Anatoli Popov

Anatoli Popov
Institute of Solid State Physics University of Latvia

PhD Dr Phys

About

283
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Introduction
Senior scientist at the Institute of Solid State Physics, University of Latvia

Publications

Publications (283)
Article
The optical spectra of a single crystal of α-Al2O3Cr³⁺ were studied in a wide temperature range. The crystal was demonstrated to have a potential for optical thermometric applications. Three ways of measuring temperature were tested and analyzed: i) luminescence intensity ratio of the R1 and R2 lines; ii) change of the full width of half maxima of...
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We computed, at the ab initio level, BaZrO 3 , CaTiO 3 , SrTiO 3 as well as WO 3 and ReO 3 (001) surfaces and analyzed systematic tendencies therein. As obtained by our ab initio hybrid DFT-HF computations, at BO 2-terminated (001) surfaces of investigated ABO 3 perovskites as well as WO 3 and ReO 3 oxides, all top-layer ions shift in the direction...
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This article considers the effect of MoO3 and SiO additives in telluride glasses on the shielding characteristics and protection of electronic microcircuits operating under conditions of increased radiation background or cosmic radiation. MoO3 and SiO dopants were chosen because their properties, including their insulating characteristics, make it...
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In this paper, the technology of synthesis of crystallites and nanocrystallites of nickel oxide on the surface of indium phosphide is described. This technology consists of two stages. In the first stage, porous indium phosphide is formed on the surface of a single crystal of indium phosphide. The formation of such a porous layer provides better ad...
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Low-temperature ultraviolet-excited photoluminescence (PL) and recombination luminescence (RL) properties of La-doped Ca2SnO4 have been investigated by luminescence, electron paramagnetic resonance (EPR) and optically-detected magnetic resonance (ODMR) techniques. Two PL and RL bands at 340 nm and 450 nm have been observed. PL excitation spectra me...
Article
Corundum (α-Al2O3) possesses a number of unique properties, including high tolerance to harsh radiation environment. Material functionality is strongly affected by radiation-induced structural defects, single interstitial-vacancy Frenkel pairs and their aggregates. Three novel paramagnetic two-electron defects with total spin S = 1 have been reveal...
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ZnSeO3 nanocrystals with an orthorhombic structure were synthesized by electrochemical and chemical deposition into SiO2/Si ion-track template formed by 200 MeV Xe ion irradiation with the fluence of 107 ions/cm2. The lattice parameters determined by the X-ray diffraction and calculated by the CRYSTAL computer program package are very close to each...
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Extended free‐volume positron trapping defects (positron trapping channel) and nanopores (positronium decaying channel) in the initial and modified MgAl2O4 ceramics sintered at 1200, 1300 and 1400 oC were investigated using positron annihilation lifetime spectroscopy within four‐component fitting procedure. It is established that the number and siz...
Article
A comprehensive theoretical study of the structure, electronic, optical, and elastic properties of ternary semiconductor silver thiogallate crystal AgGaS2 is carried out based on the density functional theory and dipole electron shifting model (DES) for finding a structure–properties relationship. The deformation and displacement parameters, descri...
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We present and discuss the results of surface relaxation and rumpling computations for ReO3, WO3, SrTiO3, BaTiO3 and BaZrO3 (001) surfaces employing a hybrid B3LYP or B3PW description of exchange and correlation. In particular, we perform the first B3LYP computations for O-terminated ReO3 and WO3 (001) surfaces. In most cases, according to our B3LY...
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Estimating and predicting space weather is important to the space industry and space missions. The driver of space weather, especially near the Earth, is solar activity, the study of which is an important task. In particular, there is a direction of problems based on models of solar magnetic field generation that require research. In our work, we b...
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Proper presentation and interpretation of the experimental spectroscopic data is critical to understanding of the luminescence of solids that can increase fundamental scientific knowledge and serve as a practical guide to the development of commercially useful phosphors and other functional optical materials. We find prevalence of erroneous interpr...
