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The article is devoted to the study of light-emitting heterostructures based on GaP(As,N) dilute nitrides, monolithically grown on silicon substrates by plasma-assisted molecular beam epitaxy. Current-voltage characteristics and electroluminescence spectra of the grown heterostructures are obtained. For the first time, a unique effect is observed in GaP(As,N) dilute nitrides - the appearance of white electroluminescence when a reverse bias is applied. The result was obtained due to the original design of the light-emitting heterostructure and the unique properties of dilute nitride solid solutions.

A double slot antenna for X-band applications was designed and aerosol jet printing technology was used to fabricate the prototype with silver nano-ink on a flexible polyimide substrate. We investigated the microwave losses of printed antennas in the range from 100 kHz to 27 GHz, obtained at sintering temperatures of 200 °C and 250 °C. Double slot X-band antennas have been calculated and measured. It was found that an operating bandwidth of the printed antenna is 10% in the region of the central frequency of 10.5 GHz. Thus, the possibility of forming antennas on flexible polymer substrates with high functional characteristics by aerosol jet printing method has been demonstrated.

The article presents the results of studies by the numerical method of pile and slab foundation with a reinforced base by the method of deep soil mixing (DSM) under the influence of seismic loads using the LIRA-SAPR software package, which implements the finite element method. The parameters of the computer model are presented, which make it possible to obtain the calculation results. A comparative analysis of the calculation results is carried out. In the course of the study, it was revealed that the use of a slab foundation with a reinforced base by the deep soil mixing method (DSM) is more effective than a pile foundation under seismic loads.

A new method for nanopit formation by molecular-beam epitaxy (MBE) on different silicon substrates has been investigated. The dependence of the shape and depth of the nanopits on substrate orientation and doping type has been studied. The samples with an array of nanopits with 25 nm depth and (2-6)·108 cm−2 density for subsequent monolithic selective growth of quantum dots (QD) have been created.

Formation and propagation of the antiphase domains in dilute nitride GaPN/GaP epitaxial heterostructures grown on Si (001) by plasma assisted molecular beam epitaxy (PA-MBE) on silicon is studied. Role of the layer composition, substrate orientation and growth conditions are discussed. Composition of the dilute nitride film was studied by X-ray diffraction (XRD) while the effect of the antiphase disorder in GaP buffer layer on GaPN epilayer structural properties was studied by transmission electron (TEM) and scanning electron microscopy (SEM). Controllable transition between antiphase disordered and monodomain film depending on the concentration of incorporated nitrogen is demonstrated – transition to the monodomain film occurs in dilute nitride GaPN layers starting low with 0.4% of incorporated nitrogen. Control of the antiphase disorder allows to tune mean film polarity and second order nonlinear optical response of III-phosphide heterostructures.

The heterostructure of light-emitting diode on a silicon substrate with an active region based on A3B5N was synthesized and investigated. Light-emitting diode demonstrates effective electroluminescence at 645 nm up to the 360 K. This indicates the high crystalline and optical quality of the light-emitting structure, as well as the prospects of this approach for the development of silicon integrated photonics.

The transformation of the properties of the bases by the method of deep soil mixing allows the construction of buildings and structures on sites with soft soils. As a rule, adverse geological conditions are accompanied by the presence of dynamic effects on the designed buildings. The objective of this research is to forecast changes in the mechanical properties of the base under dynamic loads. The object of study is the propagation velocity of elastic shear waves, since these parameters significantly affect the calculations of deformations and stability of earthquake-resistant industrial and civil buildings and structures, as well as objects of energy and transport construction. The paper contains a review of similar studies, on the basis of which the conclusions obtained during the experiments are further generalized. Based on the analysis of the results of laboratory tests performed by the authors of this work, by the method of low-amplitude torsion vibrations in a resonant column in the anisotropic triaxial compression mode, the influence of the density of soil cement samples, humidity, and additional load on the propagation velocity of elastic transverse waves is estimated. The paper provides a description of the essence of the research method, a review of the equipment on which special laboratory tests were performed. The tests were carried out on samples of unbroken soil cement taken from the base of a nuclear power plant (NPP) under construction. Dried samples of soil cement were investigated, and tests were carried out at full water saturation and at a given humidity. The anisotropic stress state of soil cement samples during triaxial tests in a resonance column was due to the features of the base of the designed NPP. Studies have shown that the most significant factor affecting the shear wave velocity is the additional vertical load. It is noted that with increasing density, the velocity of the shear waves decreases. Humidity is directly related to the density of soil cement and the amount of water in the pores, so the assessment of its effect on the dynamic properties of soil cement is similar to the effect of changes in density.

The growth of monolith GaAsP/Si dual-junction solar cells on Si substrates by molecular-beam epitaxy is demonstrated. The technological method for the formation of a highly doped tunnel p+/n+ junction was developed. An obvious increase in the value of the open-circuit voltage indicating the contribution of the top-junction in the total open-circuit voltage monolithic dual-junction solar cells was found.

The article presents a set of calibration techniques for thermal imaging systems calibration. The proposed algorithms allow high-precision calibration of the IR photodetector with finding and subsequent correction of the entire spectrum of defective pixels: by noise, amplitude and sensitivity. Part of the work is devoted to the development of methods for correcting the influence of ambient temperature on the optical system of a thermal imaging channel, which helps to prevent the effect of super saturation of the IR image pixels.

