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The possibility of development of an efficient phosphor converters (PC) for white LED (WLED) based on single crystalline films (SCF) of Ce3+ doped Tb3Al5O12 garnet (TbAG:Ce), grown using liquid-phase epitaxy method onto Y3Al5O12 (YAG) substrates, is evidenced for the first time in this work. The detail investigation of the structural properties of the TbAG:Ce SCF/YAG epitaxial structures was performed. High-resolution scanning transmission electron microscopy and composition analysis revealed an interface with high structural quality including the formation of a transition layer with a 5–7 nm thickness between TAG:Ce SCF and YAG substrate. The transition layer consisted of solid solutions between Tb3Al5O12:Ce and Y3Al5O12 garnets gradually changing from undoped YAG in substrate towards TbAG:Ce in the film and allowed to reduce the mismatch-stress. The absorption, cathodoluminescence, photoluminescence properties of TbAG:Ce SCFs were investigated as well. Furthermore, the dependence of photoconversion properties on the film thicknesses was studied to construct the prototype of efficient warm white LEDs. The change in the crystal thickness enabled tuning of the white light tons from cold white/daylight to neutral white. These results can be useful for the development of a novel generation of phosphor converters for white LEDs.

This article is directed on the creation of composite scintillators which are based on the films and crystals of R2Si2O7:Ce (R = Lu, Gd, La) pyrosilicates using the liquid phase epitaxy (LPE) growth method for application in the radiation monitoring of different components of mixed ionization fluxes. Such types of composite scintillators are epitaxial structures containing film scintillators grown by the LPE method onto the substrates of crystal scintillators. In this article, the film and crystal parts of the composite scintillators were fabricated from effective scintillation materials on the base of Ce3+ doped Gd2- x Lu x Si2O7 and Gd2- x La x Si2O7, and $x = {0}$ and 0.25 mixed pyrosilicates with various scintillation decay kinetics due to the different Lu/Gd/La cation content. We briefly report on the results of the LPE growth of the composite scintillators based on the Ce3+ doped (Lu,Gd)2Si2O7 films and (Gd,La)2Si2O7:Ce crystal substrates, as well as the results of investigation of their luminescent and scintillation properties.

This work is devoted to the development of two novel types of advanced composite scintillators based on single crystalline films (SCFs) of Lu3Al5O12 garnet (LuAG), doped with Ce3+ and Pr3+ ions, and substrates from single crystals (SCs) of Sc3+ doped LuAG using the liquid phase epitaxy (LPE) method. We show the possibility for simultaneous registration of α-particles and γ-quanta using separation of the decay kinetics of the SCF and crystal parts of such composite scintillators. Namely, large differences in the respective scintillation decay kinetics and decay time values tα and tγ are observed for LuAG:Ce SCF/LuAG:Sc SC and LuAG:Pr SCF/LuAG:Sc SC composite scintillators under excitation by α-particles from an 241Am (5.5 MeV) source and γ-quanta from a 137Cs (662 keV) source. Thus, both developed types of composite scintillators can be applied for simultaneous registration of α-particles and γ-quanta in mixed radiation fluxes. The rate of discrimination of the scintillation signals, coming from the SCF and SC parts of the LuAG:Ce SCF/LuAG:Sc SC composite scintillator, expressed by the tγ/tα ratio, is equal to 1.34–1.96 in the 0–1100 ns time interval. For the LuAG:Pr SCF/LuAG:Sc SC composite scintillators, more significant differences in the scintillation decay kinetics are achieved. In this case, the tγ/tα ratio for these composite scintillators reaches the values 9.6–15.6 in the wide 0–2500 ns time interval. This is the best result among all the types of composite scintillators we developed based on epitaxial structures of garnet compounds.

The work is dedicated to the investigation of Eu3+ multicenter formation and luminescent properties of Ca3Sc2Si3O12:Eu (CSSG:Eu) and Ca2YScMgSiO12:Eu (CYMSSG:Eu) single crystalline film (SCF) phosphors, grown by liquid phase epitaxy method onto Gd3Ga2.5Al2.5O12 (GAGG) and Y3Al5O12 (YAG) substrates, respectively. We have found notable differences in the luminescent properties of CSSG:Eu and CYMSSG:Eu SCFs caused by the Eu3+ multicenter formation in both garnets due to the different local surrounding of Eu3+ ions in the dodecahedral positions by the non-isovalent Sc3+/Mg2+ and Si4+ cations in the octahedral and tetrahedral positions of garnet hosts, respectively. A feature of the Eu3+ center creation in CYMSSG:Eu garnet in comparison with CSSG:Eu counterpart is the possibility of localization of Eu3+ ions in dodecahedral sites of both Ca2+ and Y3+ cations. However, based on the obtained results, we have presupposed preferable localization of the Eu3+ ions mainly in the Y3+ positions of this garnet.

This work is dedicated to the development of new types of composite thermoluminescent (TL) detectors for simultaneous registration of the different components of ionization radiation based on the single crystalline films (SCFs) of Ce3+-doped Lu3&minus, xGdxAl5O12:Ce (x = 0&ndash, 1.5) garnet and Y3Al5O12:Ce (YAG:Ce) substrates using the liquid phase epitaxy (LPE) growth method. For this purpose, the TL properties of the mentioned epitaxial structures were examined in Ris&oslash, TL/OSL-DA-20 reader under excitation by &alpha, and &beta, particles from 242Am and 90Sr-90Y sources. We have shown that the cation engineering of SCF content can result in more significant separation of the TL glow curves of SCFs and substrates under &alpha, particle excitations in comparison with the prototype of such composite detectors based on the Lu3Al5O12:Ce (LuAG:Ce)/YAG:Ce epitaxial structure. Specifically, the difference between the TL glow curves of Lu1.5Gd1.5Al5O12:Ce SCFs and YAG:Ce substrates increases up to 120 K in comparison with a respective value of 80 degrees in the prototype based on the LuAG:Ce/YAG:Ce epitaxial structure. Therefore, the LPE-grown epitaxial structures containing Lu1.5Gd1.5Al5O12:Ce SCFs and Ce3+-doped YAG:Ce substrate can be successfully applied for simultaneous registration of &alpha, particles in mixed fluxes of ionization radiation.