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An α-Al2O3 (corundum) possesses unique optical, electrical and mechanical properties, demonstrates high tolerance to heavy irradiation and, in particular, is in a short list of candidates for optical/diagnostics windows in advanced fission and forthcoming fusion (DEMO) reactors. However, material functionality is strongly affected by structural def...
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The BaGa2O4 ceramics doped with Eu3+ ions (1,3 and 4 mol%) were obtained by solid‐phase sintering. The evolution of defect‐related extended free volumes in the BaGa2O4 ceramics due to the increase of the content of Eu3+ ions has been studied using positron annihilation lifetime spectroscopy technique. It is established that the increase in the numb...
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Transformation of free‐volume extended defects in selectedchalcogenide glasses caused by thermal annealing for 10, 25 and 50 h were studied. For 80GeSe2‐20Ga2Se3 as well as for GeS2‐Ga2S3 glasses with different GeS2 and Ga2S3 contents (80GeS2–20Ga2S3, 82GeS2–18Ga2S3, 84GeS2–16Ga2S3) positron annihilation lifetime spectroscopy and Doppler broadening...
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The atomic structure of antiphase boundaries in Sr-doped lanthanum scandate (La1−xSrxScO3−δ) perovskite, promising as the proton conductor, was modelled by means of DFT method. Two structural types of interfaces formed by structural octahedral coupling were constructed: edge- and face-shared. The energetic stability of these two interfaces was inve...
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Due to its widespread application in modern industry, the ongoing development of all the most important technological directions in the field of sensors, oxygen membranes, and reforming is undoubtedly a promising trend in world research and development (R&D). The search for modern highly oxygen-conducting materials used as oxygen separation membran...
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In this work, we analyzed the optical absorption, X-ray diffraction analysis data, and mechanical properties along the ion path for Gd3Ga5O12 (GGG) single crystals irradiated with fast ⁸⁴Kr ions to fluences of 10¹³–10¹⁴ ion/cm². It was found that the optical absorption spectra of Czochralski-grown un-irradiated GGG crystal consist of relatively nar...
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Comparative ab initio calculations of SrTiO 3 , BaTiO 3 , PbTiO 3 , and SrZrO 3 (001) and (111) surfaces as well as oxygen vacancies The paper presents and discusses the results of our performed ab initio calculations for perovskites SrTiO 3 , BaTiO 3 , PbTiO 3 , and SrZrO 3 (001) and (111) surfaces by means of the hybrid B3PW or B3LYP description...
Article
Vacuum ultraviolet (VUV) excitation spectroscopy under synchrotron irradiation is a powerful tool for the investigation of luminescence properties of wide bandgap nanocrystalline phosphor materials. The advantages of selective excitation in a wide spectral range present the possibility to explore the different aspects of luminescence processes in n...
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Herein we demonstrate the specifics of using the positron annihilation lifetime spectroscopy (PALS) method for the study of free volume changes in functional ceramic materials. Choosing technological modification of nanostructured MgAl2O4 spinel as an example, we show that for ceramics with well-developed porosity positron annihilation is revealed...
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BaGa2O4 ceramics doped with Eu3+ ions (1, 3 and 4 mol.%) were obtained by solid-phase sintering. The phase composition and microstructural features of ceramics were investigated using X-ray diffraction and scanning electron microscopy in comparison with energy-dispersive methods. Here, it is shown that undoped and Eu3+-doped BaGa2O4 ceramics are ch...
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First-principles density functional theory (DFT) is employed to study the electronic structure of oxygen and gallium vacancies in monoclinic bulk β-Ga2O3 crystals. Hybrid exchange–correlation functional B3LYP within the density functional theory and supercell approach were successfully used to simulate isolated point defects in β-Ga2O3. Based on th...
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The study focuses on the optical properties of the CZTS multicomponent semiconductor absorber with 3 % “production” impurities of Cd, Na, O within the framework of the density functional theory using the generalized gradient approximation and the SCAPS program, as well as investigates their influence on the performance and efficiency of CZTS-solar...
Article
The natural spinel crystal MgAl2O4 containing the Cr³⁺ ions was studied experimentally and theoretically in this paper. The absorption and emission spectra at room and low temperatures were recorded. The experimental spectroscopic results were aided with the crystal field calculations, which returned the energy level schemes of the Cr³⁺ ions at the...
