The spectra of anticrossing of spin sublevels have been recorded and spin-3/2 color centers have been identified for the first time in commercially available 4H-SiC Schottky diodes irradiated with 0.9-MeV electrons or 15-MeV protons. The effect of the irradiation density on the defect formation has been shown. It has been demonstrated that the increase in the temperature at which proton irradiation is carried out acts as a short-term annealing, leading to a decrease in the concentration of point defects.

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.

In two-dimensional (2D) transition metal dichalcogenides, the sequence and splitting energy between spin-allowed (bright) and spin-forbidden (dark) excitons controls the optical and transport properties. In this paper, we discuss the effect of strain at both compression and tension on the band structure and fine spectrum of exciton states in MoS 2 nanostructures. Using a combination of micro-Raman and time-resolved micro-photoluminescence, we found that the exciton spectrum in unstrained layers in complete agreement with the theoretical predictions. In the A-exciton series, the bright state is the lowest in the monolayer, while in the bilayer the exciton states are spin-degenerate due to the even number of layers. However, strain can lift the degeneracy and increase the splitting value in the monolayer by several times. On folds subjected to local tension, the splitting decreases down to the reversed sequence of dark and bright excitons. With both types of strain, the band structure tends to transform towards the indirect type.

Technology of obtaining graphene by means of ultrasonic dispersion of thermally expanded graphite in the presence of a surface-active polymer Nafion is presented. The technology makes it possible to obtain large amounts of low-layer (1-3 layers) graphene in a relatively short time. An approach to control the dispersion process based on UV spectroscopy of dispersions is described. A mechanism is proposed for the effect of a surface-active polymer on the production of low-layer graphene by ultrasonic dispersion.

The anti-Stokes luminescence of perovskite CsPbBr3 nanocrystals in a fluorophosphate glass matrix has been detected and experimentally studied upon optical excitation to the low-energy edge of the photoluminescence band. The intensity of anti-Stokes luminescence depends linearly on the pump power and increases rapidly with increasing temperature. A simple three-level model is proposed. It well describes the main regularities of the observed phenomenon.

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.

We analyze the synthesis of the buffer carbon layer on a SiC(0001) single crystal and its subsequent intercalation with cobalt atoms. It is shown using X-ray photoelectron spectroscopy that the intercalation is accompanied with the formation of a surface cobalt silicide alloy under the quasi-free graphene. The data measured using angle-resolved photoelectron spectroscopy demonstrate the presence of a Dirac cone near the Fermi level, which confirms the formation of quasi-free graphene as a result of intercalation. The morphology and homogeneity of the resulting system have been investigated using atomic force microscopy and Raman spectroscopy. The features of the graphene band structure on possible cobalt silicide alloys have been investigated using the density functional theory. The calculations of the chemical shift of the 2p level of Si for cobalt silicides confirm the presence of CoSi and CoSi2 components in X-ray photoelectron spectroscopy data. It is shown that the formation of quasi-free graphene with a linear dispersion of the π states is possible only on the CoSi surface. In view of the importance of investigation of graphene on insulating substrates as well as unique properties of graphene in contact with magnetic metals, we hope that this study will make a contribution to further realization of graphene in spintronics and nanoelectronics devices.

Heavily doped 3C-SiC films based on semi-insulating 6H-SiC substrates were obtained by sublimation epitaxy. The structural perfection of the obtained samples was monitored by X-ray diffractometry. The measurements of the photoluminescence and Hall effect spectra have confirmed the rather high perfection of the obtained epitaxial layers.

Heavily doped 3C-SiC films based on semi-insulating 6H-SiC substrates were obtained by sublimation epitaxy. The structural perfection of the obtained samples was monitored by X-ray diffractometry. The measurements of the photoluminescence and Hall effect spectra have confirmed the rather high perfection of the obtained epitaxial layers.

The formation of iron silicide thin films under graphene grown on the silicon carbide surface is investigated. The thin films are synthesized by consecutive intercalation of iron and silicon atoms into the graphene. Experiments are carried out in situ in ultrahigh vacuum. The elemental composition and chemical state of the surface of prepared samples and their atomic structure are determined by low-energy electron diffraction and high-resolution X-ray photoelectron spectroscopy using synchrotron radiation. The thickness of deposited iron and silicon layers varies in the range of 0.1–2 nm, and the sample annealing temperature is varied from room temperature to 600°C. We show that intercalation of silicon into the graphene/Fe/SiC system leads to the formation of a layer of Fe–Si solid solution coated with the surface silicide Fe3Si. The films are effectively protected by graphene from exposure to ambient environment, which opens possibilities for their practical application.