The work is dedicated to the growth and investigation of the luminescent and scintillation properties of single crystalline films (SCFs) of Ca2−xR1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu) mixed garnets with x = 0–0.25, grown using the liquid phase epitaxy method onto Y3Al5O12 substrates from PbO-B2O3 based flux. The absorption, luminescent and scintillation properties of Ca2−xY1+x Mg1+xSc1−xSi3O12:Ce and Ca2−xLu1+xMg1+xSc1−xSi3O12:Ce SCFs with x = 0 and 0.25 were investigated and compared with the reference YAG:Ce and LuAG:Ce SCFs. Using the Ca2+, Mg2+ and Si4+ alloying, the Ce3+ emission spectra in Ca2−xR1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu; x = 0–0.25) SCFs can be notably extended in the red range in comparison with YAG:Ce and LuAG:Ce SCFs due to the increase of crystal field strength and Ce3+ multicenter creation in the dodecahedral positions of the lattices of these mixed garnet compounds. Due to the formation of Ce4+ ions, the as-grown Ca2−x R1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu) SCFs at x = 0 and 0.25 show relatively low light yield. However, after annealing in reducing atmosphere (95% N2 + 5% H2) at T > 1000 °C, a recharging Ce4+→Ce3+ takes place. After that, these SCFs possess the light yield about of 30% and 31% in comparison with the reference YAG:Ce and LuAG:Ce SCFs, respectively, and a fast scintillation response with the decay times in the ns range under α–particles excitation by 239Pu (5.15 MeV) source.

The possibility of growth by the liquid phase epitaxy method of a new type of advanced composite scintillator based on Ce3+-doped single crystalline films (SCFs) of Lu1.5Gd1.5Al1.5Ga3.5O12 garnet and substrates from single crystals (SCs) of Gd3Al2.5Ga2.5O12:Ce garnet is evidenced for the first time in this work. We show the possibility of the simultaneous registration of α-particles and γ-quanta by way of separation of the scintillation pulse height spectra and decay kinetics of SCF and crystal parts of such a composite scintillator. Namely, the significant differences in the scintillation decay kinetics of Lu1.5Gd1.5Al1.5Ga3.5O12:Ce SCF/Gd3Al2.5Ga2.5O12:Ce SC composite scintillator under excitation by α-particles of a 241Am (5.5 MeV) source and γ-quanta of 137Cs (662 keV) source are observed. The respective tα/tγ decay times ratio in the 0–500 ns range reach up to 0.5 for this type of composite scintillator; e.g., the SCF scintillators is two times faster than the substrate scintillator. For this reason,...

This work presents our latest achievements in the development of advanced composite scintillators for simultaneous registration of α-particles and γ-quanta in mixed ionizing fluxes based on single crystalline films (SCFs) of Tb3Al3O12 : Ce (TbAG : Ce) garnet and Gd3Al2.5Ga2.5O12 : Ce (GAGG : Ce) single crystal (SC) substrates using the liquid phase epitaxy (LPE) growth method from a melt-solution based on a PbO–B2O3 flux. The separation of the signals from the SCF and SC components of such composite scintillators can be realized by means of registration of the difference in the scintillation decay times of SCF and substrate scintillators and can be achieved at a large K = t(SCF)/t(SC) ratio, which is usually above 2. The TbAG : Ce SCFs exhibit relatively fast scintillation response under α-particle excitation with decay times of t1/e = 344–380 ns and t1/100 = 3130–3770 ns. Meanwhile, the scintillation response of TbAG : Ce SCFs under α-particle excitation is significantly slower in the 500–4000 ns range than that of the GAGG : Ce crystals with decay times of t1/e = 270–280 ns and t1/20 = 1280–1300 ns. We have found that for TbAG : Ce/GAGG : Ce composite scintillators, the optimal K ratio changes from 2.0 to 3.0 at the registration of scintillations with shaping times of 700–4000 ns. For this reason, TbAG : Ce/GAGG : Ce composite scintillators possess the best scintillation properties among all known LPE grown analogues for simultaneous registration of α-particles and γ-quanta in mixed fluxes.

The study is dedicated to the development of scintillating screens for microimaging applications based on the single crystalline films (SCFs) of Eu3+-doped (Y,Lu,Gd,Tb)AlO3-mixed perovskites grown onto YAlO3 substrates using the liquid phase epitaxy (LPE) method with the objective to optimize their X-ray stopping power and light yield. We confirm that the Eu3+-doped YAlO3 and TbAlO3 SCFs and full set of Lu1−xGdxAlO3 SCFs with x values in the x = 0–1.0 range can be crystallized on YAlO3 substrates using the LPE technique. The structural quality of films was studied using X-ray diffraction. The optical properties of Lu1−xGdxAlO3:Eu (x = 0–1) SCFs and TbAlO3:Eu mixed perovskites were also studied in this work in comparison with YAlO3:Eu SCF counterpart using the absorption, cathodoluminescence, photoluminescence (PL) emission and excitation spectra and PL decay kinetics as well as light yield measurements under e-beam and α-particles excitation. The Gd3+ → Eu3+ and Tb3+ → Eu3+ energy transfer processes are observed in Lu1−xGdxAlO3 and TbAlO3:Eu SCFs, respectively, increasing the efficiency of the Eu3+ luminescence in the perovskite hosts. Meanwhile, the highest light yield of the cathodoluminescence (CL) and radioluminescence (RL) under excitation by α-particles is found only in YAlO3:Eu, Lu0.5Gd0.5AlO3:Eu and GdAlO3:Eu SCFs. The light yield of CL and RL of these SCFs is notably higher than that in TbAlO3:Eu and LuAlO3:Eu SCFs and they even slightly (9–11%) overcome the light yield of the conventional Gd3Ga5O12:Eu SCF screens that are used in the microimaging detectors.

