Showing papers by "Martin Nikl published in 2007"
TL;DR: In this article, the micro-pulling-down (μ-PD) method is used to grow shape and/or device-size crystals from the melt using a single step process.
180 citations
TL;DR: In this article, thermal stimulated luminescence (TSL) glow curves and emission spectra were studied in undoped and Ce-doped single crystals by wavelength resolved TSL measurements in the $10\char21{}310\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ range.
Abstract: Thermally stimulated luminescence (TSL) glow curves and emission spectra were studied in undoped and Ce-doped ${\mathrm{Lu}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$ single crystals by wavelength resolved TSL measurements in the $10\char21{}310\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ temperature range. Isothermal phosphorescence measurements in the $10\char21{}100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ range were also performed, which point to the existence of a tunneling-driven radiative recombination process. These processes can explain the presence and time-dependence of the submicrosecond slow decay component in the scintillation decay. Electron paramagnetic resonance experiments suggest the presence of ${\mathrm{Lu}}_{\mathrm{Al}}$ defects in the vicinity of ${\mathrm{Ce}}^{3+}$ ions, which are the most probable electron and hole traps participating in the tunneling-driven radiative recombination process.
173 citations
TL;DR: In this paper, the authors used various techniques to study optical and scintillation properties of Ce-doped yttrium aluminum garnet, Y 3 Al 5 O 12 (YAG:Ce), in the form of a high-quality industrial single crystal.
165 citations
TL;DR: In this paper, the intrinsic emission of complex oxides with garnet structure was studied by means of the analyses of the time-resolved luminescence spectra and decay kinetic for single crystals (SC) and single-crystalline films (SCF) of Y3Al5O12 (YAG) and Lu3Al 5O12(LuAG) garnets under excitation by the pulse X-ray and synchrotron radiation at 8-300 K.
Abstract: Intrinsic emission of complex oxides with garnet structure was studied by means of the analyses of the time-resolved luminescence spectra and decay kinetic for single crystals (SC) and single-crystalline films (SCF) of Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) garnets under excitation by the pulse X-ray and synchrotron radiation at 8–300 K. YAG and LuAG SC and SCF are characterized by significantly different concentration of the YAl and LuAl antisite defects (AD) due to the substantial difference in the conditions of their crystallization. For this reason, LuAG and YAG SC and SCF are very useful model objects for the study of nature of the intrinsic emission of these oxides, consisting of the excitons and AD luminescence. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
150 citations
TL;DR: In this article, the luminescence and scintillation properties of single crystalline films (SCF) of Ce-and Pr-doped Y 3 Al 5 O 12 (YAG)- garnets were analyzed and compared with their bulk single crystal (SC) analogues.
89 citations
TL;DR: In this article, the steadystate and time-resolved emission and excitation spectra and luminescence decay kinetics were studied under excitation in the 2.5-15 eV energy range for undoped and Ce3+-doped Lu3Al5O12 (LuAG) single-crystalline films grown by liquid phase epitaxy method from the PbO-based flux.
72 citations
TL;DR: Nikl et al. as mentioned in this paper measured the optical absorption, luminescence, and scintillation characteristics of Lu3Al5O12 and compared with an analogous high quality single crystal.
Abstract: Optical absorption, luminescence, and scintillation characteristics of Lu3Al5O12:Ce optical ceramics were measured and compared with an analogous high quality single crystal. Optical absorption of the former shows an additional light scattering loss due to nanovoids and/or refraction index inhomogeneities. Even though radioluminescence intensity of the optical ceramics prepared by a coprecipitation route exceeds that of single crystal, its scintillation light yield is lower due to the charge carrier retrapping in the process of energy transfer towards the Ce3+ emission centers. Retrapping processes are evidenced by thermoluminescence measurements below room temperature. Lu3Al5O12:Ce optical ceramics does not show the presence of the LuAl antisite defects which decreases the scintillation figure of merit in single crystals grown from the melt [M. Nikl, Phys. Status Solidi A 202, 201 (2005)]. Furthermore, using the ceramic technology, one can achieve both the homogeneous doping and higher Ce concentration. ...
66 citations
TL;DR: In this article, the luminescence properties and the energy transfer from host to Ce 3 + ions are analyzed in single crystalline films (SCF) of YAlO3:Ce (YAP: Ce), Y 1 - x Lu x AP :Ce, YLuAP:Ced and LuAlO 3:Ces (LuAP):Ce) perovskites in comparison with their single crystal (SC) analogues using the time-resolved luminecence spectroscopy under synchrotron radiation excitation.
53 citations
TL;DR: In this article, the absorption and cathodoluminescence spectra of single crystalline films (SCF) of Y 3 Al 5 O 12 : Bi garnet depending on Bi concentration were analyzed.
46 citations
TL;DR: In this article, it was shown that in pure and Ce-doped LPE films, the Ce 3 + impurity substitutes only for Lu 3 + sites in the trivalent charge state at the Al octahedral sites.
45 citations
TL;DR: In this article, a hybrid photomultiplier was used to measure scintillation response of the YAG:Ce and YAG films using 239Pu alpha particle source.
TL;DR: In this paper, the authors investigated the green emission properties of two green emission bands, G(I) and G(II), and their origin were investigated within 0.4-300-k under photoexcitation in the 3.4 -6.0-eV energy range for undoped and Mo 6+ -doped PbWO 4 crystals with different concentrations of impurity and intrinsic defects, grown by different methods and annealed at different conditions.
TL;DR: In this paper, the time development of a Nphels/MeV photoelectron yield of various Ce and Pr-doped inorganic crystals (mainly garnets, perovskites and silicates) was studied in detail.
