The low-temperature luminescent properties of the 100 nm SiO2 films implanted with Zn and Zn + Mn ions were studied upon UV/VUV synchrotron excitation in spectral range of 4.5-10.7 eV. Implantation with Zn and Mn ions with different fluence leads to the formation of alpha-Zn2SiO4 nanoparticles and Si- quantum dots in ion irradiated films. Both X-Ray diffraction and photoluminescence spectroscopy data confirm the formation of willemite phase Zn2SiO4 in SiO2 matrix. The characteristic 2.4 eV emission band observed resembles the properties of classical Zn2SiO4:Mn phosphor, though no manganese were introduced into the films. Along with this, oxygen-deficient emission centers with singlet and triplet electron transitions are pronounced. PL excitation spectra demonstrate the contribution of willemite and silica band states, thus suggesting interphase energy transfer implementation. The exciton- and defect-coupled channels of PL excitation, which are affected by the concentration of implanted manganese, are revealed. Based on the spectroscopy data, schemes of mechanisms of PL excitation of willemite nanoparticles and silicon quantum dots and oxygen-deficient centers, are proposed.

CsLaSiS4 single crystals doped with Tb3+ and co-doped with Ce3+, Tb3+ ions were obtained by a high- temperature flux synthesis. XRD data demonstrate that the samples crystallize in the orthorhombic P nma space group without additional reflections belonging to the impurity phases. Low-temperature luminescent spectroscopy methods have been used to study the efficiency of radiative transitions and energy transfer between Ce3+ and Tb3+ ions. Additionally, the effect of irradiation with protons with an energy of 18 MeV from a cyclotron was studied. Spectral-kinetic measurements of pulsed cathodo- and photoluminescence of samples co-doped with Ce3* and Tb3* revealed bidirectional energy transfer processes between these ions, the parameters of nonradiative energy transfer Ce3+ -> Tb3+ were determined. The effect of concentration quenching is observed in undoped CsTbSiS4. The method of low-temperature thermally stimulated luminescence and the kinetics of pulsed cathodoluminescence indicate a high concentration of "shallow" carrier trapping centers in doped samples. When irradiating CsLaSiS4:0.5%Ce sample with protons, both the low-temperature emission of self-trapped excitons (STE) and the energy transfer STE -> Ce3+ decrease, the luminescence yield of defect-bound excitons (DBE) also decreases compared to the emission of Ce3+ ions, and defects are mainly formed, which are the centers of nonradiative recombination of band charge carriers.

In this report spectroscopic properties of KLuP2O7 phosphate doped with Pr3+ ions are presented. Among the presented results, there are spectra of photoluminescence (PL) at room temperature and T = 5 K, excited with selective UV photons, spectra of PL excitation, and electron spin resonance (ESR) measurements. Measurements of luminescence spectra were performed with non-irradiated samples and after irradiation with protons (E = 18 MeV). Measurements of ESR spectra were carried out after irradiation with fast electrons (E = 10 MeV). In the studied samples doped with Pr3+ ions, three typical channels of radiative relaxation of electron excitations were observed: interconfigurational d→f transitions, intraconfigurational f→f transitions and defect-related luminescence. After irradiation significant changes in emission characteristics were observed, including a redistribution of the intensity of interconfigurational transitions, an increase in defect-related luminescence and the manifestation of new emission centers. The generation of radiation-induced defects presumably occurs through the formation of complexes composed of phosphorus and oxygen atoms.

