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A miniature planar meander-type slow-wave structure (SWS) for a W-band traveling-wave tube is studied. Computer simulation of the SWS electrodynamic parameters is performed. A new technology for fabrication of planar microstrip SWSs with the aid of laser ablation is proposed. The S-parameters of the SWS are experimentally studied. The experimental data are in good agreement with the results of the 3D computer simulation. Output characteristics of the traveling-wave tube with a sheet electron beam and planar SWS are calculated.

—The effect of low-dose γ radiation on the mechanisms of low-frequency conductivity of mesoporous silicon has been studied. It has been shown that γ irradiation preserves the hopping character of conductivity at a change of the frequency of phonon lattice vibrations, a decrease in the size of the hop, and a shift of the level of the capture of traps to the Fermi level in the band gap, which makes the structure with mesoporous silicon irradiated by γ radiation promising for the creation of multifunctional resistive and capacitive devices.

Application of higher harmonics generation mode in a compact low-voltage vircator-type vacuum electronic device utilizing nonlaminar electron beams operating in millimeter band is considered and preliminary experimental results are reported. Higher harmonics generation was achieved by formation of translaminar electron layer through the choice of the optimal voltages for the control electrode and electron beam inhibition by the electrostatic field of the collector. This approach allowed for dense electron grouping in nonlaminar electron beams that provided the growth of the amplitude of the higher harmonics in the output power spectrum. In this system, the increase of the fundamental operating frequency by application of external magnetic field was experimentally demonstrated. If combined with higher harmonics generation mode, this can lead to significant increase of resulting operating frequency of the compact low-voltage system to millimeter wavelength band.

Results of experimental study of the reflection and transmission losses in the V-band of µm-thick Si-Al films on the dielectric substrates are considered. Two sources magnetron co-sputtering deposition of Si-Al alloys was utilized to prepare a series of coatings of varied chemical composition and thus different properties. Control over films composition was provided by variation of Al magnetron power source with constant Si magnetron power source. Segregation of Si and Al atoms in Al-Si films was observed at a specific power of Al magnetron source during the deposition: Si atoms were mainly concentrated at the lower levels of the film adjacent to the substrate, while Al atoms tended to concentrate near the upper surface of the coating. Distinct electromagnetic properties of Al-Si films fabricated at the transient phase of segregation mode were observed: one side of the film demonstrated low reflection in the millimeter-band while almost full reflection was observed from the other side. Such properties of µm-thick Si-Al films upon dielectric substrates can be useful for development of millimeter-wave antenna modules technology.

The goal of this work is an investigation of peculiarities of the molybdenum-copper alloys formation by magnetron sputtering to meet the requirements of low thermal expansion coefficient together with high electrical/thermal conductivity of the material for potential use in microfabrication of slow-wave structures for miniaturized millimeter-band vacuum electron devices. The study is focused on controlling the roughness and adhesion of the fabricated thin Cu-Mo alloy films. The roughness mainly determines the transmission losses at millimeter and THz frequencies, whereas the adhesion of the film is quite important for further processing, such as laser ablation.

Travelling-wave-tube (TWT) power amplifiers with planar microstrip slow wave structures (SWS) on dielectric substrates are very promising for operation at high frequencies due to their low-voltage operation, small size and relatively high output power. Recently, the interest to the planar SWSs has increased since their using can significantly decrease the complexity of microfabrication process. In our previous work, we reported successful fabrication of millimeter-band microstrip planar SWSs using the scalable and cost-effective laser ablation process with nanosecond pulse duration. However, the SWS samples fabricated by nanosecond laser ablation suffer from surface distortions and debris on the borders of the ablated zone. In order to improve the quality of resulting structures, here we propose deposition of a supplementary metallic (Al or Ti) layer on top of copper film prior to laser treatment. Such coating is aimed to prevent defects formation in the course of laser irradiation. In the proposed system, debris and distortions from Cu layer irradiation, naturally sediment on the sacrificial layer instead of sticking to the copper layer itself. Sacrificial aluminium coating can later be easily chemically removed together with sedimented debris leaving a clean underlying patterned Cu surface. In contrast, titanium layer prevents sticking of copper debris due to the higher melting temperature of Ti, thus preventing attachment of those to the surface in the first place.

