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.

Terahertz (THz) filters and detectors can find a wide application in such fields as: sensing, imaging, security systems, medicine, wireless connection, and detection of substances. Thermoelectric materials are promising basis for THz detectors’ development due to their sensitivity to the THz radiation, possibility to be heated under the THz radiation and produce voltage due to Seebeck effect. Thermoelectric thin films of Bi-Sb solid solutions are semimetals/semiconductors with the band gap comparable with THz energy and with high thermoelectric conversion efficiency at room temperature. Detecting film surface can be transformed into a periodic frequency selective surface (FSS) that can operate as a frequency filter and increases the absorption of THz radiation. We report for the first time about the simulation of THz detector based on thermoelectric Bi-Sb thin-filmed frequency-selective surface. We show that such structure can be both detector and frequency filter. Moreover, it was shown that FSS design increases not only a heating due to absorption but a temperature gradient in Bi-Sb film by two orders of magnitude in comparison with continuous films. Local temperature gradients can reach the values of the order of 100 K· mm−1. That opens new perspectives for thin-filmed thermoelectric detectors’ efficiency increase. Temperature difference formed due to THz radiation absorption can reach values on the order of 1 degree. Frequency-transient calculations show the power dependence of film temperature on time with characteristic saturation at times around several ms. That points to the perspective of reaching fast response times on such structures.

Terahertz radiation is very promising for visualization, detection and data transfer. Searching for sensitive, fast and compact THz detector that operates at room temperature is a common subject for these applications. Hence, there is still an issue of searching for new materials for THz radiation detection. Solid solutions based on thermoelectric bismuth and antimony appear to have significant potential for these applications. In this paper photoresponse of thermoelectric material Bi88Sb12 has been studied for the first time. Films with thicknesses of 70 and 150 nm were studied under influence of radiation at frequency of 0.14 THz. Keywords: terahertz radiation, photoresponse, bismuth, antimony, thermoelectric materials, thin films.