The work devoted to the investigation of a new luminescent and scintillation material based on the single crystalline films (SCFs) of Tm 3−x Lu x AG:Ce garnet; x = 0–1.5, grown by LPE method from PbO based flux. The best scintillation properties are achieved for SCFs of Tm 1.5 Lu 1.5 Al 5 O 12 :Ce composition. We have found that direct Tm → Ce and backside Ce → Tm energy transfer processes are observed in Tm 1.5 Lu 1.5 Al 5 O 12 :Ce. Due to elimination of traps in the 300–450 °C range, the relatively fast scintillation decay is realized in highly doped Tm 1.5 Lu 1.5 Al 5 O 12 :Ce SCFs. For this reason, Tm doping can be considered as a suitable way for improvement of the scintillation efficiency in other Ce 3+ doped garnet compounds.

In this work, we present for the first time the results on crystallization and investigation of the luminescence properties of new prospective phosphors based on single crystalline films (SCFs) of Ce3+-doped Ca2YMgScSi3O12 silicate garnet, grown by the liquid phase epitaxy (LPE) method onto Y3Al5O12 (YAG) substrates. The luminescence properties of Ca2YMgScSi3O12:Ce SCFs were compared with the properties of the reference YAG:Ce SCF sample. The influence of thermal annealing at 1000–1300 °C in a N2/H2 reducing atmosphere on the optical properties of Ca2YMgScSi3O12 SCFs was investigated as well. The results of this research can be suitable for the development of a new generation of white LED converters and scintillators based on the epitaxial structures of Ca2+–Si4+ containing garnets, grown by the LPE method onto undoped or doped substrates of garnet compounds.

UV emitting scintillating screens based on single crystalline films (SCFs) of Lu3Al5−xGaxO12:Pr garnet have been developed by the liquid phase epitaxy (LPE) growth method onto Y3Al5O12 (YAG) substrates using a lead-free BaO based flux. The absorbance, luminescence and scintillation properties of these SCFs have been investigated depending on the Ga content in the x = 0–1.9 range. We have found that the absorption and luminescence spectra of Pr3+ ions as well as the scintillation light yield (LY) and decay kinetics of Lu3Al5−xGaxO12 SCFs are non-linearly affected by the gallium concentration x in the mentioned solid solution due to preference for the distribution of Ga3+ and Al3+ ions between the tetrahedral and octahedral positions of the garnet host, respectively. The best scintillation properties of Lu3Al5−xGaxO12:Pr SCFs are achieved at the Ga content in the x = 1.0–1.2 range. The LY of the Lu3Ga1.2Al3.8O12:Pr SCF is comparable with the LY of the best reference LuAG:Pr single crystal counterpart and significantly (up to 3 times) overcomes the LY of LuAG:Pr and Lu3Al4–3.5Ga1.0–1.5O12 SCFs, grown onto the YAG substrates from the conventional PbO–B2O3 flux.

The paper is dedicated to development of UV emitting scintillating screens for microimaging applications based on the single crystalline films (SCFs) of Ce doped Gd 1− x Lu x AlO 3 and Pr 1 − x Lu x AlO 3 ( x =0–1) multicomponent perovskites grown onto YAlO 3 (YAP) substrates using the liquid phase epitaxy (LPE) method with the objective to improve the X-ray stopping power. Recently Riva et al. [1] have reported that the full set of Gd x Lu 1 − x AlO 3 SCFs with x values in x =0−1.0 range can be crystallized on YAP substrates using this technique. We report here that Pr x Lu 1− x AlO 3 SCFs with x values in x =0–0.5 range can be grown also by the LPE method from PbO-B 2 O 3 flux onto the same YAP substrates. The structural quality of the films was studied using X-ray diffraction. The optical properties of Ce 3+ doped of Gd 1− x Lu x AlO 3 and Pr 1− x Lu x AlO 3 ( x =0−1) multicomponent perovskite films, studied by traditional spectroscopic methods, such as absorption, cathodoluminescence, photoluminescence and light yield measurements under α–particles excitation, are also reported in this work. We have shown that Pb 2+ flux related impurity has significantly larger influence on the light yield of Pr 0.5 Lu 0.5 AlO 3 :Ce, GdAlO 3 :Ce and Gd 0.5 Lu 0.5 AlO 3 :Ce SCFs in comparison with the YAP:Ce and LuAlO 3 :Ce counterparts grown onto YAP substrates.

The work is dedicated to the investigation of the luminescent and scintillation properties of the LiLuP4O12:Ce tetraphosphate, as a new scintillation material. The LiLuP4O12:Ce polycrystalline samples were grown by the Micropulling down (MPD) method. Under e-beam excitation and excitation with energy above the band gap of host, the LiLuP4O12:Ce crystals possess very strong Ce3+ luminescence in the UV range in the bands peaked at 334 and 355 nm with a lifetime of 23 ns at room temperature. We have found that the scintillation light yield (LY) of polished plates prepared from MPD grown LiLuP4O12:Ce samples is relatively high and comparable with the LY of reference BGO crystal. Future improvement of the scintillation LY is expected at the optimization of the growth conditions of this compound. The energy structure of Ce3+ ions, related to the 4f-5d transitions of Ce3+ ions in the 3.7-25 eV range, was determined from the excitation and emission spectra of LiLuP4O12:Ce crystal under excitation by synchrotron radiation. We have also determined the energy of creation of excitons bound with Ce3+ ions and estimated the energy gap in LiLuP4O12 host, which is equal to 8.5 and > 9.0 eV, respectively.