The paper presents the results of experiments in the fabrication and research of properties of photodetector structures on the basis of monolayer graphene produced by chemical vapor deposition. The base structure was the geometry of a Ta2O5 vertical microcavity with a lower dielectric SiO2/Ta2O5 distributed Bragg reflector with a resonance wavelength of about 850 nm. The conditions were optimized for the transfer and fabrication of mesas in the graphene layer on the microcavity surface. The diagnostics of the structural quality of graphene after the fabrication of mesas in the graphene layer and contact pads by Raman spectroscopy evidence the monolayer structure of graphene with a low singularity strength in its spectrum that is responsible for the structure imperfection. The photocurrent value at local optical pumping was measured.

The process of formation of cobalt silicides near the graphene-silicon carbide interface by intercalation of single-layer graphene grown on the 4 H - and 6 H -SiC(0001) polytypes with cobalt and silicon is studied. The experiments were carried out in situ in ultrahigh vacuum. The analysis of the samples is performed by high-energy-resolution photoelectron spectroscopy using synchrotron radiation, low-energy electron diffraction, and also Raman spectroscopy, atomic-force and kelvin-probe microscopies. The thicknesses of the deposited cobalt and silicon layers is varied to 2 nm, and the sample temperature, from room temperature to 1000°C. Co and Si atoms deposited on heated samples is found to penetrate under graphene and are localized between the buffer layer and the substrate, which leads to a transformation of the buffer layer into additional graphene layer. It is shown that the result of intercalation of the system with cobalt and silicon is the formation under two-layer graphene of a Co–Si solid solution and silicide CoSi coated by the surface Co 3 Si phase. It is shown that the thickness and the composition of the formed silicide films can be changed by varying the amount of the intercalated material and the order of their depositions.

Исследован процесс формирования тонких пленок силицидов железа под графеном, выращенным на поверхности карбида кремния, путем последовательного интеркалирования графена атомами железа и кремния. Эксперименты проводились in situ в условиях сверхвысокого вакуума. Элементный состав и химическое состояние поверхности образцов, а также их атомная структура контролировались с помощью фотоэлектронной спектроскопии высокого энергетического разрешения с использованием синхротронного излучения и дифракции медленных электронов. Толщина нанесенных слоев железа и кремния варьировалась в диапазоне 0.1-2 nm, а температура отжига образцов изменялась от комнатной до 600oС. Показано, что интеркалирование системы графен/Fe/SiC кремнием приводит к образованию слоя твердого раствора Fe-Si, покрытого поверхностным силицидом Fe3Si. Полученные пленки надежно защищены графеном от воздействия окружающей среды, что открывает возможности для их практического применения. Ключевые слова: графен на карбиде кремния, железо, интеркалирование, силициды, фотоэлектронная спектроскопия.

Abstract The process of formation of cobalt silicides near the graphene-silicon carbide interface by intercalation of single-layer graphene grown on the 4 H - and 6 H -SiC(0001) polytypes with cobalt and silicon is studied. The experiments were carried out in situ in ultrahigh vacuum. The analysis of the samples is performed by high-energy-resolution photoelectron spectroscopy using synchrotron radiation, low-energy electron diffraction, and also Raman spectroscopy, atomic-force and kelvin-probe microscopies. The thicknesses of the deposited cobalt and silicon layers is varied to 2 nm, and the sample temperature, from room temperature to 1000°C. Co and Si atoms deposited on heated samples is found to penetrate under graphene and are localized between the buffer layer and the substrate, which leads to a transformation of the buffer layer into additional graphene layer. It is shown that the result of intercalation of the system with cobalt and silicon is the formation under two-layer graphene of a Co–Si solid solution and silicide CoSi coated by the surface Co_3Si phase. It is shown that the thickness and the composition of the formed silicide films can be changed by varying the amount of the intercalated material and the order of their depositions.