A room-temperature terahertz (THz) detector based on a thermoelectric frequency selective surface (FSS) has been numerically simulated, designed, fabricated, and tested. The FSS has been fabricated from a 150 nm thin Bi₈₈Sb₁₂ thermoelectric film with the engraved periodic Greek crosses. The detector prototype has been tested under the 0.14 THz radiation exposure and showed a voltage response due to the photo-thermoelectric effect up to 0.13–0.18 mV, and voltage responsivity equal to 14–20 mV/W. The detector based on the FSS has shown voltage responsivity up to three times higher in comparison with the detector based on the continuous film. Thermal imaging has shown a temperature increase in the FSS up to 1.5 K under the THz exposure. The obtained results demonstrate prospects for utilization of the Bi₈₈Sb₁₂ FSS detector as a low cost, compact, high-speed, highly sensitive room-temperature THz detector.

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.

We report a numerical study of the field assisted sintering of silicon germanium alloys by a finite element method, which takes into account contact resistances, thermal expansion and the thermoelectric effect. The distribution of electrical and thermal fields was analyzed numerically, based on the experimental data collected from spark plasma sintering (SPS) apparatus. The thermoelectric properties of Si-Ge used within the simulation were considered as the function of density and the sintering temperature. Quantitative estimation of the temperature distribution during the sintering pointed to a significant, up to 60 °C, temperature difference within the specimen volume for the case of the sintering temperature at 1150 °C.

A process of fabrication of thermoelectrics by the spark plasma sintering (SPS) method to obtain materials with advanced properties is simulated. The effect of the die dimensions and geometry on the temperature field distribution inside the sintered sample is analyzed. The feasibility of fabrication of functionally graded materials by the SPS process using dies of special configuration is demonstrated.