The luminescence, scintillation, and photoconversion properties of the single crystals of Ce3+ doped Tb3−xGdxAl5-yGayO12 (х = 0–1.5; у = 2–2.5) mixed garnets, grown by the micro-pulling-down (μ-PD) method, are investigated as a function of the Tb/Gd ratio with the aim of development of phosphor-convertors of white LED and scintillators. The partial Tb3+ substitution by Gd3+ cations leads to the suitable change of the crystal field splitting of the 5d energy levels of Ce3 ions due to different sizes of the Gd3+ and Tb3+ cations. For this reason, the cation engineering enables to improve the luminescence and scintillation characteristics of Tb3−xGdxAl3-2.5Ga2-2.5O12 crystals due to increasing the efficiency of Gd3+→ Tb3+→ Ce3+ cascade energy transfer observed in these solid solutions. We have shown that from all the crystals under study, the Tb3-xGdxAl2.5Ga2.5O12:Ce (х = 1–1.5) crystal is the best promising candidate for the photoconversion and scintillation applications.

This work deals with the growth of Ce3+ doped Gd3−xLuxAl5−yGayO12 mixed single crystals garnets by the micro-pulling down method and their development as phosphor-convertors of white LED (pc-WLED) and scintillators. In this research, the influence of combined technique of the “band-gap engineering” and “positioning of Ce3+ 5d-levels” in Gd3−xLux Al5−yGayO12 single crystals at x = 0 – 1.5 and y = 2–2.5 ranges, is studied with the aim to improve the material properties such as color-rendering properties of pc-WLEDs, as well as scintillation. The luminescent, scintillation and photoconversion properties of Gd3−xLuxAl5−yGayO12:Ce crystals were investigated as a function of the Gd/Lu ratio. We reviled that Gd3−xLuxAl3−2.5Ga2−2.5O12:Ce crystals at × = 1–1.5 show the best photoconversion and scintillation properties.

The paper is dedicated to the investigation of the luminescence of Sc 3+ and La 3+ isoelectronic impurities in Y 2 SiO 5 (YSO) single crystalline films (SCF), grown by the liquid phase epitaxy (LPE) method, and in the powder analogs of these compounds prepared using the ceramic technology. The Sc 3+ and La 3+ dopants replacing the Y 3+ cations in Y1and Y2 positions of YSO host introduce the strong complex emission bands in the UV range peaked at 330 and 345 nm, respectively. The Sc 3+ and La 3+ dopant in YSO matrix yields also the strong TSL peaks at 400 and 405 K related to the ScY and ScLa centers formation, respectively. The luminescence and scintillation properties of YSO SCFs doped with Sc 3+ and La 3+ ions and co-doped with Ce 3+ ions on the trace impurity level have been also studied in our work. We have found that the light yield (LY) of these YSO:Sc and YSO:La SCFs can reach 50–65% of LY in reference YSO:Ce SCF due to strong quenching influence of Pb 2+ ions. Finally, the potential of Sc 3+ and La 3+ doped SCF of orthosilicates for creation of heavy scintillation screens, emitting in the UV range, is discussed.

The paper is dedicated to study the luminescent and scintillation properties of the Al 2 O 3 :Ce single crystalline films (SCF) grown by LPE method onto saphire substrates from PbO based flux. The structural quality of SCF samples was investigated by XRD method. For characterization of luminescent properties of Al 2 O 3 :Ce SCFs the cathodoluminescence spectra, scintillation light yield (LY) and decay kinetics under excitation by α-particles of Pu 239 source were used. We have found that the scintillation LY of Al 2 O 3 :Ce SCF samples is relatively large and can reach up to 50% of the value realized in the reference YAG:Ce SCF. Using the synchrotron radiation excitation in the 3.7–25 eV range at 10 K we have also determined the basic parameters of the Ce 3+ luminescence in Al 2 O 3 host.

The paper is devoted to investigation of the luminescent properties of Dy3+ and Dy3+-Ce3+ doped single crystalline films (SCF) grown by LPE method from PbO–B2O3 flux. We have found that the YAG:Dy and YAG:Dy,Ce SCFs possess bright cathodoluminescence in the visible range and good scintillation figure of merit. For this reason LPE grown YAG:Dy and YAG:Dy,Ce SCF are proposed for different applications, namely, as cathodoluminescence screens or screens for microimaging. The Dy3+ co-doping can be also proposed for improvement of the scintillation efficiency of the Ce3+ doped garnet compounds in the SCF form due to Dy3+→ Ce3+ energy transfer and removing the trap related centers in the above RT range.

In this work, investigation of the spectroscopic parameters of the luminescence of Yb 3+ ions in single crystalline films of Lu 3 Al 5 O 12 and Y 3 Al 5 O 12 garnets was performed using the synchrotron radiation excitation with the energy in the range of Yb 3+ charge transitions (CT), exciton range and the onset of interband transitions of these garnets. The basic spectroscopic parameters of the Yb 3+ CT luminescence in LuAG and YAG hosts were determined and summarized with taking into account the differences in the band gap structure of these garnets.

The Pr3+ d–f luminescence was investigated in the single crystalline films (SCF) of Lu3Al5−xGaxO12:Pr garnet solid solution at x = 1–3, grown by the liquid phase epitaxy (LPE) method from the melt-solution based on the PbO–B2O3 flux. The shape of CL spectra and decay kinetics of Pr3+ ions in Lu3Al5−xGaxO12 SCFs strongly depend on the total gallium concentration x and distribution of Ga3+ ions between the tetrahedral and octahedral position of the garnet host. The best scintillation properties of Lu3Al5−xGaxO12:Pr SCF are achieved at the nominal Ga content in melt-solution in the x = 2–2.5 range.

