In the 20^th century, microelectronics was revolutionized by silicon—its semiconducting properties finally made it possible to reduce the size of electronic components to a few nanometers. The ability to control the semiconducting properties of Si on the nanometer scale promises a breakthrough in the development of Si-based technologies. In this paper, we present the results of our experimental studies of the photovoltaic effect in Ag₂S QD/Si heterostructures in the short-wave infrared range. At room temperature, the Ag₂S/Si heterostructures offer a noise-equivalent power of 1.1 × 10⁻¹⁰ W/√Hz. The spectral analysis of the photoresponse of the Ag₂S/Si heterostructures has made it possible to identify two main mechanisms behind it: the absorption of IR radiation by defects in the crystalline structure of the Ag₂S QDs or by quantum QD-induced surface states in Si. This study has demonstrated an effective and low-cost way to create a sensitive room temperature SWIR photodetector which would be compatible with the Si complementary metal oxide semiconductor technology.

The sixth-generation cellular systems are expected to utilize the sub-terahertz frequency band covering 100-300 GHz. Due to high path losses, the coverage of such systems will be limited to a few tens of meters making them suitable for indoor environments. As compared to outdoor deployments, indoor usage of sub-terahertz systems is characterized by the need to operate over shorter distances using both line-of-sight (LoS) and in-reflection propagation paths. This potentially results not only in the attenuation of radio signal, but in the appearance of diffraction signatures in its time-related metrics too. We conduct a detailed measurement campaign at the carrier frequency of 156 GHz and report on the dynamics of the reflection and blockage losses as well as signal fall, blockage, and recovery times over various in-reflection paths. We also develop reflection model and use it to extract the complex permittivities of glass, drywall and aerated concrete from their measured reflection spectra. The extracted permittivities of 7.23+0.22 i , 2.63+0.026 i , 1.9+0.017 i are consistent with the material-dependent reflection losses, which are as high as 16 dB for transverse electric (TE)-polarized and 39 dB for transverse magnetic (TM)-polarized signals. Moreover, the asymmetry in the side lobe levels of the transmitting and receiving antenna beams results in the additional losses ranging from 16 to 49 dB as measured for 3.55-4.3 m long non-specular paths with the angles of departure and reception within 30-70°. The blockage losses, in turn, are in the range of 6-17 dB. We observe that the presence of a re-directing material does not affect their mean value. However, the acquired blockage duration, signal fall and recovery times are noticeably smaller than in the LoS channels with the same directivity. This implies that the time-budget for blockage detection is much smaller: it reduces to just 20-40 ms as compared to 80-100 ms intrinsic to the LoS propagation paths.

The quality of wireless connections in the sixth generation (6G) communication networks is tightly linked to the capabilities of smart antenna environments. They should enable effective routing of ultra-narrow radio beams, intrinsic to D-band channels, and make use of so-called reconfigurable intelligent surfaces (RISs). Practical RISs are seriously judged by their cost and operation efficiencies. In this paper, we report on the development of a robust single-port antenna that can be used as part of a D-band RIS panel. The antenna is presented by a grounded log-periodic spiral on thin quartz substrate. Two types of spirals are developed for either a static beamforming or dynamic beam steering in reflected light. The geometry- and load-controlled phase shifts consistently cover a 0–350 $^\circ$ range upon reflection of 140 GHz waves with the angles of incidence within $\pm 75^\circ$ . This is achieved by changing either i) the spiral scaling factor between 0.658 and 1 in half-wave cells or ii) the spiral load capacitance between 0 fF and 20 fF in quarter-wave cells. These values are feasible for GaAs-on-quartz planar Schottky diodes. The simulation results are justified by prototyping. For a 1.3k pixel proof-of-concept reflectarray with geometrically phase-configured cells, we measure the beamwidth, side lobe and cross-polarization levels of 4 $^\circ$ , $-$ 13 dB and $-$ 26 dB, respectively. All together suggests great potential of the developed antennas as basic elements for the physical layer devices of reflection-aided 6G wireless communications.