Ce+3 doped CsLaSiS4 single crystals were synthesized using high-temperature flux synthesis. XRD analysis showed that the products are isostructural to CsLaSiS4 and crystallize in orthorhombic space group Pnma. Absorption spectra were studied at room temperature, and photoluminescence properties were examined in the temperature range of 5-310 K. The energy of interband transitions E-g = 3.75 eV was determined at room temperature in the Tauc model. At room temperature, only a non-elementary d -> f emission band of Ce+3 ions was observed in the 520 nm region. The luminescence kinetics upon excitation by a pulsed cathode beam or X-ray synchrotron radiation exhibited a dominant nanosecond component. Decay time, as well as build-up time, decreased with increasing concentration of Ce+3 ions. Concentration quenching of Ce+3 emission was not observed up to 11.9 mol% of Ce+3 ions. At a low temperature of 5 K, new wide emission bands at 422 and 688 nm appeared in the photoluminescence spectrum. It is shown that the 422 nm band in the photoluminescence spectrum corresponds to host emission, specifically the luminescence of self-trapped excitons (STE). The 688 nm emission band corresponds to defect-related luminescence. STE emission is quenched according to the Mott law at temperatures above 26 K with an activation energy of 20 meV. An efficient energy transfer channel from the STE to the Ce+3 ion via the radiative resonance mechanism is observed. The emission of Ce+3 ions and defect-related luminescence can be excited by the intracenter way, due to electron-hole recombination, or by the creation of defect bound excitons. Based on the obtained spectroscopic data, a band scheme illustrating the processes of relaxation of electronic excitations at T = 5 K in Ce+3 doped CsLaSiS4 crystals is proposed.

A series of single crystals of CsLa1-& khcy;& Scy;& iecy;& khcy;SiS4 monophasic solid solution (x = 0-1) has been obtained for the first time by high-temperature flux synthesis. Methods of XRD and chemical analysis, absorption and low-temperature (from T = 5 K) luminescent spectroscopy were used. The results of the band scheme calculating using density functional theory correlate with spectroscopy data. One non-elementary d -> f emission band of Ce3+ ions is observed in the region of 520 nm in the luminescence spectra at room temperature at any value of the x parameter. The luminescence decay kinetics of Ce3+ ions upon excitation by a pulsed electron beam, X-ray synchrotron radiation or intracenter photoexcitation is characterized by a nanosecond component. As the parameter x increases, the decay time is reduced from 132 ns (x = 0.005) to 0.88 ns (x = 1). The luminescence decay kinetics upon photoexcitation at x = 0.005-0.12 is characterized by monoexponential decay with tau = 31.4 +/- 0.2 ns. Concentration quenching of the Ce3+ ion photoluminescence is not observed up to the value of the parameter x = 0.12; it only appears at x = 1. The anomalously short decay time of the Ce3+ ions luminescence in CsCeSiS4 upon both X-ray excitation and photoexcitation is associated with concentration quenching. At temperature 5 K, new intense bands at 408 and 688 nm in addition to the Ce3+ emission band observed in the photoluminescence spectra of nominally pure CsLaSiS4 or at the lowest parameter value x = 0.005. These bands correspond to the luminescence of self-trapped excitons (STE) and defects. With increasing x parameter, the STE emission band is reabsorbed by the absorption of Ce3+ ions and is quenched due to the resonance energy transfer STE -> Ce3+ center. Thermoluminescence glow curves of CsLa1-xCexSiS4 irradiated with X-ray at T = 90 K are characterized by several low temperature intense peaks, which indicates a high concentration of charge carrier traps.

A series of (Gd, Y, Yb, Tb, Ce)3Al2Ga3O12 compositionally disordered compounds with a garnet structure were prepared in the form of ceramics by sintering in oxygen at 1650 °C for 2 h and studied for the luminescent properties and interaction of ions entering the matrix host. The luminescence features of Ce3+ ions were found to be strongly dependent on the Yb concentration. Photoluminescence and scintillation kinetics are characterized by subnanosecond kinetics when the Yb index in the compound exceeds X = 0.3. It opens an opportunity to create an extremely fast and dense scintillation material emitting in a visible range. A further decrease in the Yb index in the compound leads to an increase in the intensity of Yb3+ infrared (IR) emission, whereas Ce3+ and Tb3+ ions contribute to the luminosity of the material by overlapping intra- and intereconfiguration luminescence bands in the spectral range of 300–700 nm. This finding opens an opportunity to create converter materials tolerant to the corpuscular radiation of isotope sources, providing a high efficiency of electric current production when coupled with a silicon photovoltaic element. The compounds were engineered at the nanoscale level, providing control over electronic excitation transfer between luminescent ions.