In this report we present design and first experimental results for development of the submm superconducting integrated receiver spectrometer for Terahertz Limb Sounder (TELIS). TELIS is a collaborative European project to build up a three-channel heterodyne balloon-based spectrometer for measuring a variety of atmospheric constituents of the stratosphere. The 550 - 650 GHz channel of TELIS is based on a phase-locked Superconducting Integrated Receiver (SIR). SIR is an on-chip combination of a low-noise Superconductor-Insulator-Superconductor (SIS) mixer with quasioptical antenna, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO), and SIS harmonic mixer (HM) for FFO phase locking. A number of new solutions were implemented in the new generation of SIR chips. To achieve the wide-band performance of the spectrometer, a side-feed twin-SIS mixer and balanced SIS mixer with 0.8 µm2 junctions integrated with a double-dipole (or double-slot) antenna is used. An improved design of the FFO for TELIS has been developed and optimized providing a free-running linewidth between 10 and 2 MHz in the frequency range 500 - 700 GHz. It is important to ensure that tuning of a phase-locked (PL) SIR can be performed remotely by telecommand. For this purpose a number of approaches for the PL SIR automatic computer control have been developed. All receiver components (including input optical elements and Martin-Puplett polarization rotating interferometer for single side band operation) will be mounted on a single 4.2 K plate inside a 40 × 180 × 80 mm3 box. First measurements give an uncorrected double side band (DSB) noise temperature below 250 K measured with the phase-locked FFO; more detailed results are presented at the conference.

The FFO is a long Josephson junction in which the flow of magnetic flux quanta, and thus the oscillator frequency is controlled by the DC bias current IB, and the DC current ICL producing the magnetic field at the junction ends. We have experimentally studied the properties of the Nb/AlOx/Nb and Nb/AlN/Nb trilayer FFOs when IB also contributes to the magnetic field. A number of samples were fabricated, each containing an FFO integrated with a bias current loop designed so that the bias current can generate approximately the same positive or negative contribution to the magnetic fields at both ends of the FFO. The magnetic field is proportional to ICL + Lp*IB, where Lp is given by the loop design. We have made a study of both the DC parameters and the radiation linewidth for FFOs with different integrated loops and compared our results to that for the FFO without any loop. It was found that loops with positive contribution (Lp > 0) make the FFO linewidth smaller (although the differential resistance of the FFO on the bias current becomes larger), while loops with negative contribution (Lp < 0) result in broadening of the FFO radiation linewidth. The magnitude of this effect strongly depends on the critical current density JC ~ (Rn*S)−1. The Rn*S product was varied in our experiments from 13 to 35 Ohm*µm2. We propose a possible explanation of this effect.

The structural properties of GaP(As)N dilute nitrides alloys grown on GaP substrates by molecular-beam epitaxy are investigated. The samples were studied by Raman scattering and high-resolution X-ray diffraction. In this work the impact of lattice mismatch of GaP(As)N layer and GaP substrate on the form of the spectrum of Raman scattering of samples was detected. It was shown that the addition of arsenic in solid solution GaPAsN can compensate the elastic stresses in the crystal lattice, and we can estimate the lattice mismatch between epitaxial layer GaP(As)N and GaP substrate by the intensity ratio of LOX/TOr phonon peaks.

A Flux-flow oscillator based on a long Josephson junction is a local oscillator in fully superconducting integrated receivers (SIRs). The low frequency voltage fluctuations define the free-running FFO radiation linewidth, an important parameter for employing the SIR as a submm spectrometer. The DC voltage of the oscillator is independently controlled by both the dissipative DC bias current IB and the loss-free external magnetic field at the two FFO ends. It is mainly the natural wideband current noise of the Josephson barrier, which is converted into the fluctuations of voltage by the differential resistance Rd on the current IB. We have developed and experimentally demonstrated the method for suppression of the voltage fluctuations by convey of the bias current noise into the anticorrelated noise of the magnetic field. The experiments were made with Nb/AlN/Nb FFOs, having a specially designed shunting structure at the end, where flux quanta enter the junction.

We have numerically investigated the dynamics of a long linear Josephson tunnel junction with overlap geometry (Flux-Flow Oscillator, FFO). The study is performed in the frame of a modified sine-Gordon model, which includes surface losses, self-pumping effect, and in an empirical way the superconducting gap. The electromagnetic coupling to the environment is modeled by a simple resistor-capacitor load (RC-load) placed at both ends of the FFO. In our model the damping parameter depends both on the spatial coordinate and on the amplitude of the AC voltage. In order to find the DC current-voltage curves the damping parameter has to be calculated self-consistently by successive approximations and time integration of the perturbed sine-Gordon equation. The modified model gives better qualitative agreement with experimental results than the conventional perturbed sine-Gordon model.

A Flux-Flow Oscillator (FFO) is a long Josephson junction in which a unidirectional flow of magnetic flux quanta is maintained by an applied DC magnetic field and a bias current. In the overlap geometry the FFO voltage and thus its oscillation frequency is controlled independently by the (overlap) bias current and the so-called "control line" (inline) current, which creates the magnetic field at the ends of the FFO. We have studied both DC properties and the linewidth of the emitted radiation for an FFO, which can be biased in different ways; as a four current terminal object. The bias current of the mixed inline-overlap type is applied through the terminals commonly used for the "control line" current. In this configuration the bias current also contributes to the magnetic field at one of the two FFO ends. This changes the steepness of the junction's I-V characteristics and therefore the bias current dynamic resistance. The experimental FFO linewidth was found to be independent of the bias configuration and determined by the dynamic resistance of the junction with pure overlap bias current. A new method has been developed to evaluate the difference in the DC magnetic field at the ends of the junction. It may be attributed to control line redistribution caused by the impedance matching RF circuit connected to the FFO at the end where the fluxon chain annihilates and radiation is emitted. We found that the opposite end, where the fluxons enter the junction, appears to be about three times more sensitive to variations of the magnetic field than the radiating end.