Thin conductive films deposited on the surface of the heat-sensitive element of the radiation receiver make it possible to absorb up to 50% of the incident radiation. This increases the efficacy of detectors in the terahertz (THz) frequency range. The absorbing conductive coating on the array of a multi-pixel detector is an ordered structure with dimensions comparable to the wavelength of THz radiation. Diffraction of radiation on this structure leads to a change in the wavefront of both transmitted and reflected waves, leading to image distortion in a multi-pixel detector. Based on experimental data obtained using pulsed THz and IR Fourier spectroscopy, the transmission and conductivity spectra of solid films and capacitive Al meshes of different thicknesses were analyzed. The optimal thickness of the Al coating for maximum absorption of THz radiation has been determined. The transmission spectra of capacitive grids with an Al film thickness corresponding to the maximum absorption indicate the disappearance of diffraction effects in the THz range.

Imprinting magnetism into graphene makes an important step to its applications in spintronics. An actively explored approach is proximity coupling of graphene to a 2D magnet. In these endeavors, the use of epitaxial graphene may bring significant advantages due to its superiority over the exfoliated counterpart and natural integration with the substrate but the problem of attaining magnetism persists. Here, we report synthesis and analysis of a heterostructure coupling epitaxial graphene with a regular lattice of magnetic atoms formed by Eu intercalation. The magnetization measurements reveal easy-plane 2D magnetism in the material, with the transition temperature controlled by low magnetic fields. The emerging negative magnetoresistance and anomalous Hall effect point at spin polarization of the carriers in graphene. In the paramagnetic phase, the magnetoresistance in graphene exhibits critical exponential behavior of the induced magnetic state. The intercalation does not compromise the parental electronic structure - quantum oscillations in the resistivity manifest low-mass carriers in graphene. The results are set against those for an isostructural material based on intercalated nonmagnetic Sr. Overall, the study expands the family of 2D magnets and establishes a prospective material for graphene-based spintronics.

An approach of direct bonding of SiC wafers of differing polytypes has been implemented in order to create a template for cubic 3C-SiC homo epitaxy. Hetero epitaxial 3C-SiC layers grown by chemical vapor deposition were transferred onto a hexagonal 6H-SiC wafer. The results of structural characterization showed that the quality of 3C-SiC sublimation epitaxy on the templates is comparable to the level of epitaxy of cubic silicon carbide by chemical vapor deposition method. It was confirmed that the 3C-SiC layer transferred onto the 6H-SiC substrate plays the role of a crystalline “seed” that determines cubic polytype of the overgrown SiC layer.

THz technologies developments into practice are limited by the absence of commercially available THz endoscopic systems. Previously, the transmission properties of waveguides, fibers and even fiber bundles based on shaped sapphire were studied. Sapphire hollow-core waveguides are suitable for efficient radiation transmission with minimal losses and for applications in endoscopy of hard-to-access objects and highresolution imaging.

Objective. To develop technique immobilizing antibodies graphene surface of proteins that play a significant role in pathogenesis Alzheimer's disease.Materials and methods. Graphene films were obtained sublimation surface of SiC substrates. Presence graphene monolayer was confirmed spectroscopy spectra. Graphene surface quality was evaluated cyclic voltammetry. Functionalization by amino groups was carried out method based on sorption pyrene derivatives from a solution and phenylnitrogroups electrochemical method. Graphene was kept in solutions monoclonal antibodies to human beta-amyloid peptide 1–42. Preparations were also kept in solution secondary antibodies labeled with FITZ. Results were evaluated fluorescence microscopy. Additionally, samples were kept in solution antibody with peroxidase label, which was detected chemiluminescence.Results. For attachment specific antibodies surface of graphene, quality its surface is great importance. Optimal working concentration of antibodies of human beta-amyloid 1–42 in solution for subsequent manufacture biological sensors is 15 micrograms per 1 ml. Covalent crosslinking antibodies with glutaraldehyde with amino groups on graphene gives a slight gain in the level fluorescence compared with noncovalent sorption on graphene with nitro groups. Functionalization phenylnitrogroups is optimal for further work related to the identification specific antigens.Conclusions. The technique of immobilization on the graphene surface of specific antibodies to beta-amyloid in concentrations detected by fluorescence microscopy and chemiluminescence is investigated. Amount antibodies sufficient to create a biosensor is immobilized on graphene. It was found that functionalization of phenylnitrogroups allows creating optimal conditions for the attachment of antibodies to the graphene surface, as well as washing resulting antibody-antigenic complexes for further reuse of graphene biosensors.