The manifestation of ytterbium ions in the microcrystals of the Sr2Y6.8YbSi6O26:Er0.2 solid solution with apatite structure was studied on the basis of low-temperature photoluminescence (PL) spectroscopy and spectral-kinetic measurement data. Intracenter down-conversion luminescence of Er3+ ions in the visible and IR ranges was detected. Up-conversion luminescence of Er3+ ions is observed upon IR excitation due to excitation of Yb3+ ions and subsequent energy transfer Yb3+ -> Er3+. Overlapping bands at 412 and 430 nm with a Stokes shift of less than 0.3 eV are observed in the PL spectra at room temperature. These emission bands are assigned to the spinallowed and spin-forbidden 4f135d -> 4f14 transitions from the low-spin and high-spin exciting states of Yb2+ ion, respectively. The PL decay kinetics for transitions from the low-spin states is characterized by a dominant component tau = 0.39 ns. An alternative model of Yb3+ luminescence center associated with a charge transfer band does not explain the data of low-temperature (5K) PL spectroscopy. At T = 5 K, a new wide emission band with a maximum at 696 nm and a Stokes shift of 1.1 eV appears in the PL spectrum. Two options of this PL band nature are considered. The first is the luminescence of defects having a vacancy nature. The second possible option is the manifestation of anomalous luminescence of Yb2+ ions, which occupy a different crystallographic position in the apatite crystal structure.

A method to create compositionally disordered compounds with a high number of cations in the matrices, that utilize the cubic spatial symmetry of the garnet-type crystalline systems is demonstrated. Mixtures of the garnet-type powdered materials solely doped with Ce were used to create atomic compositions of high complexity. Several mixed systems, namely Gd3Al2Ga3O12/(Gd,Y)3Al2Ga3O12, Y3Al5O12/Gd3Al2Ga3O12, and Y3Al5O12/Y3Al2Ga3O12 were annealed, compacted and sintered in air. The materials were evaluated for structural, luminescence, and scintillation properties. It was demonstrated that the properties of the resulting ceramics are a little dependent on the granularity of powders when the median particle size is below ~5 μm.

Compositionally disordered crystalline material (Gd,Y,Tb,Ce)3Al2Ga3O12 was demonstrated to be a highly effective converter of corpuscular ionizing radiation into light. The material was found to be radiation-tolerant to an intense 10 MeV electron beam and had a low temperature dependence on light yield. These findings open an opportunity to utilize the developed material to create long-living, high-flux sources of optical photons under the irradiation of isotope sources. Besides the purposes of the measurement of ionizing radiation by the scintillation method in a harsh irradiation environment, this puts forward the exploiting of the developed material for indirect isotope voltaic batteries and the consideration of a photon engine for travel beyond the solar system, where solar wind force becomes negligible.

GYAGG:Tb (Ce) scintillators have been confirmed to be promising sources of light emission when excited by an intense 150 keV electron beam. The saturation of the scintillation yield under such excitation conditions has been studied. To explain the results obtained, a model that considers the Auger quenching mechanism was used. The Ce-doped material did not show saturation, whereas a moderate 30% drop of the yield was measured in the Tb-doped sample at the highest excitation beam intensity ~1 A/cm2. This put forward a way to exploit the Tb-doped scintillator for indirect β-voltaic batteries.

Large-sized, high optical quality Gd2O3 single crystals were grown from a solution at T = 1145 degrees C using Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic (bixbyite) phase (c-phase). The absorption spectra and luminescence properties of Gd2O3 doped with Eu3+ and Tb3+ impurity ions were studied. The absorption spectrum of Gd2O3:Eu in the short wavelength region is mainly due to charge transfer transitions from O2-to Eu3+ (240-290 nm), which overlap with the Urbach tail of the host-absorption. Additionally, electronic transitions in Eu3+ (320-540 nm) and Gd3+ (245-315 nm) lanthanide ions contribute to the absorption spectrum. Intraconfigurational radiative f - f transitions in impurity ions are clearly observed upon both UV-and X-ray excitations. However, 6PJ & RARR; 8S7/2 radiative transitions in Gd3+ ions are completely unobservable. Based on the obtained spectroscopic data, the energy positions of the ground state of all di-and trivalent lanthanide ions, as well as the energies of intraconfigurational f - f and interconfigurational f - d electronic transitions in Gd2O3 crystals with a cubic structure, are calculated. The proposed electronic energy diagram is used to discuss efficient energy transfer between lanthanide ions.