The paper is dedicated to development of the novel scintillating screens based on single crystalline films (SCF) of Ce doped ${{\rm Lu}_{3 - {\rm x}}}{{\rm Tb}_{\rm x}}{{\rm Al}_{5 - {\rm y}}}{{\rm Ga}_{\rm y}}{{\rm O}_{12}}$ multicomponent garnets at ${\rm x} = 2 - 3$ and ${\rm y} = 0 - 2.5$ onto ${{\rm Y}_3}{{\rm Al}_5}{{\rm O}_{12}}$ (YAG) and ${{\rm Gd}_3}{{\rm Al}_{2.5}}{{\rm Ga}_{2.5}}{{\rm O}_{12}}$ (GAGG) substrates using the liquid phase epitaxy (LPE) method. We report the optimized content and high scintillation figure of merit of SCF of these garnets grown by the LPE method with using PbO based flux. Namely, the ${{\rm Tb}_3}{{\rm Al}_{2.5}}{{\rm Ga}_{2.5}}{{\rm O}_{12}}:{\rm Ce}$ SCFs possess the highest values of light yield (LY) compared to all earlier investigated SCF samples, with their LY exceeding by 2.35 and 1.15 times the LY values for YAG:Ce and LuAG:Ce SCF scintillators, respectively. The SCFs of the mentioned compounds show very lower thermoluminescence in the above room temperature range and relatively fast scintillation decay.

The work is related to the investigation of scintillation and luminescent properties of single crystalline films (SCF) of solid solutions of Ce 3+ doped Y 3− x Lu x Al 5 O 12 :Ce garnets with x value in the 0–3 range. We have shown a possibility of realization of high-energy shift of the Ce 3+ ion emission spectrum in these garnets up to 22 nm. We have also found that the light yield of the radioluminescence under α-particle excitation of LuAG:Ce SCF can exceed by 1.3 times the corresponding values for the YAG:Ce SCF counterpart. For investigation of the luminescent properties of Y 3− x Lu x Al 5 O 12 :Ce SCF at different x values the luminescent spectroscopy of these SCFs under excitation by synchrotron radiation in the VUV range was performed.

The paper deals with investigation of the luminescent properties of Er and Er/Ce doped solid solutions of Y 1− x Yb x AG garnets with x values ranging from 0 to 3.0, prepared by the LPE method in the form of single crystalline films (SCF). We have found that the effective Ce 3+ →Yb 3+ energy transfer is observed in the Y 3− x Yb x Al 5 O 12 :Er,Ce garnets (Y 3− x YbAG:Er,Ce). Apart from that, strong enhancement of the Er 3+ upconvesion luminescence in Y 3− x Yb x AG:Er,Ce garnets was found due to the Ce 3+ codoping. Among all the investigated samples of solid solutions of mixed Y 3− x Yb x AG:Er,Ce garnets, the highest intensity of the up-conversion luminescence is observed for the Y 1.5 Yb 1.5 AG:Er,Ce SCF.

The dependences of microhardness H, electrical conductivity σ, charge carrier mobility μH, the Seebeck coefficient S, and thermoelectric power factor P = S2σ on the composition of Bi1-xSbx solid solutions in the vicinity of pure Sb (x = 1.0–0.975) were obtained. In the range of x = 0.9925–0.9875, an anomalous decrease in H and S and increase in σ and μH with increasing Bi concentration were observed. For all the alloys, the dependences of H on the load on an indenter G were plotted. It was found that the H(G) dependences for samples with x smaller than ~ 0.99 and for samples with x exceeding 0.99, exhibit different behavior. The results obtained are interpreted on the basis of our assumption about the existence of a percolation-type phase transition from impurity discontinuum to impurity continuum that occurs in any solid solution.

The Bi₂Se₃ thin films with thicknesses d = 7-420 nm were grown by thermal evaporation in vacuum of stoichiometric n-Bi₂Se₃ crystals onto heated glass substrates under optimal technological conditions determined by the authors. The growth mechanism, microstructure, and crystal structure of the prepared thin films were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. It was established that the prepared thin films were polycrystalline, with composition close to the stoichiometric one, did not contain any phases apart from Bi₂Se₃, were of a high structural quality, and the preferential growth direction [001] corresponded to the direction of a trigonal axis C₃ in a hexagonal lattice. The films, like the initial crystal, exhibited n-type conductivity. It was shown that with increasing film thickness, the grain size and the film roughness remain practically the same at thicknesses d < 100 nm, and after that increase, reaching their saturation values at d ~ 300 nm. It follows from the results obtained in this work that using the method of thermal evaporation in vacuum from a single source, one can prepare thin n-Bi₂Se₃ films of a sufficiently high structural quality with a composition close to the stoichiometric one and the preferential growth orientation. Тонкі плівки з товщинами d = 7-420 нм вирощені методом термічного випаровування у вакуумі кристалів стехіометричного n-Bi₂Se₃ на нагріті скляні підкладки при оптимальних технологічних умовах. Досліджено механізм росту, мікроструктуру та кристалічну структуру виготовлених плівок з використанням методів рентгенівської дифрактометрії, скануючої електронної мікроскопії, енергодисперсійної рентгенівської спектроскопії, фотоелектронної рентгенівської спектроскопії та атомної силової мікроскопії. Встановлено, що виготовлені тонкі плівки є полікристалічними, мають склад, близький до стехіометричного, не одержують інших фаз, окрім Bi₂Se₃, високої структурної якості, переважний напрямок росту – напрямок [001] відповідає напрямку тригонаьної осі C₃ у гексагональній решітці. Плівки, як і вихідний кристал, мають n-тип провідності. Показано, що зі збільшенням товщини плівки розмір зерна і шорсткість залишаються постійними при товщині d < 100 нм, потім зростають, досягаючи насичення при d ~ 300 нм. З отриманих результатів випливає, що, використовуючи метод термічного випаровування у вакуумі з одного джерела, можна приготувати тонкі n-Bi₂Se₃ плівки досить високої структурної якості зі складом, близьким до стехіометричного, і з переважним напрямком росту.

The dependences of the electrical conductivity, Seebeck coefficient and Hall coefficient on the thickness (d = 20–155 nm) of the n-type thin films grown on the glass substrates by the thermal evaporation in vacuum of the n-type Bi2Te3 topological insulator crystals have been measured. It has been established that these dependences have an oscillatory character with a substantial amplitude. The obtained results are interpreted in terms of quantum size effects, taking into account the peculiar properties of the surface layers of the Bi2Te3 films connected with the topological insulator nature of the bismuth telluride.

