Bulk crystals of β-Ga2O3 were successfully grown by the edge-defined film-fed growth method. The crystalline quality of the obtained crystals was analyzed by the method of x-ray diffractometry. The full width at half maximum of the rocking curve was about 72 arcsec. The optical bandgap was determined by analyzing the optical transmission spectra and amounted to 4.7 eV. The hot disk method was used to obtain the thermal conductivity of the sample along the [001] direction in the temperature range from 30 to 120 °C. The maximum value of thermal conductivity obtained at 30 °C was 9.25 W/(m K).

We report results of galvanomagnetic and terahertz time-domain spectroscopy measurements on thin films of Bi ${}_{1-x}$ Sb ${}_x$ on polyimide and mica substrates with various antimony concentrations (x from 0 to 15 %) and film thickness (70, 150 nm). The resistivity, Hall coefficient and magnetoresistivity of the films were measured experimentally in the magnetic field of 0.65 T at room temperature. Mobility and concentration of electrons and holes in the film plane were calculated using the transport coefficients. The terahertz time-domain spectroscopy is used to measure the complex conductivity and permittivity of Bi ${}_{1-x}$ Sb ${}_x$ thin films on the dielectric substrates in the frequency range from 0.2 to 1 THz. The plasma frequency, relaxation time, DC conductivity and effective carrier mass were extracted from these data and evaluated as functions of the Sb concentration for different film thickness and substrate. We observed that the film magnetoresistivity decreases with increasing the Sb concentration and for most of the films the Hall coefficient is negative and depends on the external factors insignificantly. We show that the mobility of charge carriers weakly depends on Sb concentration, which confirms the assertion about the scattering of carriers on themselves and not on defects in the structure. It was revealed that film static and dynamic resistivity (conductivity) as well as dielectric permittivity depend on Sb content and the film thickness. The results may be used for development of various thermoelectric, electronic and optical devices, such as THz detectors or components which can control the properties of THz radiation.

A terahertz (THz) detector based on thermoelectric thin films was simulated using the finite elements method. The thermoelectric circuit consisted of $Sb$ and $B{i}_{88}S{b}_{12}$ 150-nm films on the mica substrate. $Sb$ , $B{i}_{88}S{b}_{12}$ , and mica-substrate properties have been measured experimentally in the THz frequency range. The model of electromagnetic heating was used in order to estimate possible heating of $Sb$ - $B{i}_{88}S{b}_{12}$ contact. THz radiation power varied from 1 $\mathsf{\mu }$ W to 50 mW, and frequency varied in the range from 0.3 to 0.5 THz. The calculations showed a temperature difference of up to 1 K, voltage up to 0.1 mV, and responsivity of several mVW ${}^{-1}$ . The results show that thin $Sb$ and $Bi-Sb$ thermoelectric films can be used for THz radiation detection at room temperatures.

Whole body cryotherapy is a state-of-the-art method that uses cold for treatment and prevention of diseases. The process implies the impact of cryogenic gas on a human body that implements in a special cryochamber. The temperature field in the chamber is of great importance since local integument over-cooling may occur. Numerical simulation of WBC has been carried out. Chamber design modification has been proposed in order to increase the uniformity of the internal temperature field. The results have been compared with the ones obtained for a standard chamber design. The value of temperature gradient formed in the chamber containing curved wall with certain height has been decreased almost twice in comparison with the results obtained for the standard design. The modification proposed may increase both safety and comfort of cryotherapy.

The terahertz frequency range is promising for solving various practically important problems. However, for the terahertz technology development, there is still a problem with the lack of affordable and effective terahertz devices. One of the main tasks is to search for new materials with high sensitivity to terahertz radiation at room temperature. Bi_1−xSb_x thin films with various Sb concentrations seem to be suitable for such conditions. In this paper, the terahertz radiation influence onto the properties of thermoelectric Bi_1−xSb_x 200 nm films was investigated for the first time. The films were obtained by means of thermal evaporation in vacuum. They were affected by terahertz radiation at the frequency of 0.14 terahertz (THz) in the presence of thermal gradient, electric field or without these influences. The temporal dependencies of photoconductivity, temperature difference and voltage drop were measured. The obtained data demonstrate the possibility for practical use of Bi_1−xSb_x thin films for THz radiation detection. The results of our work promote the usage of these thermoelectric materials, as well as THz radiation detectors based on them, in various areas of modern THz photonics.