The study of the origin and transport of water in the universe is an important part of the scientific program of the Millimetron space observatory. This will be made possible by observations conducted in single-dish mode using an onboard instrument-the high-resolution spectrometer (HRS). This instrument incorporates heterodyne array receivers operating within the range 0.5 -2.7 THz, comprising 3-pixel arrays of superconductor-insulator-superconductor mixers operating at frequencies below 1.3 THz and 7-pixel matrix receivers based on NbN HEB mixers observing above 1.3 THz. This article presents the current status of development for a mixers planned for use in the HRS instrument of the Millimetron space observatory.

In this paper, model of a surface ion trap for a scalable quantum computer with an RF electrode and a superconducting single-photon detector was studied with an operating temperature of 4 K. The amplitude range of the radio frequency signal varied from 10 to 800 mV at frequencies from 5 to 20 MHz. The effect of the induced external RF field of the trap on the dark and bright count rate of a single-photon detector is studied. The results of this work are important in the design of surface ion traps with planar single-photon detectors.

In this paper, model of a surface ion trap for a scalable quantum computer with an RF electrode and a superconducting single-photon detector was studied with an operating temperature of 4K. The amplitude range of the radio frequency signal varied from 10 to 800 mV at frequencies from 5 to 20 MHz. The effect of the induced external RF field of the trap on the dark and bright count rate of a single-photon detector is studied. The results of this work are important in the design of surface ion traps with planar single-photon detectors.

Here, we report on our recent efforts to develop of a photodetector based on single-layer graphene two-terminal device on the sapphire substrate. Our detector operates at $1.55 \mu \mathrm{m}$, which corresponds to the telecom window. We have demonstrated that our detector operates under zero bias conditions at room temperature, and the signal-to-noise ratio reaches 45dB. The measured frequency bandwidth reaches 20GHz and is limited by the available experimental equipment.

ilia1999ven@gmail.com Abstract. In this work we describe fabrication of diffraction gratings for generation of light with orbital angular momentum (OAM). OAM light characterized by topological charge l and modes with different l are orthogonal, which makes OAM light useful in quantum communication and tomography. We demonstrate fabrication route of diffraction gratings with computer generated hologram pattern on sapphire substrate and niobium reflective coat for generation of OAM light of visible spectrum.

In this paper, we report on the method of nondestructive quality control that can be used in fabrication of GaAs high-speed electronics. The method relies on the surface potential mapping and enables rigid in vivo analysis of transport properties of an active electronic device incorporated into a complex integrated circuit. The study is inspired by our ongoing development of a millimeter wave intelligent reflective surface for 6G communications. To provide desired beamforming capabilities, such a surface should utilize hundreds of identical microscale GaAs diode switches with series resistance of a few ohms. Thus, we develop a ladder-like layered ohmic contact to heavily Si-doped GaAs and cross-study it via transmission line method and Kelvin probe force microscopy. The contact resistivity as low as 0.15 μΩcm^2 is measured resulting in only a 0.6 Ω of resistance for the contact area of 3×3 μm^2. Moreover, the tendencies observed suggest that one can rigidly analyze the evolution of contact resistance and the profile of resistivity under contact in response to rapid thermal annealing, once the surface potential map across the “ladder” is known.

In the 20th 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.

We report on the inelastic-scattering rate of electrons on phonons and relaxation of electron energy studied by means of magnetoconductance, and photoresponse, respectively, in a series of strongly disordered superconducting NbN films. The studied films with thicknesses in the range from 3 to 33 nm are characterized by different Ioffe-Regel parameters but an almost constant product ${q}_{T}l$ (${q}_{T}$ is the wave vector of thermal phonons and $l$ is the elastic mean free path of electrons). In the temperature range 14--30 K, the electron-phonon scattering rates obey temperature dependencies close to the power law $1/{\ensuremath{\tau}}_{\mathrm{e}\text{\ensuremath{-}}\mathrm{ph}}\ensuremath{\sim}{T}^{\mathrm{n}}$ with the exponents $n\ensuremath{\approx}3.2--3.8$. We found that in this temperature range ${\ensuremath{\tau}}_{\mathrm{e}\text{\ensuremath{-}}\mathrm{ph}}$ and $n$ of studied films vary weakly with the thickness and square resistance. At 10 K electron-phonon scattering times are in the range 11.9--17.5 ps. The data extracted from magnetoconductance measurements were used to describe the experimental photoresponse with the two-temperature model. For thick films, the photoresponse is reasonably well described without fitting parameters, however, for thinner films, the fit requires a smaller heat capacity of phonons. We attribute this finding to the reduced density of phonon states in thin films at low temperatures. We also show that the estimated Debye temperature in the studied NbN films is noticeably smaller than in bulk material.