Low temperature, infrared transmission spectra of lutetium aluminum garnet (LuAG) bulk crystals and epitaxial layers doped with Ce are presented. In the region of intra-configurational 4f–4f transitions the spectra of the bulk LuAG crystal exhibit the signatures of several different Ce3+ related centers. Apart from the dominant center, associated with Ce substituting lutetium, at least six other centers are found, some of them attributed to so-called antisite locations of rare-earth ions in the garnet host, i.e., ions in the Al positions. X-ray diffraction data prove lattice expansion of bulk LuAG crystals due presence of rare-earth antisites.

The paper is dedicated to development of the scintillators based on single crystalline films of Ce doped (GdLaYLu) 3 (AlGaSc) 5 O 12 multi-component garnets onto Gd 3 Ga 5 O 12 substrates using the liquid phase epitaxy method.

V2VI3 compounds and solid solutions based on them are known to be the best low-temperature thermoelectric (TE) materials. The predicted possibility of enhancement of the TE figure of merit in two-dimensional (2D) structures has stimulated studies of the properties of these materials in the thin-film state. The goal of the present work is to study the dependences of the Seebeck coefficient S, electrical conductivity σ, Hall coefficient RH, charge carrier mobility μH, and TE power factor P = S2σ of Bi2Te3 thin films on the composition of the initial bulk material used for preparing them. Thin films with thickness d = 200 nm to 250 nm were grown by thermal evaporation in vacuum of stoichiometric Bi2Te3 crystals (60.0 at.% Te) and of crystals with 62.8 at.% Te onto glass substrates at temperatures TS of 320 K to 500 K. It was established that the conductivity type of the initial material is reproduced in films fairly well. For both materials, an increase in TS leads to an increase in the thin-film structural perfection, better correspondence between the film composition and that of the initial material, and increase in S, RH, μH, σ, and P. The room-temperature maximum values of P for the films grown from crystals with 60.0 at.% and 62.8 at.% Te are P = 7.5 × 10−4 W/K2 m and 35 × 10−4 W/K2 m, respectively. Thus, by using Bi2Te3 crystals with different stoichiometry as initial materials, one can control the conductivity type and TE parameters of the films, applying a simple and low-cost method of thermal evaporation from a single source.

The work deals with the growth and investigation of luminescent properties of scintillators based on the single crystalline films (SCF) of the Ce3+ doped Lu3−xGdxAl5−yGayO12 multicomponent garnets prepared by the Liquid Phase Epitaxy (LPE) method. We show that full set of Lu3−xGdxAl5−yGayO12 SCFs with x values in the 1.25–1.5 range and y values ranging from 0 to 4.0 in melt solution (MS) can be successfully crystallized by the LPE method onto Y3Al5O12 substrates from the MS based on PbO–B2O3 flux. The absorption, X-ray excited luminescence, photo-luminescence, thermoluminescence and also the light yield measurements under excitation by α-particles of Pu239 and Am241 radioisotopes were further employed for the characterization of the Lu3−x GdxAl5−yGayO12 SCF. We show that among all the investigated Lu3−xGdxAl5−yGayO12:Ce SCF scintillators, the best LY is realized in the Lu1.5Gd1.5Al1.5Ga3.5O12:Ce sample composition in MS.

The growth mechanism, microstructure, and crystal structure of the polycrystalline nBi2Te3 thin films with thicknesses d = 15 – 350 nm, prepared by thermal evaporation in vacuum onto glass substrates, were studied. Bismuth telluride with Te excess was used as the initial material for the thin film preparation. The thin film characterization was performed using X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scan electron microscopy, and electron force microscopy. It was established that the chemical composition of the prepared films corresponded rather well to the starting material composition and the films did not contain any phases apart from Bi2Te3. It was shown that the grain size and the film roughness increased with increasing film thickness. The preferential growth direction changed from [00l] to [015] under increasing d. The X-ray photoelectron spectroscopy studies showed that the thickness of the oxidized surface layer did not exceed 1.5 – 2.0 nm and practically did not change in the process of aging at room temperature, which is in agreement with the results reported earlier for single crystals. The obtained data show that using simple and inexpensive method of thermal evaporation in vacuum and appropriate technological parameters, one can grow n-Bi2Te3 thin films of a sufficiently high quality. Телурид вісмуту (Bi 2 Te 3 ) є ефективним термоелектричним матеріалом, і виготовлення тонких плівок Bi 2 Te 3 з хорошими термоелектричними властивостями є необхідною умовою для реалізації потенціалу цих матеріалів у застосуванні мікропристроїв. Контрольоване осадження вмісту та термічна обробка з низьким негативним впливом є двома основними проблемами при виготовленні високоефективних тонких плівок. У цьому дослідженні стехіометричний Bi 2 Te 3тонкі плівки були успішно виготовлені за допомогою двоетапного процесу термічної пари з одним джерелом випаровування. Потім швидкий термічний процес, який міг уникнути втрати компонентів, був використаний для подальшого покращення кристалічності та термоелектричних властивостей тонких плівок. Коефіцієнт Зеєбека тонких плівок Bi 2 Te 3 явно збільшився після швидкої термічної обробки, що призвело до підвищення коефіцієнта потужності та хорошої гнучкості. Такі тонкі плівки демонстрували низьку теплопровідність через їх нанорозмірні зерна, що призвело до високого ZT гнучких тонких плівок Bi 2 Te 3

The YAP:Mn single crystalline films (SCF) have been crystallized by liquid phase epitaxy (LPE) method onto YAP substrates. The cathode- (CL) and photo-luminescence (PL) spectra of the YAP:Mn SCF were analyzed for determination of the preferable valence states of manganese ions which are realized in these SCF depending on Mn content in the 0.01–0.81 at.% range. The thermoluminescence (TL) properties of YAP:Mn SCF with the different Mn content above the RT range were also examined in comparison with the properties of YAP:Mn single crystal counterpart. We show that YAP:Mn (0.01 at.%) SCF possesses effective TL properties both under α-particle and γ-quanta excitation with main TSL peaks at 130 and 195 °C. We assume that the different valence states of Mn ions are responsible for their TL properties, e.g. both emission and trapping centers in YAP:Mn are formed mainly by the different valence states of Mn ions.