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Due to unique optical/mechanical properties and significant resistance to harsh radiation environments, corundum (α-Al2O3) is considered as a promising candidate material for windows and diagnostics in forthcoming fusion reactors. However, its properties are affected by radiation-induced (predominantly, by fast neutrons) structural defects. In this...
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The first principles hybrid DFT calculations were performed for small radius polarons - self-trapped electrons (STEL) and holes (STH) in Pb X 2 ( X = F, Cl, Br) crystals, widely used as...
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We computed the atomic shift sizes of the closest adjacent atoms adjoining the (001) surface F-center at ABO3 perovskites. They are significantly larger than the atomic shift sizes of the closest adjacent atoms adjoining the bulk F-center. In the ABO3 perovskite matrixes, the electron charge is significantly stronger confined in the interior of the...
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In this paper, the density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of the Ti3+ and Ti2+ ions substituted for the host Al atom in orthorhombic Pbnm bulk YAlO3 crystals. The disordered crystalline structure of YAlO3 was modelled in a large supercell...
Article
Corundum (α-Al2O3) is a technologically important material, in particular, widely used in optical applications such as luminescent radiation dosimeters, cryogenic scintillators and being considered as a promising candidate for windows in future fusion reactors. Its optical and mechanical properties are controlled by presence of radiation-induced (i...
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The influence of poly(titanium oxide) obtained using the sol-gel method in 2-hydroxyethyl methacrylate medium on the viscoelastic and thermophysical properties of interpenetrating polymer networks (IPNs) based on cross-linked polyurethane (PU) and poly(hydroxyethyl methacrylate) (PHEMA) was studied. It was found that both the initial (IPNs) and org...
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Due to the unique properties and wide array of applications of nanocrystalline materials based on titanium dioxide, the study of new synthesis approaches remains relevant. In this study, within the framework of the extraction-pyrolytic method (EPM), we suggest using the mixtures of Ti- and Eu-containing organic extracts based on valeric acid as pre...
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The unique properties and numerous applications of nanocrystalline titanium dioxide (TiO2) are stimulating research on improving the existing and developing new titanium dioxide synthesis methods. In this work, we demonstrate for the first time the possibilities of the extraction–pyrolytic method (EPM) for the production of nanocrystalline TiO2 pow...
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Gallium oxide β-Ga 2 O 3 is an important wide-band gap semiconductor. In this study, we have calculated the formation energy and transition levels of oxygen vacancies in β-Ga 2 O 3 crystal using the B3LYP hybrid exchange-correlation functional within the LCAO-DFT approach. The obtained electronic charge redistribution in perfect Ga 2 O 3 shows nota...
Article
The synthesis of CdTe nanocrystals (NCs) is performed by electrochemical deposition into prepared ion tracks in a a‐SiO2/Si‐n template. As a result, CdTe NCs are obtained in a wurtzite (WZ) crystal phase. The measurement of the current–voltage characteristics shows that the CdTe (WZ NC)/SiO2/Si system obtained in this way has n‐type conductivity. C...
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The precise study of the thermal annealing of the F2-type dimer defects, being under discussion in the literature for a long time and responsible for the number of absorption bands below 4.5 eV, has been performed in corundum single crystals irradiated by fast neutrons with a fluence of 6.9 × 10¹⁸ n/cm². The Gaussian components of the radiation-ind...
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The paper deals with the model research of electric transport characteristics of stressed and non-stressed FeSe monolayers. Transmission spectra, current-voltage characteristic (CVC) and differential conductivity spectra of two-dimensional FeSe nanostructure have been calculated within the framework of the density functional theory and non-equilibr...
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The electronic structure of Mn 2+ ion substituted for the host Y atom in orthorhombic bulk YAlO 3 crystals has been calculated by means of hybrid exchange-correlation functional HSE within density functional theory. The supercell approach has been used to simulate in Pbnm YAlO 3 crystal the point defects, Mn-dopant and compensated the F + center (o...