While terahertz (THz) technology offers a variety of applications in medical diagnosis, nondestructive testing, and quality control, its acceptance in these practical fields is hampered by the absence of endoscopic systems, capable of sensing the complex refractive index of the hard-to-access objects. In this paper, we develop the THz endoscope based on the hollow-core antiresonant waveguide, formed by a polytetrafluoroethylene (PTFE)-coated sapphire tube with the outer end closed by a monolithic sapphire window. The endoscope is attached to the backward wave oscillator spectrometer to measure the sample reflectivity. By studying the well-known liquid and solid samples, we demonstrate that analysis of the Fabry–Pérot resonance in the measured reflection spectra makes it possible to quantify the complex refractive index of an analyte. Thanks to the advanced chemical inertness and thermal strength of sapphire and PTFE, the developed endoscope is capable of operation in harsh environments, which broadens the range of its applications. Our findings pave the way for the THz technology use in a number of demanding practical fields.

The properties of graphene chips with low reproducibility (LR) after photolithography (PLG) and graphene functionalization have been studied. It is shown that the introduction of additional cleaning after PLG can significantly increase the reproducibility of the parameters of processed graphene in biosensors. The use of dilute PBS solutions for virus detection makes it possible to increase the relative concentration sensitivity of biosensors by several times.

The simulation results of the temperature distribution in the growth area of graphene layers obtained by the method of thermal decomposition of the silicon carbide surface substrates in setup with induction heating are presented. The heating parameters of the setup elements are calculated using the commercial package COMSOL Multiphysics taking into account the electrical, thermal and magnetic properties of the materials from which the growth plant elements are made. A numerical estimate of the heating inhomogeneity of silicon carbide plates over its area during the growth of graphene layers at a given temperature is given. It is shown that the lateral temperature distribution over the area of the plate has radial symmetry with decreasing values towards the center.

BSTS epitaxial thin film topological insulators were grown using the MBE technique on two different types of substrates i.e., Si (111) and SiC/graphene with Bi0.7Sb1.6Te1.8Se0.9 and Bi0.9Sb1.5Te1.8Se1.1, respectively. The crystallographic properties of BSTS films were investigated via X-ray diffraction, which showed the strongest reflections from the (0 0 l) facets corresponding to the rhombohedral phase. Superior epitaxial growth, homogeneous thickness, smooth surfaces, and larger unit cell parameters were observed for the films grown on the Si substrate. Polarization dependent Raman spectroscopy showed a weak appearance of the A(g) mode in cross--polarized geometry. In contrast, a strong E-g mode was observed in both parallel and cross-polarized geometries which correspond to the rhombohedral crystal symmetry of BSTS films. A redshift of A(g) and E-g modes was observed in the Raman spectra of BSTS films grown on the Si substrate, compared to those on SiC/graphene, which was directly associated with the unit cell parameter and composition of the films. Raman spectra showed four fundamental modes with asymmetric line shape, and deconvolution of the peaks resulted in additional modes in both the BSTS thin films. The sum of relative ratios of linewidths of fundamental modes (A(g) and E-g) of BSTS films grown on Si substrate was lower, indicating a more ordered structure with lower contribution of defects as compared to BSTS film grown on SiC/graphene substrate.

A structural study of the transformation of 6√3 reconstruction on the surface of a 4H–SiC substrate into quasi-free epitaxial graphene was carried out by the reflection high-energy electron diffraction (RHEED) method. The conversion was carried out via hydrogen intercalation between the reconstructed layer and the adjacent top layer of SiC. The initial 6√3 reconstruction was obtained during short sublimation annealing of the 4H–SiC substrate in an argon medium. A slight violation of the 6√3 reconstruction layer formation uniformity was found. The results of the study of the crystal structure of quasi-free-standing graphene and single-layer graphene comprising a buffer layer formed on 4H–SiC in the traditional way in an Ar atmosphere without intercalation were compared.