We have designed D-bandplanar meander-line slow wave structure for low voltage compact traveling-wave tubes (TWTs) with sheet electron beam. The designed D-band slow wave structure was microfabricated by magnetron sputtering and picoseconds laser ablation. We further develop our approach for planar slow wave structure microfabrication based on magnetron sputtering and laser ablation processes. Transmission and reflection losses of proposed SWS were measured experimentally and evaluated numerically. The experimental results are in good agreement with the numerical ones.

Sources of millimeter and submillimeter (terahertz) band radiation are very important in modern society due to their broad application from telecommunication to non-destructive evaluation and chemical analysis. In this work, we present a review of technological approaches for fabrication of RF structures of µVEDs. Technological approaches to the microfabrication of planar slow-wave structures (SWS) on dielectric substrates operating with a sheet electron beam are considered. Such SWSs are attractive due to the simplicity of the structure, compact dimensions, low voltage operating, and wide bandwidth. We consider lithography-based technology, deep reactive ion etching, computer-numerical-control (CNC) micro- and nano-milling, electrical discharge micromachining, and technologies based on the additive manufacturing such as three-dimensional (3-D) printing, selective laser sintering, and selective laser melting. We also describe an original approach to microfabrication of planar structures based on magnetron sputtering and CNC laser ablation. Fabrication tolerance and surface roughness provided by the considered technologies are compared.

Nowadays vacuum electron devices still remain the main sources of high power coherent and broadband millimeterwave radiation. Among electron beam sources the pseudospark discharge can be distinguished as a promising pulsed plasma electron beam source. The reason is that the pseudospark discharge sourced electron beam has the ability to self-focus due to the unique discharge structure and the formation of the ion channel generated by the beam front. The ion channel enables the electron beam to propagate and eliminates the need for a guiding magnetic field. Therefore the development of compact and high-power vacuum electron devices utilizing a pseudospark discharge based hollow cathode electron gun is one of the promising trends. Here the results of the design, optimization and development of a pseudospark-based high-current-density sheet electron beam source are presented. A slow-wave structure for the backward-wave oscillator driven by a pseudospark-sourced sheet electron beam was also designed and numerically studied. Preliminary results of numerical simulations of electrodynamic characteristics of the suggested slow-wave structure are shown. We are going to use a CNC-micro milling based technological approach to microfabricate the designed slow-wave structure. The first steps of microfabrication results are also presented.

Development of millimeter and submillimeter-band (THz-band) vacuum electronic devices put forward special requirements to the properties of structural materials for microfabrication of such basic electronic components as slow-wave structures. One of the promising composite materials for vacuum microelectronic devices is molybdenum-copper alloys. This composite combines high thermal and electrical conductivity of copper and low thermal expansion of molybdenum. The influence of the composition of molybdenum-copper alloy on the electrodynamics parameters (S-parameters) of the slow-wave structure was revealed with the help of numerical simulation. Two sources magnetron co-sputtering can be utilized for Mo-Cu alloys deposition with the resulting composition of the alloy controlled by varying the power of the magnetron sources, working gas pressure and the substrate temperature.

Metamaterials recently attracted a wide interest in many areas of scientific research. Particularly, application of metamaterials is very promising in vacuum electronics devices of mm and sub-THz range. Dielectric substrate with metamaterials coating was used in several devices such as travelling wave tubes and backward wave oscillators. Use of metamaterials can be quite attractive if electrical properties of those can be controlled, for example, through the variation of basic materials properties. Here Si-A1 alloy is suggested as the base material for metamaterial formation. Two source magnetron co-sputtering deposition of Si-A1 alloys was utilized to obtain series of coatings with different chemical composition and thus different resistivity. Control of composition was provided by varying the power of Al magnetron source while power of Si source was constant. Three series of samples were deposited at different substrate temperatures. A sharp decrease in surface resistivity is observed while the Al content in the film changes smoothly. This result is explained by the segregation of Si and Al atoms due to Al diffusion during film deposition process.

