To reduce optical losses due to scattering of radiation by crystals in Ga20Ge20Se60 glass-ceramics, selective doping of the glass matrix with lanthanum(III) selenide is proposed. Samples of the (100-x)Ga20Ge20Se60-xLa40Se60 (x = 0, 0.25, 0.625, 1.25, 2.5, 3.75, 5) glass- ceramics, which contain 40-57 vol.% of 3.0-4.6 mu m sized sphalerite-type crystalline phases based on solid solutions of germanium(II, IV) selenides and gallium(III) selenide, are prepared. According to energy-dispersive spectroscopy data, lanthanum is concentrated in the glass matrix of glass- ceramics, and the distribution coefficient is 3.4 +/- 0.6. An increase in the concentration of La in (100-x) Ga10Ge30Se60-xLa40Se60 (x = 0, 1.25, 2.5) glasses leads to the rise of their refractive index by 0.023 +/- 0.008, when replacing 0.25Ga + 0.75Ge -> 1La. For the first time, 97.5Ga20Ge20Se60-2.5La40Se60 selenide glass- ceramics with a high volume content of micron-sized crystals and transparency of more than 50% in the 2-16 mu m region are produced.

We consider a mathematical model of a planar Mach–Zehnder interferometer with nonideal beam splitters. For this model, we obtain two fidelity estimates of the matrix–vector multiplication in the form of dependences of the multiplication error on the beam splitting error in directional couplers. The first estimate is obtained as a measure of the difference between the transfer matrices implemented by interferometers and is presented in the form of the norm of the difference between two unitary matrices corresponding to ideal and non-ideal interferometers. The second estimate is obtained as a measure of the difference in output intensities. It is shown that in the latter case the fidelity depends both on the beam splitter error and on the parameters of the input signals. We verified the second estimate using computer simulations of MZI in COMSOL Multiphysics.

Using a comprehensive approach that includes structural, optical, and theoretical studies, this work offers research demonstrating the capability to evaluate the individual and total effect of strain and segregation on the spectral characteristics of quantum well structures. The samples under investigation contain double asymmetric tunnel-coupled quantum wells based on solid solutions of indium, gallium and aluminum arsenides. The photoluminescence spectra of the structures were observed experimentally at two measurement temperatures, namely 77 K and 300 K. Since the photoluminescence peaks are very sensitive to the quantum well profile, the photoluminescence emitting regions of the grown structures can differ in energy by up to 50 meV due to the design diversity. In turn the elastic strain and compositional segregation effects can lead to the energy shift of the photoluminescence peaks about such order, hence it is important to choose a technique to identify these contributions. Control measurements of the indium content and elastic strains were carried out by means of transmission electron microscopy, namely, by the coordinated application of characteristic electron energy loss spectroscopy and the geometric phase method. Theoretically, using the obtained structural data, the strained quantum well potential profile, quantum-size levels, the envelope wave functions and interband transition matrix elements were calculated. The strong agreement between the modelled and experimental spectra validates our theoretical simulation.

In this paper, we propose a method for predicting the refractive index variation in InGaAlAs tunnel-coupled quantum wells under the action of an electric field. Complex of mathematical and experimental studies to optimize the heterosystems design forthe semiconductor modulator construction according to a planar Mach-Zehnder interferometer scheme is demonstrated.

In this paper, we propose a method for predicting the refractive index variation in InGaAlAs tunnel-coupled quantum wells under the action of an electric field. Complex of mathematical and experimental studies to optimize the heterosystems design forthe semiconductor modulator construction according to a planar Mach--Zehnder interferometer scheme is demonstrated. Keywords: Mach--Zehnder modulator, nanoheterostructure, quantum mechanical calculations, refractive index, transmission electron microscopy, photoelectric spectroscopy.

The memristor is a simple two-terminal device that can be realized as a capacitor-like thin film stack demonstrating the effect of resistive switching (resistive memory) due to atomic (defect) reconstruction, when a voltage of a certain polarity and magnitude is applied. The main physicochemical phenomena associated with the diffusion and drift of oxygen ions (vacancies), local processes of formation and reduction-oxidation of conducting channels (filaments) in different metal-oxide materials are considered in this chapter. The conclusions about the filamentary nature of resistive switching are supported by the local electrical characterization of thin oxide films with scanning probe microscopy techniques and multiscale simulation of electroforming and switching by using phenomenological approaches, ab initio, molecular dynamics and kinetic Monte Carlo methods.