The well-known effect of the local interaction between graphene and photoresist (LIGF) during the creation of biosensors is shown to lead to non-uniform distribution of compressive stresses, which deteriorates the adsorption properties of graphene, parameter reproducibility, and detecting ability of influenza B and SARS-Cov-2 biosensors. It is also shown that controlling the occurrence of LIGF areas on a graphene surface by atomic force microscopy or introducing a protective layer between graphene and photoresist can minimize the non-persistent effect of LIGF. The results of influenza B and SARS-CoV-2 imaging on the graphene surface in biosensor chips in a scanning electron microscope are presented.

At present, intensive research is underway in the field of vacuum-sublimation growth of 3C-SiC. Transfer of a thin (001)3C-SiC layer onto a 6H-SiC wafer is a promising way to fabricate a 3C-SiC/6H-SiC substrate for growing device-quality homoepitaxial films of low defect density. The article presents the results of the structural characterization of an interface formed during the transfer of a 3C-SiC layer onto a 6H-SiC(0001) wafer, performed with transmission electron microscopy (TEM). A 3C-SiC film with a thickness of about 10 mu m, grown by chemical vapor deposition (CVD) on a Si(001) substrate, was utilized in the study. Silicon acted as a bonding material in the transfer process. The morphology and microstructure of the interface between a 6H-SiC substrate and a 3C-SiC (001)-oriented layer are under consideration. TEM investigation reveals an effect of "self"-orientation of the layer with respect to the wafer during the transfer process: an interaction between the molten silicon layer and silicon carbide throughout crystallization results in the generation of defined orientation relationships with respect to substrate axes. An analysis of selected area electron diffraction patterns taken from interfaces showed the relationships to be 3C-SiC{001} & Vert; 6H-SiC(0001) and 3C-SiC < 11((sic)) 0 > similar to & Vert; 6H-SiC < 11 2((sic))0 >.

Chemical composition and electronic structure of the native-oxide-covered Al x Ga 1- x As(100) ( x - 0.3) surfaces were investigated by x-ray photoelectron spectroscopy and photoluminescence before and after treatment at room temperature with a concentrated aqueous solution of sodium sulfide in order to get inside into mechanism of sulfide solution interaction with aluminum-containing III-V alloys. Even short treatment of the n-AlGaAs(100) surface leads to the removal of the most of the native oxide layer so that the surface is covered with a thin layer of residual aluminum and gallium oxides with a thickness of approximately 1 ML, which can be formed during air exposure after termination of the chemical treatment. Longer treatment of the n -AlGaAs(100) surface does not further reduce the amount of residual aluminum and gallium oxides. The etching of native oxide layer on the p-AlGaAs(100) surface proceeds slower and the lowest amount of residual aluminum and gallium oxides is achieved after etching for 12 min. At the same time sulfur is hardly adsorbed at the AlGaAs(100) surfaces after interaction with the solution. It is found that the lower the amount of residual aluminum and gallium oxides on n- and p-AlGaAs(100) surfaces, the higher is the photoluminescence intensity. The band bending on the native-oxide-covered n- and p-AlGaAs(100) surfaces is about 0.85 and 0.5 eV, respectively, while the ionization energy is nearly the same for both surfaces. Treatment of n- and p-AlGaAs(100) surfaces with an aqueous sodium sulfide solution causes simultaneous decrease in their ionization energy.

The quality of graphene intended for use in biosensors was assessed on manufactured chips using a set of methods including atomic force microscopy (AFM), Raman spectroscopy, and low-frequency noise investigation. It is shown that local areas of residues on the graphene surface, formed as a result of the interaction of graphene with a photoresist at the initial stage of chip development, led to a spread of chip resistance (R) in the range of 1–10 kOhm and to an increase in the root mean square (RMS) roughness up to 10 times, which can significantly worsen the reproducibility of the parameters of graphene chips for biosensor applications. It was observed that the control of the photoresist residues after photolithography (PLG) using AFM and subsequent additional cleaning reduced the spread of R values in chips to 1–1.6 kOhm and obtained an RMS roughness similar to the roughness in the graphene film before PLG. Monitoring of the spectral density of low-frequency voltage fluctuation (SU), which provides integral information about the system of defects and quality of the material, makes it possible to identify chips with low graphene quality and with inhomogeneously distributed areas of compressive stresses by the type of frequency dependence SU(f).