For miniaturized vacuum-tube electron devices at millimeter and submillimeter (THz) bands, the possibility of low-voltage operation is of primary importance. Planar slow-wave structures (SWS) on dielectric substrates are favorable for the low-voltage operation. In this paper, we discuss design, fabrication and cold test of millimeter-wave planar SWSs. We consider the microstrip meander-line SWSs, which are designed for operation in traveling-wave tube power amplifiers with sheet electron beam.

Design and preliminary numerical simulations of D-band planar microstrip meander-line slow wave structure for lowvoltage tubes with sheet electron beam were carried out. An original approach based on magnetron sputtering and laser ablation methods was utilized for microstrip meander-line slow wave structure microfarication. An application of nanosecond and picosecond laser ablation for microfabrication of D-band (110-170 GHz) planar microstrip meander-line slow wave structure was considered. We have verified our original approach for planar slow wave structures microfabrication by using different CNC precision laser machines operating with different values of laser pulse duration (100 ns, 8 ns, 4 ns and 10 ps). Samples of slow wave structures were fabricated and characterized by scanning electron microscopy and profilometry methods. It was shown that each considered CNC precision laser machine allows fabricating D-band microstrip meander-line slow wave structure with required dimensions, but picosecond laser ablation has such advantages as the absence of ablation products (droplets, and etc.) on the slow wave structure surface. As the next step, we are going to study S-parameters of microfabricated D-band microstrip meander-line slow wave structure samples experimentally by using vector network analyzer with D-band frequency converters.

We consider the results of dielectric properties study in millimeter band of thin-films based on silicon nitride compositions. Silicon nitride thin-film coatings were deposited on a substrate by DC magnetron sputtering. As a substrate for silicon nitride thin-film coatings a quartz plate were utilized. The ratio of argon and nitrogen in the working gas mixture was chosen as the variable parameter to control the composition of the deposited thin-film coating. Several samples of silicon nitride thin-film coatings with about 1 um thickness were fabricated. Radiophysical and dielectric properties of the fabricated SiN-type thin-film coatings were studied in millimeter wave frequency band of 50-70 GHz (V-band) with help of free space measurement method. The obtained results have shown that by controlling the resistive thin-film coating composition one can only slightly vary the radiophysical and dielectric properties of coating in millimeter-band.

In this paper, we consider a short review of existing technologies of flexible antenna fabrication and propose our original approach for flexible antenna fabrication. Review of existing technologies of flexible antenna fabrication includes photolithography, screen printing, pad printing, gravure printing, inkjet printing, micro-dispensing, micro-jetting, and aerosol-jet technology. Advantages and disadvantages of each mentioned above technologies were noted. In the second part of this study, we consider our original technology for antenna fabrication on flexible substrates utilizing magnetron sputtering and laser ablation methods. Samples of flexible antennas are formed on a flexible dielectric substrate in a technology process comprising following basic stages: 1) deposition a conductive coating onto the dielectric substrate with help of magnetron sputtering, 2) formation the pattern of the antenna structure on the conductive coating by laser ablation. In the final stage, the substrate is divided into individual samples of specific sizes. A number of test flexible antennas fabricated by our original approach are shown.

Photoluminescent macroporous silicon is studied for tumor imaging application. Gamma-radiation is used for modification of morphology of pores and their size. It is shown by Raman and photoluminescence study that after the irradiation of gamma rays new nanocrystallites of smaller diameter in comparison to the initial porous silicon appeared.

The possibility of modifying the photoluminescence properties of porous silicon by irradiation with low doses of γ photons from a 226Ra radioisotope source and bremsstrahlung is demonstrated. The position of the longest photoluminescence wavelength tends to shift to the short-wavelength region of the spectrum. The emission efficiency increases upon irradiation of both the substrate and the layer formed.

A traveling wave tube amplifier (TWTa) operating in V-band (62–65 GHz) was designed considering a planar slow wave structure (SWS). Particle in cell simulations were performed to calculate the gain and the output power of the TWT. The simulated TWT showed a maximum gain of 36 dB at 64 GHz and an output power of 16 W. The planar SWS was then fabricated with a laser machining technique. S parameters measurements of the SWS showed excellent matching and low losses in the operating frequency band.