In the current study, a number ofexperimental methods combinedwith ab initio simulations and charge transport simulationswere used to prove that oxygen vacancies are responsible for the chargetransport in thin lanthanum-doped Hf0.5Zr0.5O2 (HfZrO:La) films and to establish the main charge transportmechanism. Films synthesized by an atomic layer deposition methodwith a doping impurity concentration of 3.5 mol % are studied. Itwas shown that the electronic structure and optical properties ofoxygen vacancy in HfZrO:La are close to those of the oxygen vacancyin an undoped oxide. The method of oxygen vacancy generation by high-temperatureannealing of an oxide in an inert medium was used, and a model ofthe atomic structure of HfZrO:La with oxygen vacancies was created.By analyzing the different charge transport mechanisms in dielectrics,it was shown that the charge transport in HfZrO:La is uniquely describedby phonon-assisted electron tunneling between neutral neighboringtraps that have a thermal trap ionization energy W (t) = 1.3 eV. This value coincides with half of the bluephotoluminescence Stokes shift value, which is due to oxygen vacancies,and besides, it is very close to the oxygen vacancy ionization energiesfound for undoped HfO2, ZrO2, and Hf0.5Zr0.5O2. Thus, the traps responsible for thecharge transport in thin HfZrO:La films are oxygen vacancies.

This paper reports the spectroscopic properties of phosphates KLuP2O7, Sr9Sc(PO4)7, K3Lu(PO4)2, doped with Pr3+ ions. Photoluminescence (PL) spectra under selective excitation with UV photons, PL excitation spectra, and decay kinetics of pulsed cathodoluminescence are studied. Recordings of luminescence spectra were done with non-irradiated samples and after their irradiation with fast electrons (E = 10 MeV) or fast reactor neutrons. Three typical channels of electronic excitations radiative relaxation have been identified: interconfigurational d−f transitions, intraconfigurational f−f transitions in Pr3+ ions and luminescence associated with defects. After irradiation, significant changes in the luminescence characteristics were observed: a redistribution of the intensity of the intraconfigurational d−f transitions, an increase in the luminescence yield of defects and the manifestation of new emission centers. The formation of radiation-induced defects presumably occurs due to the formation of complexes consisting of phosphorus and oxygen atoms.

Optically active defects in modified silicon oxide films on a silicon substrate have been studied by low-temperature photoluminescence (PL) spectroscopy using excitation by synchrotron radiation in the vacuum ultraviolet region. Films of dry thermal silicon oxide obtained by treatment of stoichiometric SiO2 in hydrogen plasma, films of wet thermal silicon oxide, and films with low dielectric constant (so called "low-k" dielectrics) have been studied. Investigations of various type SiO2 films detect the PL centers, which can be conditionally divided into two groups. The first group includes intrinsic point defects, the different variants of oxygen-deficient centers (ODCs). The second group contains centers like the spatially confined excitons in silicon quantum dots (SiQDs). It is shown that SiQDs differ in spectral characteristics, are formed in different ways, due to the transformation and clustering of point defects such as E'-centers, ODC(I) and ODC(II). In this case, the size and spectral properties of quantum dots depend on the mechanism of their formation. Schemes for the conversion of these defects are proposed. It was found that for wet films and nonstoichiometric SiOx films treated in hydrogen plasma, "metastable" centers ODC(I) and ODC(II) arise only under the action of synchrotron radiation in the region of interband or exciton absorption and then they decay because of radiative relaxation. The absence of stable ODC centers in these films is due to their clustering and the formation of SiQDs. In "low-k" mesoporous films, on the contrary, silicon quantum dots SiQDs are not formed, but ODC(I) and ODC(II) centers are clearly manifested. A scheme of electronic transitions upon indirect excitation of silicon quantum dots through exciton states of the SiO2 matrix is considered. The presented results demonstrate the possibility of controlling the optical properties of silicon thin-film structures by creating in them both oxygen-deficient point defects and quantum dots of various sizes.