Предложен метод определения аппаратной функции при измерениях поверхностного потенциала в режиме Кельвин-зонд-микроскопии. Метод основан на применении в качестве тестовой структуры поверхности политипов SiC, содержащих области однослойного и двухслойного графена. Измерение профилей потенциала вдоль различных направлений на такой поверхности позволяет определить аппаратную функцию для зондовых измерений потенциала. Используя аппаратную функцию, можно выполнять процедуру деконволюции и восстанавливать точный потенциал поверхности. Ключевые слова: сканирующая зондовая микроскопия, Кельвин-зонд-микроскопия, потенциал поверхности, тестовые структуры, графен, карбид кремния.

This paper reports on the development of direct bonding of 3C-SiC epitaxial lay-ers grown by chemical vapor deposition on silicon substrates and 6H-SiC single crystal wafers. It has been found that the bonding temperature is a critical parameter to obtain mechanical contact between the transferred 3C-SiC layers and the 6H-SiC carrier plates. The results of structural characterization showed that the structure of epitaxial layers grown by sublimation on bonded substrates corresponds to a pure cubic phase of high quality.

Direct laser writing/ultra-hyperdoping technology was harnessed to fabricate a universal CMOS-compatible Si-based broadband (UV-THz) n-p junction detector, with its spectral response controlled by external liquid helium-nitrogen cooling. Near-far IR (2-40 mu m) temperature-dependent photoconductivity (PC) was revealed in a biased n-p junction, made of n-type sulfur-ultrahyperdoped Si (uh-Si, sulfur content similar to 1 at. %) sub-micron-thick layer on a surface of a p-doped Si substrate. The observed broadband photoconductivity is provided by a dense quasi-continuum series of sulfur-impurity donor states near the conduction band bottom (so-called "intermediate band", the bandwidth approximate to 0.6 eV), corresponding to IR-absorbing neutral and singly-ionized substitutional atomic and cluster centers of sulfur. The "intermediate" donor band supports the gradual "blue" spectral migration of PC maximum due to thermal ionization of deeper states at the temperature increasing in the range of 5-250 K. As a result, in the temperature range of 77-300 K complementary THz (wavenumbers <100 cm(-1)) spectroscopy indicates the predominating Drude-like conduction-band response of electrons and their gradually raising density similar to 10(19)-10(20) cm(-3). Illustrating the thermal-ionization depletion of the donor sulfur states from the THz-probed plasma side, this unveils the unprecedently high concentration of electrically-active donor sulfur centers similar to 10(20) cm 3 and related donor-state density similar to 10(20) states/eV.cm(3) in the uh-Si sample. Overall, these advances enable in situ laser writing of universal liquid helium/nitrogen cooled Si nano/micro/macrodetectors with broad - near-far IR and even THz - spectral response, crucial for photovoltaics, thermal and bio-imaging.

This paper presents the results of a study of the effect of external influences on the structure and phase composition of porous SiC layers obtained by anodization. It is shown how carrying out of standard technological operations makes it possible to control the properties of porous structures and significantly expands the variety of their morphological forms. The con-ditions facilitating the occurrence of phase-structural and polytype transformations in porous SiC structures are determined.

The basic mechanisms of absorption of THz range radiation in optically perfect LiGdF4 single crystals were studied using the broadband experimental data and the dielectric response function analysis within the harmonic oscillator model. The polarized IR reflection spectra have allowed one to determine the phonon contribution in the absorption coefficient in the THz range, while transmission spectra in the THz range were used to obtain the birefringence value and the effects of various mulitparticle processes. Additionally, we established the optical and electrodynamic parameters of the LiGdF4 single crystal, which are necessary for the design of nonlinear optical devices.

Hysteresis response of epitaxially grown graphene nanoribbons devices on semi-insulating 4H-SiC in the armchair and zigzag directions is evaluated and studied. The influence of the orientation of fabrication and dimensions of graphene nanoribbons on the hysteresis effect reveals the metallic and semiconducting nature graphene nanoribbons. The hysteresis response of armchair based graphene nanoribbon side gate and top gated devices implies the influence of gate field electric strength and the contribution of surface traps, adsorbents, and initial defects on graphene as the primary sources of hysteresis. Additionally, passivation with AlO x and top gate modulation decreased the hysteresis and improved the current-voltage characteristics.