Ge-rich Ga-Ge-Sb-Se glasses with relatively high glass transition temperature and low tendency to crystallization are synthesized. Glass composition effect on the optical and thermal properties is discussed. Analysis of structural units shows the increase in the fraction of Ge-Ge homopolar bonds in the glass network, from 16 to 43%, as the germanium and gallium contents are increased in the 26-29 and 1-5 at.%, respectively. For different glass compositions, the refractive index dispersion in the 500-3000 nm wavelength range is characterized with using the model that takes into account absorption. Correlations between structural features of glasses and physical properties are discussed.

The structure and optical properties of thin films of the chalcogenide semiconductor Ge 2 Sb 2 Te 5 , deposited by magnetron sputtering, was studied. A significant change in the topology and optical properties of the films is demonstrated with varying deposition conditions. It is shown that an increase in the deposition time leads to an increase in the surface roughness. Doping with nitrogen during deposition leads to a smoothing of the film surface, and also provides a strong change in the band structure and optical properties.

Resistive switching and adaptive behavior of resistive state in response to electrical stimulation has been studied for the silicon oxide based memristive devices subjected to electroforming in the conditions of current compliance in comparison with the analogous memristive devices after electroforming without any current limitation. The limitation of current and temperature during electroforming affects the parameters of growing conductive filament ensembles and reduction oxidation reactions resulting in a gradual character and a wide dynamic range of resistance change important for neuromorphic applications.

The new alkoxysilane 2,2-bis(trifluoromethyl)-4,4-diethoxy-1-aza-3-oxa-4-silacycloheptane behaves as a bi- or trifunctional compound, depending on the hydrolysis conditions. In case of a deficiency of water, a mixture of cyclosiloxanes with cyclic substituents at silicon atoms is obtained, while in case of an excess of water, a crosslinked polysiloxane with hydroxyl-containing substituents is obtained. On the basis of the compositions 2,2-bis(trifluoromethyl)-4,4-diethoxy-1-aza-3-oxa-4-silacycloheptane and 3-aminopro-pyltriethoxysilane, under mild conditions in the presence of atmospheric moisture, transparent solid polysi-loxane coatings with very low refractive indexes for nonporous polymers are formed.

Новый алкоксисилан 2,2-бис-(трифторметил)-4,4-диэтокси-1-аза-3-окса-4-силациклогептан в зависимости от условий гидролиза проявляет свойства би- или три-функционального соединения. При недостатке воды образуется смесь циклосилоксанов с циклическими заместителями у атомов кремния, при избытке – сшитый полисилоксан с гидроксилсодержащими заместителями. Из композиций на основе соединения 2,2-бис-(трифторметил)-4,4-диэтокси-1-аза-3-окса-4-силациклогептан и 3-аминопропилтриэтоксисилана в мягких условиях под действием влаги воздуха образуются прозрачные твердые полисилоксановые покрытия с очень низкими для непористых полимеров показателями преломления.

We investigate both experimentally and theoretically the role of migration effects in a relaxation of the ensemble of Si crystallites formed in multilayer SiOx/SiO2 nano-periodic structure with annealing. Photoluminescence spectrum of the multilayer ensemble turns out to be strongly redshifted and narrowed related to its position and width expected from the size distribution of the nanocrystals. Based on the concept of “quantum confinement” we have performed a computer experiment on the ensemble relaxation with taking the migration of electrons, holes, and excitons into account for the ensemble having the size distribution and nanocrystals׳ density similar to those in the experimental sample. This model allows us to calculate the photoluminescence spectrum that agrees well with the one observed experimentally. It was shown experimentally and theoretically that in a dense ensemble, the migration quenches the luminescence of Si nanocrystals whose diameters are, in fact, less than the average nanocrystal diameter in the ensemble. This explains the above mentioned features of the measured spectrum.

The effect of preliminary oxidation annealing of porous silicon (PS) on photoluminescence (PL) under laser pumping at wavelengths of 532 and 980 nm, EPR, and transverse current transport in structures based on PS with a fused tungsten-tellurium glass (TTG) doped with Er and Yb has been studied. It has been shown that such annealing and the presence of silicon nanocrystals (nc-Si) in PS promote multiple PL enhancement for both Er ions in TTG and nc-Si in PS at wavelengths of 750 and 1540 nm, respectively. As TTG is fused into PS, P b -centers of nonradiative recombination are suppressed, while retaining discrete electron tunneling through nc-Si grains in PS.

The results of a numerical simulation of photoluminescence in ensembles of Si nanocrystals incorporated into SiO 2 and ZrO 2 matrices are presented. It is shown that, in the ZrO 2 matrix, which produces a lower potential barrier for electrons and holes in nanocrystals, the photoluminescence intensity decreases significantly and the spectral peak shifts towards lower energies.

It is found that the radiative recombination rate rises when silicon nanocrystals are doped with donors. This rise turns out to be stronger when a nanocrystal surface contains abundant defects capable of capturing electrons emitted by donors.