Here we report on experimental and numerical investigations of an electrodynamic structure assembled according to photonic crystals' principles placed inside a X-band rectangular waveguide which is promising for microwave electronics. The features of dispersion characteristics of photonic crystals can be used for efficient excitation of high-order (and, hence, high-frequency) electromagnetic modes. In this work, the electrodynamic structure is a2D array of thin metal pins. Transmission and reflection of proposed system were measured experimentally and evaluated numerically. The experimental results are in good agreement with the numerical ones.

We report the results of the design, simulation, fabrication, and cold-test measurements of millimeter-band 2D planar microstrip slow-wave structures (SWSs) on dielectric substrates. Such structures have a high slow-wave factor, which allows for low-voltage operation and reduction in the size and weight of the device. A low-cost and flexible fabrication technology based on magnetron sputtering and subsequent laser ablation has been developed and is reported in the paper. Microstrip meander-line SWS circuits at V-, W-, and D-bands have been fabricated and characterized. The fabrication of ring-bar planar SWSs by the photolithographic method is also discussed. Experimental measurement of S-parameters of the fabricated structures reveals good transmission properties. Return loss (S11) does not exceed −10 dB and attenuation is about 2 dB/cm in the V-band, 10 dB/cm in the W-band, and 8.5 dB/cm in the D-band.

The influence of low doses of γ rays on the capacitive properties of structures based on mesoporous silicon has been investigated. The concentration distribution of dangling charged bonds over the layer depth, which changes under irradiation, has been found using the capacitance–voltage characteristics at different frequencies of the test signal. It is shown that the concentration and relaxation time of surface charged states in a structure with a mesoporous silicon layer decrease under γ irradiation, which makes the material promising for devices with controlled reactance (varactors) that are resistant to γ irradiation.

Results of experimental studies on Si-W coatings fabrication by magnetron co-sputtering from two sources for electrodynamic structures in millimeter and submillimeter range of electromagnetic waves are presented. Control over sheet resistivity of the resulting coatings by varying the power of a magnetron with a tungsten target is demonstrated. Dependence of complex permittivity of Si-W coatings upon dielectric substrates on chemical composition in the frequency range of 50-70 GHz is studied.

A novel technology for microfabrication of millimeter-band planar microstrip slow-wave structures is considered. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a dielectric substrate. Then laser ablation is utilized to cut a slow wave structure from the copper layer. V-band (50–70 GHz) and W-band (75–110 GHz) meander-line slow wave structures are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed slow wave structures are studied by numerical simulation. Cold-test measurement are also carried out for microfabricated meander-line slow wave structures. The experimental results are in good agreement with the numerical ones. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications. The future work will be aimed to expansion of the proposed technology to manufacturing of higher-frequency E-band (110–170 GHz) planar slow wave structures.

We have proposed and developed an original approach for fabrication flexible antennas for biomedical application. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a flexible (polyimide) substrate. Then laser ablation is utilized to cut an antenna structure from the copper layer. For testing our approach we have chosen a number of examples of flexible antenna scheme with microstrip feeding structure working in ISM bands. A number of test flexible antennas were fabricated. Return loss (S11) of fabricated antennas were measured experimentally and calculated numerically. The obtained experimental results are in good agreement with the numerical ones. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications.

The study of the formation of silicon nanowhiskers by the method of non-current two-step etching is presented in this paper. Silicon nanowhiskers were obtained on unirradiated single-crystal silicon and on irradiated γ-quantum substrates. At an etching time of 20 to 50 minutes, the length of nanowhiskers is independent of the radiation dose (with a diameter of 70 to 140 nm), however, with increasing etching time, the length of the nanowhiskers increases sharply with increasing radiation dose. The optical and structural properties of silicon nanowhiskers under the influence of gamma irradiation are discussed.