Understanding of host-to-impurity energy transfer process is crucial for the development of efficient and fast response scintillator materials. In this work, Pr3+ doped Na3LuSi3O9 (NLS) double salt silicate has been successfully synthesized using a high temperature solid-state reaction method and further comprehensively characterized by means of XRD measurements, crystal structure refinement, luminescence spectroscopic and time-domain study upon VUV-UV and X-ray synchrotron excitation, and thermally stimulated luminescence (TSL) study. Based on these results a model of host to Pr3+ 4f15d1 and 4f2 has been proposed. It has been demonstrated that NLS:Pr3+ has a good potential for fast response scintillator applications due to the presence of an efficient energy transfer from host electronic excitations to Pr3+ 4f15d1 states. The Pr3+ 4f15d1→4f2 emission reveals a good thermal stability and is characterized by a lifetime of about 16 ns. Upon pulse X-ray excitation the main fast decay component is accompanied by slower one with lifetime of about 64 ns that is ascribed to the presence of shallow traps which retrap carriers and cause appearance of delayed recombination. Parameters for the corresponding traps have been calculated based on the TSL glow curve analysis.

Large-size high optical quality Gd2O3 single crystals were grown from solution at T = 1145 degrees C by Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic phase (C-phase). Absorption spectra and luminescence properties of Gd2O3 doped with impurity Tb3+ ion were studied. The absorption spectrum is determined by electronic transitions in Gd3+ ion (spectral region of 245-315 nm) and interband electron transitions below 240 nm. Intraconfigurational radiative f-f transitions from 5D4 level in Tb3+ ion are clearly manifested upon both UV-and X-ray excitation. At the same time, 6PJ & RARR; 8S7/2 radiative transitions in Gd3+ ions are completely absent. This fact indicates high efficiency of nonradiative energy transfer from Gd3+ to Tb3+ ions. Thermo-luminescent spectroscopy shows the absence of charge carrier trapping centers, which proves the perfection of its crystal structure. The crystal under study shows high radiation resistance to high-energy (E = 10 MeV, D = 105 kGy) electron beam. However, the effects of irradiation appear only in the photoluminescence excitation spectra and thermally stimulated luminescence.

This paper reports the spectroscopic properties of praseodymium-doped phosphates, KLuP2O7, Sr9Sc(PO4)7, K3Lu(PO4)2 doped with Pr3+ ions. Spectra of photoluminescence (PL) upon selective UV photon excitation, PL excitation spectra as well as luminescence spectra and decay kinetics upon pulse synchrotron X-ray excitation were studied. Recordings of luminescence spectra were done with pure samples and after irradiating with fast electrons (E = 10 MeV) using linear electron accelerator. The absorbed dose varied in the range of 150–300 kGy. Pure samples demonstrated three typical channels of emission: interconfigurational d – f transitions, intraconfigurational f – f transitions and defect-related luminescence. After irradiating, two scenarios of changing optical properties were investigated: increasing of defect-related luminescence impact in total light output and “suppressing” of defect-located energy emission.

In this work luminescence properties of crystalline powders of Sr9Lu(PO4)7 doped with Pr3+ ions were studied upon excitation in UV range in temperature range 5-320 K. Photoluminescence spectra show intensive emission corresponding to radiative interconfigurational 5d→4f electronic transitions, weak narrow lines of intraconfigurational 4f→4f transitions as well as emission of two types of crystal lattice defects. Upon pulsed excitation, timing characteristics of emission related to the impurity center and defects were studied, as well as temperature dependence of emission yield. The processes of energy transfer between impurity center and defects are discussed.