In the 20th 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.

Plasmonic interferometry is a rapidly growing area of research with a huge potential for applications in terahertz frequency range. In this Letter, we explore a plasmonic interferometer based on graphene Field Effect Transistor connected to specially designed antennas. As a key result, we observe helicity- and phase-sensitive conversion of circularly-polarized radiation into dc photovoltage caused by the plasmon-interference mechanism: two plasma waves, excited at the source and drain part of the transistor interfere inside the channel. The helicity sensitive phase shift between these waves is achieved by using an asymmetric antenna configuration. The dc signal changes sign with inversion of the helicity. Suggested plasmonic interferometer is capable for measuring of phase difference between two arbitrary phase-shifted optical signals. The observed effect opens a wide avenue for phase-sensisitve probing of plasma wave excitations in two-dimensional materials.

In this paper we report on the fabrication of a planar Schottky diode utilizing a Г-shaped anode suspended bridge. The bridge maintains transition between the top and bottom level planes of a 1.4 µm thick GaAs mesa. To implement the profile of a suspended bridge and inward tilt of a mesa wall adjacent to it, we make use of an anisotropic etching of gallium arsenide. The geometry proposed enables the fabrication of a diode with mesa of an arbitrary thickness to mitigate AC losses in the diode layered structure at terahertz frequencies of interest. For frequencies beyond 1 THz, it is also beneficial to use the geometry for the implementation of n-GaAs/n-InGaAs heterojunction Schottky diodes grown on InP substrate.

We report an experimental study of the band structure of individual carbon nanotubes (SCNTs) based on investigation of the tunneling density of states, i.e. tunneling spectroscopy. A common approach to this task is to use a scanning tunneling microscope (STM). However, this approach has a number of drawbacks, to overcome which, we propose another method ? tunneling spectroscopy of SCNTs on a chip using a tunneling contact. This method is simpler, cheaper and technologically advanced than the STM. Fabrication of a tunnel contact can be easily integrated into any technological route, therefore, a tunnel contact can be used, for example, as an additional tool in characterizing any devices based on individual CNTs. In this paper we demonstrate a simple technological procedure that results in fabrication of good-quality tunneling contacts to carbon nanotubes.

In this paper we report on the results of investigation of efficiency of a microwave reflectometry for readout of a terahertz multipixel Schottky diode direct detector. Decent capabilities of the microwave reflectometry readout were earlier justified by us for a hot electron bolometric direct detector. In case of a planar Schottky diode, we observed increase of an optical noise equivalent power by a factor of 2 compared to that measured within a conventional readout scheme. For implementation of a multipixel camera, a microwave reflectometer is to be used to readout each row of the camera, and the row switching is to be maintained by a CMOS analog multiplexer. The diodes within a row have to be equipped with filters to distribute the probing microwave signal properly. The simultaneous use of analog multiplexing and microwave reflectometry enables to reduce the camera response time by a factor of its number of columns.

We present an elegant and effective technology of extending the photoresponse of Si towards the IR range. Our approach is based on the use of Ag2S quantum dots planted on the surface of Si to create impurity states in Si band gap. Given the variety of available QDs and the ease of extending the photoresponse of Si towards the IR range, our findings open a path towards the future study and development of Si detectors for technological applications. The current research at the interface of physics and chemistry is also of fundamental importance to the development of Si optoelectronics of the IR range.