Folded waveguide (FW) is a promising type of slow-wave structure (SWS) for millimeter-wave traveling-wave tubes. Results of development of several millimeter-band FW SWSs are presented. SWS circuits at Q- and V -band are fabricated by CNC-machining. Cold electromagnetic parameters of the SWS characteristics are simulated and reasonable agreement with the results of measurements is observed. Small-signal and large-signal gain is calculated.

Experimental studies were carried out by two different sources of gamma quanta. Samples were irradiated gamma - quantum radioisotope source 226Ra and electron accelerator braking gamma radiation - betatron Saratov state university. The form of the diffractograms shows the high crystallinity of the samples under study. The effect of gamma rays of radium led to a slight shift of the maximum of the reflex relative to the angle 2θ=29.18° to the left and a decrease in its width. The structure of the samples irradiated with γ-quanta of the bremsstrahlung of the betatron, according to the measurements, has undergone more significant and unexpected changes.

Microfabricated vacuum-tube millimeter- and THz-band sources are of great interest for numerous applications such as communications, radar, sensors, imaging, etc. Recently, miniaturized sheet-beam traveling-wave tubes for operation at sub-THz and THz bands have attracted a considerable interest. In this paper, we present the results of modeling and development of slow-wave structures (SWS) for medium power (10-100 W) traveling-wave tubes (TWT) amplifiers in near-THz frequency band. Different types of SWSs are considered, such as double-vane SWS for TWT with a sheet electron beam, folded-waveguide SWS, and novel planar SWSs on dielectric substrates.

A novel technology for microfabrication of millimeter and THz band planar microstrip slow-wave structures (SWS) is proposed. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a quartz substrate. Then laser ablation is utilized to fabricate a slow wave structure from the copper layer. V-band (50–70 GHz) meander-line SWSs were fabricated and characterized by scanning electron and optical microscopy. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications. The future work will be aimed to expansion of the proposed technology to manufacturing of higher-frequency W-band (75–110 GHz) and E-band (110–170 GHz) planar SWSs.

In this work we report the results of numerical simulation and cold-test measurements of electromagnetic parameters of the V-band (50–70 GHz) meander-line slow wave structure. The microstrip meander-line slow wave structure is suitable for using in a millimeter-band traveling wave tube amplifiers. Several samples of copper microstrip meander-line slow wave structure on a quartz substrate consisting of 50 meander periods with input and output couplers were designed and fabricated. The slow wave structure was microfabricated by using our original and novel technology for microfabrication. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a quartz substrate. Then laser ablation is utilized to cut a slow wave structure from the copper layer. This technique is a more facile, flexible and lower cost as compared to photolithography method. Transmission and reflection of microfabricated SWS were measured experimentally and calculated numerically. The results of the experimental cold-test measurements are verified by numerical simulations. Electromagnetic parameters of the slow wave structures were simulated using the finite-element ANSYS HFSS and COMSOL Multiphysics software packages. The results obtained with these two codes are in excellent agreement with each other and good agreement between experimental and numerical results is also observed.

The treatment with high frequency currents (HFC) is traditionally used to improve the mechanical properties of metal products, in particular hardness and wear resistance. A new method of carburization of titanium samples in a solid carburizer using HFC is proposed in the work. The temperature of the carburization is characterized by a wide range from 1000 to 1400 °C. As a result of thermochemical treatment, a hard coating of TiC (H ≥ 20 GPa) with a microstructure (d = 7-14 μm) consisting of nanoparticles (d = 10-12 nm) is formed on the titanium surface. These coatings are widely used in friction pairs for various purposes, including machinery, instrumentation and medicine.

The paper presents the method of tunneling microscopy study of mass transfer in the structure containing nanometer layer AgI. The possibility of using of interface Ag-AgI-insulator-metal as a resistive switching memory with charge ∼5 pC and multiplicity of resistance ∼20 is shown.

Electrical and photoelectric properties of porous silicon with introduced silver nanoparticles have been studied. It is shown that in the “dark–light–dark” operation mode, an abrupt jump of the dark current is observed upon illumination (with light spectrally close to sunlight), which is three to five times the initial dark current and the photocurrent. The voltages at which these abrupt changes in current are observed correspond to the range of existence of traps formed when the starting mesoporous silicon is obtained. It was found that the increased value of the dark current exhibits a long-term memory effect. The “current jump” can be attributed to the maximum capture of the generated photocarriers by traps, followed by their release in an electric field after the illumination.

