the interfaces. Measurements by atomic force microscopy permitted a comparison of surface roughness of the substrates and the multilayer systems grown on them. An analysis of the power spectral density functions revealed that low-frequency roughness is replicated from the substrate, whereas the high-frequency one can become smoothed out in the course of growth. X-ray diffractometry performed in the thin film mode showed that the Mo layers in the samples studied have different crystal structures, from the amorphous and polycrystalline to the [110]-textured one. An analysis of the transmission electron microscopy data confirmed that there is a difference in the degrees of crystallinity of Mo layers. The thicknesses of individual layers, the period, and the irreproducibility of the thicknesses and the period were determined using X-ray reflectometry. The root-mean-square roughness amplitude of the interfaces was estimated, and the existence of transition layers originating primarily from the Si layer was demonstrated. The study was used to formulate a proper strategy for the analysis of multilayer periodic systems with nanosized layers.     

Method for calculating the monochromatic field in a layered medium

An approximate method is proposed for calculating the monochromatic field described by the wave equation in a layered medium. The method is based on the use of the equivalent propagation constant and makes it possible to reduce the computation time as compared to other methods based on the strictly dynamic approach. The range of correct application of the method is estimated for the problems for which the exact solution is known.     

Features of the structure and defect states in hydrogenated polymorphous silicon films

The structural and electronic properties of thin hydrogenated polymorphous silicon films obtained by plasma-enhanced chemical vapor deposition from hydrogen (H₂) and monosilane (SiH₄) gas mixture have been studied by means of transmission electron microscopy, electron paramagnetic resonance (EPR) spectroscopy, and Raman spectroscopy. It has been established that the studied films consist of the amorphous phase containing silicon nanocrystalline inclusions with the average size on the order of 4–5 nm and the volume fraction of 10%. A signal was observed in the hydrogenated polymorphous silicon films during the EPR investigation that is attributed to the electrons trapped in the conduction band tail of microcrystalline silicon. It has been shown that the introduction of a small fraction of nanocrystals into the amorphous silicon films nonadditively changes the electronic properties of the material.     

Domain structure of GaN/SiC-based materials for semiconductor lasers

The domain structure of GaN/SiC hexagonal semiconductor films has been studied using small-angle X-ray scattering in order to determine possible domain configurations in a GaN/SiC film that can influence the properties of the laser on its basis. Data on specific features of the samples, such as geometrical properties of clusters and the distances in superstructures (layers, superlattices), respectively, have been obtained by the processing of the small-angle X-ray scattering spectra according to Porod’s and Bragg’s models. A model of regular network of domain walls in GaN/SiC film has been proposed. The hypothesis on the formation of filamentary structures near the film-substrate interface has been confirmed.     

Mutual synchronization of two coupled self-oscillators based on GaAs/AlGaAs superlattices

The interaction of self-oscillators based on 30-period weakly coupled GaAs/AlGaAs superlattices is studied. The action of one self-oscillator on the other was observed for a constant bias voltage in the absence of generation of self-sustained oscillations in one of the oscillators. It is shown that induced oscillations in a forced oscillator appear due to excitation of oscillations in the system of coupled oscillators forming the electric-field domain wall at the frequency of one of the higher harmonics of a forcing oscillation.     

Study of Thin Films of High Temperature Superconductors Based on YBaCuO by EPMA

 An analytical model of an effective atomic number, Z _eff, for simultaneous calculation of composition and thickness of films on substrates that allows for backscattering processes is presented. Comparison of dependencies of ϕ(ρz) parameters for film elements on electron beam energy, on atomic numbers of a film and a substrate and on film thickness was done. The errors inherent in EPMA have been determined by comparing experimental data obtained on YBa₂Cu₃O_7−x bulk crystals with model calculations. Possibility of EPMA as an effective technique for investigation of spatially inhomogeneous objects was demonstrated by studying the correlation between composition and local superconducting properties (values of critical temperature and critical current) of these films.