The main aim of this work was to perform low-temperature synthesis of glass-ceramics with YNbO4:Eu3+ crystallites and study the structural and luminescent properties of the samples synthesized. The inclusions crystallized in the ЅіО2–Na2О–K2O–Y2O3–Nb2O5–Eu2O3 (SiNaK) and B2O5–Na2О–Y2O3–Nb2O5–Eu2O3 (BNa) systems under the conditions of low-temperature synthesis were studied for the first time. It was shown that YNbO4:Eu3+ was crystallized in both systems under study. In the SiNaK system, SiO2 (quartz, cristobalite, and tridymite) was also crystallized under the chosen conditions. The BNa system was found to be most promising for the synthesis of doped glass-ceramics with YNbO4 because this system allows formation of only the desired crystallites. The luminescent properties of crystalline inclusions were studied by local cathodoluminescence. The glass-ceramics composition and structure were studied by X-ray spectral microanalysis and X-ray diffraction analysis.

The main aim of this work was to perform low-temperature synthesis of glass-ceramics with YNbO4 : Tb3+ crystalline inclusions and study the structural and luminescent properties of the samples synthesized. In the framework of this work, inclusions crystallized in the system B2O5-Na2O-Y2O3 -Nb2O5-Tb4O7 (Bura). It was shown that in this system, regardless of the precursors in the samples, YNbO4 : Tb3+ in an amount of more than 70% of the total crystalline component. The most promising system for the synthesis of activated glass-ceramics with YNbO4 proved to be synthesized from oxide precursors; it crystallized more than 95% YNbO4 : Tb3+ of the total crystalline component. The luminescent properties of crystalline inclusions were studied using the local cathodoluminescence method. The composition and structure of glass ceramics were studied by methods X-ray spectral microanalysis and X-ray diffraction phase analysis. Keywords: YNbO4 : Tb3+, luminescence, glass-ceramics.

Bulk β-Ga 2 O 3 samples grown by the Czochralski method are studied. Based on the studies of the absorbed current dynamics and the cathodoluminescence, it is shown that there is a localization of charges of both signs in the sample. The electron localization is demonstrated to lead to a substantial decrease in cathodoluminescence intensity.

The main purpose of this work was to carry out a low-temperature synthesis of glass ceramics containing YNbO4:Eu3+ crystallites and to study the structural and luminescent properties of the obtained samples. Within the framework of this work, the inclusions that crystallized under the conditions of low-temperature synthesis in the systems of SiO2-Na2O-K2O-Y2O3-Nb2O5-Eu2O3 (SiNaK) and B2O5-Na2O-Y2O3-Nb2O5-Eu2O3 (BNa) were investigated for the first time. It was shown that YNbO4: Eu3+ crystallized in both considered systems. In the SiNaK system the crystallization of SiO2 also occurred (quartz, crisstabolite, and tridymite) under the selected conditions. The BNa system proved to be the most promising for the synthesis of activated glass-ceramics with YNbO4, since the required crystallites crystallized only in ithis system. The luminescent properties of crystalline inclusions were investigated using the local cathodoluminescence technique. The composition and structure of glass ceramics were studied by electron-probe microanalysis and X-ray diffraction phase analysis.

Исследованы объемные образцы beta-Ga2O3, выращенные методом Чохральского. На основании исследований динамики поглощенного тока и катодолюминесценции было показано, что в образце наблюдается локализация заряда обоих знаков. Продемонстрировано, что локализация электронов приводит к существенному уменьшению интенсивности катодолюминесценции. Ключевые слова: объемный оксид галлия, люминесценция, ловушки носителей заряда.

Abstract The paper presents the results of a study of the effect of irradiation with heavy Ar ions on the structural and optical characteristics of 4H-SiC. It has been shown that as a result of already single irradiation with Ar ions with an energy of 53 MeV with a fluence of 1٠1010 cm-2, at least 2 powerful local regions with negative deformation prevail in the structure of silicon carbide. Along with this, a region with positive deformation is also observed in the structure. The formation of localized clusters with negative and positive deformations, along with the undisturbed matrix, is accompanied by the formation of linear type defects that partially relieve stresses in the structure. It is assumed that the resulting complex defect structure upon irradiation with Ar ions provides the effect of gettering of point defects and leads to the quantum efficiency of 4H-SiC UV photodetectors at the level of the initial samples.