Single crystalline films (SCFs) of undoped and Ce3+ doped Y2SiO5 (YSO) and Lu2SiO5 (LSO) orthosilicates were crystallized for the first time by liquid phase epitaxy method onto undoped YSO substrates from melt-solution based on PbO–B2O3 flux. The scintillation and luminescent properties of YSO:Ce and LSO:Ce SCFs were compared with the properties of bulk single crystal counterparts. We show that the peculiarities of luminescent properties of YSO:Ce and LSO:Ce SCFs in comparison with the crystal analogues are caused by the different distribution of Ce3+ ions over Y1/Lu1 and Y2/Lu2 positions of YSO and LSO host and strong influence of Pb2+ flux-related impurity on luminescent properties of Ce3+ ions.

Single crystalline films (SCF) of Lu 2 SiO 5 :Ce (LSO:Ce), (Lu 1− x Gd x ) 2 SiO 5 :Ce (LGSO:Ce) and LGSO:Ce,Tb orthosilicates with thickness of 2.5–21 μm were crystallized by liquid phase epitaxy method onto undoped LSO substrates from melt-solution based on PbO–B 2 O 3 flux. The concentration of Gd was varied in the range of x =0.2–0.7 formula units (f.u.). In the case of LGSO:Ce SCF growth we do not use any additional doping for reducing the misfit between the SCF and substrate lattices. The luminescence and scintillation properties of LSO:Ce, LGSO:Ce and LGSO:Ce,Tb SCFs were mutually compared and confronted with the performance of reference LSO:Ce and LYSO:Ce crystals. With increasing Gd content the luminescence spectrum of LGSO:Ce SCF is gradually red-shifted with respect to that of LSO:Ce SCF. The LY of (Lu 1− x Gd x )SO:Ce SCF becomes lower in comparison with that for LSO:Ce SC at increasing Gd content in the range of x =0.2–0.7 f.u. The peculiarities of luminescence properties of LSO:Ce and LGSO:Ce SCFs in comparison with crystal analogs are explained by the different distribution of Ce 3+ over Lu1 and Lu2 positions of LSO host and by the influence of Pb 2+ contamination coming from the flux used for the film growth.

Single crystalline films (SCF) of Lu2SiO5 (LSO) and Lu2SiO5:Ce (LSO:Ce) silicates with thickness of 2.5–15 μm were crystallized by liquid phase epitaxy method onto undoped LSO substrates from melt-solution based on PbO–B2O3 flux. The scintillation and luminescence properties of LSO:Ce SCF were compared with the properties of LSO:Ce single crystal. The peculiarities of luminescence properties of LSO:Ce SCF in comparison with crystal analog can be due to different distribution of Ce3+ over the Lu1 and Lu2 positions of LSO host and are further influenced by Pb2+ flux-originated contamination.

CsI:Tl films have been crystallized by the liquid phase epitaxy (LPE) method from CsI:Tl (0.3 mol.%) crystalline salt onto CsI substrates. The luminescent and scintillation properties of CsI:Tl films are systematically compared with the corresponding properties of CsI:Tl (0.3 and 0.03%) crystals grown from the melt. The luminescence of CsI:Tl films and CsI:Tl (0.03%) crystals in the bands peaked at 2.52 and 2.22 eV is related to the radiative relaxation from the weak-off and strong-off configurations of excitons localized around Tl+ ions, respectively. Apart from single Tl+ centers, in highly doped CsI:Tl (0.3%) crystals creation of Tl+ dimer centers occurs. These centers form the additional emission bands peaked at 2.42 and 1.98 eV related to the weak-off and strong-off configurations of excitons localized around Tl+ dimer centers. We found that the dominant mechanism of excitation of the strong-off luminescence of localized excitons in CsI:Tl films and crystals is the charge-transfer transition between I– anions and Tl+ ions in single and dimer centers.

The efficiency of the final stage of luminescent center excitation mechanism in scintillator plays a major role to accomplish fast and bright scintillation materials. We focus our attention on complex oxide crystals doped with Ce3+ because the Ce3+ ion inter-configuration luminescence presumes the simultaneous presence of different excitation mechanisms. The charge transfer excitation mechanism of the doping ion luminescence naturally appears from the fact, that heterovalent Ce ions have a high cross section of hole capture. Another mechanism of scintillation, which is defined as an energy transfer excitation mechanism, originates in crystals from sensitizing of an activator luminescence by the intrinsic luminescence centers. Numerous compounds of rare earth aluminates and silicates show a high light yield scintillation due to combined contribution of both mechanisms. Here we discuss the luminescence excitation mechanisms and scintillation properties of known and new Sn and Ge based compounds doped with Ce. Sn and Ge ions allow to construct many compounds which are isostructural to silicates and aluminates. The factors which influence the energy transfer efficiency in their oxides have been considered.