We report on the signal-to-noise and gain bandwidth of a niobium nitride (NbN) hot-electron bolometer (HEB) mixer at 2 THz fabricated on a sapphire substrate with a GaN buffer layer. Two mixers with different DC properties and geometrical dimensions were studied and they demonstrated very close bandwidth performance. The signal-to-noise bandwidth is increased to 8 GHz in comparison to the previous results, obtained without a buffer-layer. The data were taken in a quasi-optical system with the use of the signal-to-noise method, which is close to the signal levels used in actual astrophysical observations. We find an increase of the gain bandwidth to 5 GHz. The results indicate that prior results obtained on a substrate of crystalline GaN can also be obtained on a conventional sapphire substrate with a few micron MOCVD-deposited GaN buffer-layer.

We report on the bandwidth performance of the normal metal TiN bolometer-mixer on top of an Al2O3 substrate, which is capable to operate in a wide range of bath temperatures from 77 K – 300 K. The choice of the combination TiN / Al2O3 is related to an advanced heat transport between the film and the substrate in this pair and the sufficient temperature coefficient of resistance. The data were taken at 132.5 – 145.5 GHz with two BWOs as a signal and an LO source. Measurements were taken on TiN films of different thickness starting from 20 nm down to 5 nm coupled into a spiral Au antenna, which improves matching of incoming radiation with the thin TiN fim. Our experiments demonstrate effective heat coupling from a TiN thin film to an Al2O3 substrate (111) boosting gain bandwidth (GB) of TiN bolometer up to 6 GHz for 5 nm thin film. Current results indicate weak temperature dependence of GB on the bath temperature of the TiN bolometer. Theoretical estimations of GB performance meet with experimental data for 5 nm thin TiN films.

In the work the thicknesses of the e-beam resists ZEP 520A and ma-N 2400 by using non-destructive method were measured, as well as recipe for the high ratio between the Si3N4 and the resists etching rate was determined. The work has a practical application for e-beam lithography of photonic-integrated circuits and nanophotonics devices based on silicon nitride platform.

We present the results of characterization of fast and sensitive superconducting antenna-coupled THz direct detector based on NbN hot-electron bolometer (HEB) with AC-bias. We discuss the possibility of implementation of the AC-bias for design the readout system from the multi-element arrays of HEBs using standard technique of frequency-domain multiplexing. We demonstrate experimentally that this approach does not lead to significant deterioration of the HEB sensitivity compared with the value obtained for the same detector with DCbias. Results of a numerical calculations of the HEB responsivity at AC-bias are in a good agreement with the experiment.

—The influence of homogeneity disorder degree of the thin superconducting NbN film across of Si wafer on characteristics of the Hot Electron Bolometers (HEB) has been investigated. Our experiments have been carried out near the superconducting transition and far below it. The high homogeneity disorder degree of the NbN film has been achieved by preparing the Si substrate surface. The fabricated HEBs all have almost identical R (T) characteristics with a dispersion of Tc and the normal resistance R300 of not more than 0.15K and 2 Ω, respectively. The quality of the devises allows us to demonstrate clearly the influence of non-equilibrium processes in the S’SS’ system on the device performance. Our fabrication technology also allows creating multiplex heterodyne and direct detector matrices based the HEB devices.

In this paper, we report on the results of the study of the Ti/Au/n-GaAs planar Schottky diodes (PSD) intended for the wideband detection of terahertz radiation. The two types of the PSD devices were compared having either the dual n/n(+) silicon dopant profile or the triple one with a moderately doped matching sublayer inserted. All the diodes demonstrated no noticeable temperature dependence of ideality factors and barrier heights, whose values covered the ranges of 1.15-1.50 and 0.75-0.85 eV, respectively. We observed the lowering of the flat band barrier height of similar to 80 meV after introducing the matching sublayer into the GaAs sandwich. For both the devices types, the series resistance value as low as 20 Omega was obtained. To extract the total parasitic capacitance, we performed the Y-parameters analysis within the electromagnetic modeling of the PSD's behavior via the finite-element method. The capacitance values of 12-12.2 fF were obtained and further verified by measuring the diodes' response voltages in the frequency range of 400-480 GHz. We also calculated the AC current density distribution within the layered structures similar to those being experimentally studied. It was demonstrated that insertion of the moderately Si-doped matching sublayer might be beneficial for implementation of a PSD intended for the operation within the 'super-THz' frequency range.