The electronic structure of an ultra-thin molybdenum oxide film obtained by oxidation of molybdenum at an oxygen pressure of 1 Torr and the effect of adsorption of sodium atoms Na on its electronic structure are studied by ultra-vacuum photoelectron spectroscopy in ultrahigh vacuum. Photoemission spectra from the valence band and core levels of O 2s, Mo 3d Mo 3p, and Na 1p are studied, upon synchrotron excitation in the photon energy range 80 − 600 eV. It is shown that in the formed oxide film, molybdenum is in two states: Mo6+ and Mo4+. On the surface of the oxide, oxygen is induced both in the composition of the oxides and in hydroxyl. It was shown that MoO3 is formed on the surface, and MoO2 at a distance from the surface. The deposition of Na atoms leads to intercalation of the molybdenum oxide layer.

The results of investigations of initial n-4H–SiC structures by various methods are presented. The structures represent a highly doped n+ substrate with epitaxial layers 5 μm thick grown by chemical vapor deposition (CVD). The concentration of uncompensated donors in the epitaxial layer is in the range of Nd – Na = (1–50) × 1014 cm–3. Using the results of X-ray diffraction analysis, it is found that, in order to obtain efficient 4H–SiC ultraviolet photodetectors, it is desirable to have structures of epitaxial layers in which the effect of point-defect gettering, leading to an increase in the lifetime of charge carriers and in the values of quantum efficiency, is observed. The photosensitivity of the investigated samples significantly depends on the degree of imperfection of the CVD epitaxial layer, which results in a change in the lifetime of charge carriers and, as a consequence, in a change in the quantum efficiency of 4H–SiC ultraviolet photodetectors.

The influence exerted by the carrier concentration in the range (1–50) × 1014 cm–3 in n-4H-SiC chemical-vapor deposited (CVD) epitaxial layers on the spectral characteristics of UV photodetectors with Cr Schottky barriers in the range of 200–400 nm is revealed and explained in terms of the photoconductivity theory. Schottky barriers with a Cr film thickness of 20 nm and diameter of 8 mm are formed by thermal evaporation in vacuum through masks. A noticeable effect of the carrier concentration in the CVD epitaxial layers on the spectral characteristics of photodetectors upon heating to 200°C is also observed and accounted for by a difference between the generation-recombination processes. The irradiation of photodetectors with 15-MeV protons at a fluence of 4 × 1012 cm–2 and a temperature of 200°C leads to an increase in the quantum efficiency as compared to samples irradiated in similar modes at 25°C. This is indicative of an increase in the radiation hardness and service life of 4H-SiC devices at elevated temperatures.

The work was aimed at development of glasses for encapsulation of self-glowing crystals, doped with alpha radionuclides. Bismuth borosilicate-based glass systems doped with Eu3+, B2O3-SiO2-Al2O3-Bi2O3-MO (where M = Ba, Sr and Zn) (Si-Bi -x), with various concentrations of activator were studied. The optimal synthesis conditions were selected, the composition of the obtained glasses was investigated using electron-probe microanalysis technique. Optical properties of glasses were investigated using the following methods - cathodoluminescence, photoluminescence and absorption. The range of the optimal activator concentration was determined.

The results of a study into the effect of irradiation with heavy Ar ions on the structural and optical characteristics of 4H-SiC are presented. It is shown that even upon single-time irradiation with 53-MeV Ar ions at a fluence of 1 × 1010 cm–2 there are at least two powerful local regions with negative deformation dominant in the structure of silicon carbide. Also, a region with positive deformation is observed in the structure. The formation of localized clusters with negative and positive deformations along with the undisturbed matrix gives rise to linear-type defects that partially relieve stresses in the structure. It is assumed that, upon irradiation with Ar ions, the resulting complex defect structure provides the effect of point-defect gettering and leads to a quantum efficiency of 4H-SiC UV photodetectors that is comparable with that of the initial samples.

Представлены результаты исследования различными методиками исходных структур n-4H-SiC, представляющих высоколегированную n+-подложку с выращенным химическим осаждением из газовой фазы эпитаксиальным слоем толщиной 5 мкм. Концентрация носителей заряда в эпитаксиальном слое в диапазоне Nd-Na=(1-50)·1014 см-3. Привлекая результаты рентгеноструктурного анализа, было установлено, что для получения эффективных 4H-SiC ультрафиолетовых фотоприемников желательно иметь структуры эпитаксиальных слоев, в которых наблюдается эффект геттерирования точечных дефектов, что приводит к росту времени жизни носителей заряда и увеличению значений квантовой эффективности. Фоточувствительность исследованных образцов значительно зависит от степени дефектности в CVD эпитаксиальном слое, приводящей к изменению времени жизни носителей заряда и, как следствие, к изменению квантовой эффективности 4H-SiC ультрафиолетовых фотоприемников. Ключевые слова: карбид кремния, рентгеноструктурный анализ, эффект геттерирования, квантовая эффективность.