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The efficiency of stabilization of H centers as well as its dependence on the degree of uniaxial deformation are considered within the framework of the modified geometric model of alkali halides. It is shown that stabilization of H centers is difficult in KI and RbI crystals, while in other NaCl-type crystals it becomes quite probable. Under uniaxi...
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Original results on the EPR and photoluminescence Cr 3+ ions in natural magnesium aluminum spinel (MgAl 2 O 4) are presented. The photoluminescence spectra of Cr 3+ ions in natural MgAl 2 O 4 have been measured before and after irradiated by fast neutrons.
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Synchrotron radiation is applied to study visible and UV luminescence spectra and their excitation spectra of undoped as well as In and Sb doped cadmium iodide crystals at 10 K. The origin of principal luminescence bands and the role of impurities in the formation of emission centers are discussed. The luminescence properties have been explained ba...
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We report the results of ab initio calculations and analysis of systematic trends for the F centers in the bulk and on the (001) surface in oxide perovskites, such as BaTiO3 , SrTiO3 , SrZrO3 , and PbZrO3 , with a corresponding comparison of the F centers in perovskites with those in alkaline earth metal fluorides (CaF2 , BaF2 , and SrF 2). It was...
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The first-principles (ab initio) computations of the structural, electronic, and phonon properties have been performed for cubic and low-temperature tetragonal phases of BaTiO3 and SrTiO3 perovskite crystals, both stoichio-metric and non-stoichiometric (with neutral oxygen vacancies). Calculations were performed with the CRYSTAL17 computer code wit...
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Atomically smooth (001) surfaces of SrTiO 3 cut from the high-quality single crystals at two different miscut angles 0.9 and 7.0 deg between the real flat surfaces and crystallographic planes (001) were analyzed by means of the reflection high energy electron diffraction (RHEED) method from the room down to liquid helium temperatures. The diffracti...
Article
Original results on the EPR and photoluminescence Cr3+ ions in natural magnesium aluminum spinel (MgAl2O4) are presented. The photoluminescence spectra of Cr3+ ions in natural MgAl2O4 have been measured before and after irradiated by fast neutrons.
Article
Photoluminescence and cathodoluminescence of LiF crystals doped with different binary metal oxides were measured in the wide temperature range of 50-300 K and time interval of 10 −8 −10 −1 s after the nanosecond electron excitation pulse. Both as-grown those and crystals irradiated by an electron beam in range of absorbed dose up to 10 3 Gy were st...
Article
The first-principles (ab initio) computations of the structural, electronic, and phonon properties have been performed for cubic and low-temperature tetragonal phases of BaTiO 3 and SrTiO 3 perovskite crystals, both stoichiometric and non-stoichiometric (with neutral oxygen vacancies). Calculations were performed with the CRYSTAL17 computer code wi...
Article
Full-text available
Photoluminescence and cathodoluminescence of LiF crystals doped with different binary metal oxides were measured in the wide temperature range of 50−300 K and time interval of 10 −8 −10 −1 s after the nanosecond electron excitation pulse. Both as-grown those and crystals irradiated by an electron beam in range of absorbed dose up to 10 3 Gy were st...
Article
CdTe and CdO nanocrystals were synthesized by chemical deposition into a-SiO2/n-Si ion track template formed by 200 MeV Xe ion irradiation with the fluence of 10 8 ions/cm 2. Depending on the temperature of the solution CdTe + CdO and single-phase CdO with a hexagonal crystal structure were obtained, respectively. The study of the current-voltage c...
Article
In this paper, we have performed comparative analysis of EPR, optical absorption (OA) and luminescence spectra for a series of Gd3Ga5O12 (GGG) single crystals irradiated with fast neutrons with fluencies varied from 10¹⁶ to 10²⁰n/cm². In a crystal irradiated with the maximum neutron fluence, the EPR spectra demonstrated the formation of several par...
Article
The electronic structure and Raman scattering from face-centered cubic LiF with three types of vacancies — an F-center, an F′-center and a vacancy without electrons (vF) — has been calculated by means of hybrid exchange–correlation functional within density functional theory. Our modeling predicts the effective charge of 0.87e,1.50e and 0.10e on th...