EuS/Co multilayers are hybrid structures composed of a model ferromagnetic semiconductor EuS (Curie temperature Tc=16.5 K) and a ferromagnetic transition metal Co. Recent investigations of these multilayers revealed variety of important spintronic effects, such as an antiferromagnetic interlayer coupling in EuS/Co bilayers [1] and a very efficient spin filtering by EuS electron barrier in Al/EuS/Co tunneling structures [2]. These effects are expected to originate from the exchange interactions across EuSCo interface. In previous studies, polycrystalline or amorphous EuS/Co multilayers were grown on glass or on Si substrate with Pt/Co metallic buffer layer. In this work, we exploit the technological method developed for the epitaxial growth of EuS/PbS multilayers on KCl and BaF2 substrates, in order to study the magnetic properties of EuS/Co multilayers with monocrystalline EuS layer. EuS/Co/EuS trilayers and Co/EuS bilayers were grown on cleaved KCl (001) and BaF2 (111) substrates using high vacuum deposition technique employing electron guns for Co and EuS. Epitaxial 20-60 nm thick PbS buffer layer was deposited on the substrates from heated tungsten boat. The layer thickness covered the range 35-55 A for EuS and 40-250 A for Co. The structural properties of the layers were examined by xray diffraction method revealing monocrystalline PbS buffer and bottom EuS layer. Co and top EuS layers are expected to be polycrystalline. Magnetic properties of the layers were examined using magneto-optical Kerr (MOKE) and superconductor (SQUID) magnetometry techniques. In the case of MOKE experiments, the linearly polarized light from He-Ne laser was used in longitudinal MOKE geometry. Measurements of magnetic hysteresis loops were performed in temperature range T = 4-250 K and in external magnetic fields up to 2 kOe applied in the plane of the multilayer. All the investigated multilayers showed ferromagnetic properties at room temperature due to Co layer with the ferromagnetic transition in EuS layer clearly marked upon cooling below 16 K. In EuS/Co/EuS trilayers grown on KCl substrate the antiferromagnetic alignment of magnetization vectors of Co and EuS layers was experimentally observed as a characteristic low field plateau on magnetic hysteresis loops and a decrease of multilayer magnetization below 16 K. In contrast, no interlayer coupling was found in multilayers grown on BaF2 substrate. In Co/EuS bilayers, the characteristic temperature dependent shift of the magnetic hysteresis loops was found indicating the well known exchange bias effect. We assign this experimental finding to the exchange coupling between Co layer and an ultrathin (about 2 nm) top antiferromagnetic CoO layer known to spontaneously form on Co layers in the air.

Lutetium Yttrium Perovskite - (Lux - Y1-x)AlO3: Ce, LuYAP:Ce - is a cerium doped scintillation crystal that offers high light yield and high density. LuYAP:Ce with 70% lutetium content in (Lu-Y) system has been applied for medical imaging. Recently volume crystals with good transparency in the spectral range of scintillation have been obtained. It made possible detailed test of the material for well logging application. A unique combination of the parameters: high stopping power, fast and bright scintillation, light yield increase at high temperature makes them attractive for gamma-ray detection in a wide range of temperatures. Evaluation performance test of (Lu0.7 -Y0.3)AIO3: Ce scintillation crystal detector and widely used Nal(Tl), BGO and GSO crystal based detectors of the same size thetas 18 times 60 mm3 has been performed. All crystals were assembled in aluminium case with light reflective material and attached to a high temperature PMTs. It was found that (Lu0.7-Y0.3)AlO3:Ce based detector exhibits the most impressive set of operational characteristics: highest detection efficiency in integral and spectrometric gamma- and n-gamma well logging, excellent stability of the detector response with clear tendency to increase with temperature raise, stable signal-to-noise ratio in the temperature range 25 degC - 175 degC and high resistance to neutron activation. Shock and vibration tests also showed good mechanical stability of the material. Details of the tests and forthcoming application of the scintillator in well-logging are discussed.

We have studied the performance of recently developed solid state photomultipliers (SSPMs) with 2.1times2.1 mm2 sensitive area as a readout for small LSO, (Lu-Y)AP:Ce and PWO-II scintillator crystals. The SSPM is based on the p+-p-n+ structure which was optimized for blue/UV light detection. It operates at a gain of >105 and shows >25% photon detection efficiency in the 380-600 nm spectral range. Energy and timing spectra were measured using a 22Na gamma source. Energy resolutions of 13%, 25% and 50% FWHM were measured for 511 keV gammas with the LSO, (Lu-Y)AP:Ce and PWO-II scintillator crystals respectively. A coincidence timing resolution of 710 ps (FWHM) was measured between two identical LSO+SSPM modules.

The method of direct deposition of carbon and silicon ions was used for preparation of nanocrystalline silicon carbide films. The deposition energy of carbon and silicon ions was 90 eV. The effect of substrate temperature in the range of 500–1150 °C on the structure of SiC films was studied by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD). According to XPS data, the films contained heterobonded Si–C atoms and homobonded Si–Si and C–C atoms, the relation between which varied as the function of substrate temperature. The data of XRD showed a noticeable growth of a nanocrystalline phase of cubic silicon carbide in the films at a temperature of about 700 °C. The content of 3C–SiC nanocrystalline phase reached 80 at.% at 950 °C. There was an established change from cubic polytype to rhombohedral polytype of silicon carbide α-SiC–21R at a substrate temperature higher than 1000 °C. The size of SiC crystal grains depended on the substrate temperature and changed from 4–5 up to 8–10 nm over the range of 700–950 °C. Besides, silicon unbonded with carbon also crystallized in nanocrystalline form with similar sizes of crystal grains. A possible model of the change of the polytypic composition of SiC film under the conditions of direct ion deposition was discussed.

Antiferromagnetic interlayer coupling between ferromagnetic layers of EuS via nonmagnetic PbS spacer layer was experimentally studied in EuS– PbS wedge multilayers grown on KCl (001) substrates with EuS thickness of 6 nm and PbS thickness varying in the wedges in the range 0.3–6 nm (i.e. n = 1−20 monolayers). Measurements of magnetic hysteresis loops of EuS–PbS multilayers performed in the temperature range 5–30 K by superconducting (SQUID) and magneto-optical magnetometers revealed a rapid increase in saturation magnetic field in multilayers with PbS spacer thinner than about 1.5 nm. It shows a monotonic increase in interlayer coupling strength with a decreasing PbS spacer thickness, in qualitative agreement with 1/2 dependence predicted theoretically for semiconductor magnetic superlattices.