Abstract The influence exerted by the carrier concentration in the range (1–50) × 10^14 cm^–3 in n -4 H -SiC chemical-vapor deposited (CVD) epitaxial layers on the spectral characteristics of UV photodetectors with Cr Schottky barriers in the range of 200–400 nm is revealed and explained in terms of the photoconductivity theory. Schottky barriers with a Cr film thickness of 20 nm and diameter of 8 mm are formed by thermal evaporation in vacuum through masks. A noticeable effect of the carrier concentration in the CVD epitaxial layers on the spectral characteristics of photodetectors upon heating to 200°C is also observed and accounted for by a difference between the generation-recombination processes. The irradiation of photodetectors with 15-MeV protons at a fluence of 4 × 10^12 cm^–2 and a temperature of 200°C leads to an increase in the quantum efficiency as compared to samples irradiated in similar modes at 25°C. This is indicative of an increase in the radiation hardness and service life of 4 H -SiC devices at elevated temperatures.

The electronic structure of gold nanoparticles deposited on the surface of tungsten before and after the adsorption of sodium atoms followed by heating at T = 630 K was studied in situ in ultrahigh vacuum by photoelectron spectroscopy. The photoemission spectra from the valence band and core levels of Au 4f and Na 2p were studied under synchrotron excitation in the photon energy range 80-600 eV. It was shown that changes in the spectra of the valence band and core levels of Au 4f and Na 2p are associated with a change in the surface topography caused by the adsorption of sodium atoms and heating, which led to an increase in the surface area by several times. The surface topography and cathodoluminescence of a layer of gold nanoparticles deposited on a tungsten surface are studied

The electronic structure of an ultra-thin molybdenum oxide film obtained by oxidation of molybdenum at an oxygen pressure of 1 Torr and the effect of adsorption of sodium atoms on its electronic structure are studied by photoelectron spectroscopy. Photoemission spectra from the valence band and core levels of O 2s, Mo 3d, Mo 3p, and Na 1p are studied upon synchrotron excitation in the photon energy range 80–600 eV. It is shown that in the formed oxide film, molybdenum is in two states: Mo6+ and Mo4+. On the surface of the oxide, oxygen is induced both in the composition of the oxides and in hydroxyl. It was shown that MoO3 is formed on the surface, and MoO2 at a distance from the surface. The deposition of Na atoms leads to intercalation of the molybdenum oxide layer.

Electronic structure of molybdenum oxides obtained by the oxidation of molybdenum at an oxygen pressure of 1 Torr (thin film) and air (thick film) was studied. It was shown that a thick oxide film is formed from MoO3 oxide, and a thin film from a mixture of MoO3 and MoO2 oxides, which is reflected in the form of valence band spectra. Oxygen on the surface belongs both in molybdenum oxide and in the hydroxyl group, which is associated with dissociative adsorption of water during the oxidation of molybdenum in air for a thick film.

We studied the electronic structure of gold nanoparticles deposited on a tungsten surface before and after the deposition of sodium atoms with subsequent heating at T = 630 K by in situ photoelectron spectroscopy in ultrahigh vacuum. The photoemission spectra from the valence band and core levels of Au 4f and Na 2p were studied upon synchrotron excitation in the photon energy range of 80–600 eV. The changes in the spectra of the valence band and core levels of Au 4f and Na 2p are associated with a change in the surface topography caused by the deposition of sodium atoms and heating, which led to an increase in the surface area by several times. The surface topography and cathodoluminescence of a layer of gold nanoparticles deposited on a tungsten surface are studied.

In this study we related structural properties of GaN grown on ceramic substrate and studied with transmission electron microscopy with the results of photo-and cathodoluminescence investigations. We found that stacking faults in the basal plane were responsible for both strong room temperature visible emission and exciton-related ultraviolet luminescence at cryogenic temperature.

In situ photoelectron spectroscopy studies in ultrahigh vacuum of the electronic structure of the surface of molybdenum oxidized in air and during the adsorption of sodium Na with submonolayer coatings were carried out. The spectra of photoemission from the valence band and the core levels O 1s, O 2s, Mo 4s and Na 2p were studied under synchrotron excitation in the photon energy range of 80 – 600 eV. The change in the spectrum of the oxygen core levels associated with the substitution of hydrogen atoms in the hydroxyl group by sodium atoms was found. The surface topography and cathodoluminescence of molybdenum oxide were studied.

In the study of materials on electron probe devices in the field of action of the electron beam, a contaminating hydrocarbon film is formed, which affects the experimental results. In this paper, we have studied the influence of a contamination film on carbon-film-coated dielectrics on the intensity of cathodoluminescence and characteristic X-ray lines. The absorption coefficient of the contamination film in the visible and UV ranges has been determined. Filming mechanisms at different parameters of the electron beam have been discussed.