A comparative study of the optical and morphological properties of different modifications of silicon and their dissolution upon interaction with distilled water and a biologically active medium is carried out. For the biologically active medium, nonpathogenic baker’s yeast (Saccharomycetes cereviseae) is chosen. It is shown that water and the biologically active medium interact with the surface of the materials and, thus, change the surface morphology and produce a modified layer. The strengths of the effect upon nanoparticles, nanoparticle-based structures (porous silicon), and single-crystal silicon doped with different types of impurities to different levels are different.

The effect of low exposure doses (5–40 kR) of gamma radiation on the electrical properties of structures based on a mesoporous silicon (SiMP) layer is investigated. It is demonstrated that the conductivity of the SiMP layer increases, the Fermi level shifts, and the trap density changes in gamma-irradiated Al/SiMP/p-Si/Al structures. Long-term stable switched-state memory in the region of the I–V curve hysteresis is revealed. This effect is controlled by the irradiation dose.

It was shown that the complex research of iron nanoparticles properties by different methods, supplemented each other, permit to receive the data about the interior sizes of nanoparticles, a number of physical properties of particles, their dependence on frequency and changes produced by various influences. It was found that the conductivity of nanoparticles changed under the square depen-dence σ = σoω2

The photoelectric and photovoltaic properties of structures based on mesoporous silicon passivated with iron (SiMP:Fe) are studied. It is shown that these properties ambiguously depend on the iron concentration. In the case of a sample with space-charge-limited currents (SCLCs), the charge-transport mechanism in the Al-SiMP:Fe-p-Si-Al heterostructure changes under illumination from the SCLC type to the barrier type. Passivation with 0.1–0.2 at % iron stabilizes not only the electrical, but also the photoelectric and photovoltaic properties of the structures. A further increase in the Fe concentration gives rise to new traps caused by the appearance of iron and silicon oxides, which leads to instability of the properties. The structures exhibit high sensitivity under low-level illumination. The open-circuit voltage is 16 mV under AM-1 irradiation (∼2 mW/cm2).

The current-voltage and capacitance-voltage characteristics of structures based on mesoporous silicon, obtained by electroless etching with passivation by iron, (SiMP:Fe) are investigated. It is shown that the conductivity and barriers in Al-SiMP:Fe-p-Si-Al heterostructures ambiguously depend on the Fe concentration. Passivation by iron changes not only the conductivity of the SiMP:Fe layer but also the character of carrier transport at low frequencies. At an iron concentration of ∼1 at % tunneling transport through barriers becomes dominant in comparison with jumps over dangling bonds. Passivation of the SiMP layer by iron stabilizes the SiMP electrical properties (which is confirmed by the values of the trap concentrations estimated from the current-voltage characteristic) of structures subjected to long-term storage. This is likely to be related to the interaction between iron ions and the silicon surface with the formation of oxides.

Developed luminescence method to study the growth mechanism of CuInS 2 quantum dots in real time is demonstrated.

Control methods of temperature fields inside a tissue during laser photothermolysis are an important point to develop biomedical applications of thermal destructions of cancer. One of the most promising approaches to measure and to control of temperature is the application of luminescence nanothermometers such as CuInS 2 nanoparticles. Temperature measurement can be carried out by determination of the maximum of the luminescence band. Thus, we have investigated the influence of exposure time and temperature on the position of the maximum of the luminescence band of CuInS 2 nanoparticles.

Manuscript is devoted to the comparison of CdSe/ZnS and CuInS2/ZnS quantum dots thermosensitivity in the view of their applications as nanothermometers. It was found the luminescence spectrum of CuInS2/ZnS quantum dots consists of two components, which are described by Gauss type functions and connected with different types of defects into nanoparticles. The heat treatments provide different effects such as spectral shifts, FWHM and amplitude for these too components. CdSe/ZnS nanoparticles spectra shifted to the red region; the average speed of spectrum shift is 0.065 nm per degree.