Abstract: Time development of a Nphels/MeV photoelectron yield of various Ce and Pr-doped inorganic crystals (mainly garnets, perovskites and silicates) was studied in detail. Slow scintillation decay components influence time dependence, especially at those scintillators containing Lu as lattice ions where an increase of Nphels per 1 MeV in the time span 0.25–5 µs is more than 50%. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: Using the micro-pulling-down method, Pr 3+ -doped YAlO 3 single crystals were grown and their optical and luminescence properties were investigated within 80-300 K as discussed by the authors.
TL;DR: In this paper, electron paramagnetic resonance (EPR) and thermostimulated luminescence (TSL) experiments were performed on single crystals of perovskite and garnet structures.
Abstract: Electron and hole trapping phenomena below room temperature were studied by simultaneous use of electron paramagnetic resonance (EPR) and thermostimulated luminescence (TSL) experiments in Ce-doped YAlO 3 , Y 3 Al 5 O 12 and Lu 3 Al 5 O 12 single crystals. Charge-carrier trapping associated with O - centers and antisite Y(Lu) Al defects in perovskite and garnet structures, respectively, was evidenced by EPR and associated with the dominant TSL peaks. Existence of F + centers was proved by EPR in YAlO 3 . A Ce 3+ ion at the Al site and spatially correlated Ce Lu and Lu Al centers were evidenced in Lu 3 Al 5 O 12 by the same method. Spatial correlation of the latter two centers is further supported by the associated tunneling-driven radiative recombination process evidenced by phosphorescence decay.
TL;DR: LiCaAlF 6 (LiCAF) crystals doped with two different rare earth (RE) ions (europium and cerium) have been investigated as potential new dosimetric materials.
TL;DR: In this article, the binding energy of the Zn 2P electron and the lower kinetic energy of Auger Zn L 3 M 4, 5 M 4, 5, 5 electron were obtained on selected samples to have information about Zn-O-Si bonding in the glass.
TL;DR: In this paper, single crystals with nominal composition of (Pr001,Lu099)3(Gax,Al1-x)5O12 (Pr:LuGAG) were grown by the micro-pulling-down (µ-PD) method with RF heating and their luminescence properties were characterized Transparent and crack free crystals that were slightly yellowish green were obtained Lattice constants and densities systematically increased with increasing of Ga concentration.
Abstract: Single crystals with the nominal composition of (Pr001,Lu099)3(Gax,Al1-x)5O12 (Pr:LuGAG) were grown by the micro-pulling-down (µ-PD) method with RF heating and their luminescence properties were characterized Transparent and crack free crystals that were slightly yellowish green were obtained Lattice constants and densities systematically increased with increasing of Ga concentration The luminescence properties of Pr:LuGAG were characterized by photoluminescence spectra and decays, radioluminescence spectra and light yield measurements 5d–4f luminescence was observed for the x≤06 samples It was found that the 5d–4f emission of Pr3+ is quenched only slightly up to x≤04 whereas density systematically increased in the range of 0≤x≤10
TL;DR: In this paper, single crystals of PbWO 4 and Lu 3 Al 5 O 12 -based scintillators were studied by correlated electron paramagnetic resonance and thermally stimulated luminescence experiments.
04 May 2007
TL;DR: In this paper, a single crystal of PbWO 4, Ce-doped YAlO 3 and Ce(Pr)-doped y(Lu) 3 Al 5 O 12 were irradiated by 60 Co and doses ranging between 1-500 Gy.
Abstract: Gamma radiation induced absorption processes of various scintillating materials were studied at room temperature.
Single crystal of PbWO 4 , Ce-doped YAlO 3 and Ce(Pr)-doped Y(Lu) 3 Al 5 O 12 were irradiated by 60 Co and doses ranging
between 1-500 Gy. Broad induced absorption spectra obtained were decomposed into separate Gaussian components and
tentatively ascribed to specific color centres. Supporting thermoluminescence and electron paramagnetic resonance
experiments were performed to reveal the nature of charge carrier traps. The influence of codoping by aliovalent ions is
also shown and discussed.
TL;DR: In this article, the steady state and time-resolved emission and excitation spectra as well as defects creation spectra were studied for Pr3+-doped Y3Al5O12 (YAG) and Lu3Al 5O12(LuAG) single crystals at 11-300k in the 2-12eV energy range.
TL;DR: In this article, the intrinsic emission of complex oxides with perovskite structure was analyzed in the undoped single crystal (SC) and single crystalline films (SCF) of YAlO3 (YAP) using the time-resolved luminescence spectroscopy under excitation by synchrotron radiation.
Abstract: Intrinsic emission of complex oxides with perovskite structure was analyzed in the undoped single crystal (SC) and single crystalline films (SCF) of YAlO3 (YAP) using the time-resolved luminescence spectroscopy under excitation by synchrotron radiation. In contrast to bulk SC the YAP SCF are characterized by much lower concentration of YAl antisite and vacancy-type defects, which contribute to the intrinsic emission of YAP SC. Such a difference comes mainly from much lower temperature of the film growth using the Liquid Phase Epitaxy. For this reason, comparison of YAP SC and SCF appears very useful to study the nature of the intrinsic emission of perovskites consisting mainly of the exciton and defect-related luminescence. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, the time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 160-300 K for undoped and Mo-doped PbWO4 crystals under XeCl (4.02 eV), N2 (3.67 eV) and KrF (5.0 eV).
Abstract: Time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 160-300 K for undoped and Mo-doped PbWO4 crystals under XeCl (4.02 eV), N2 (3.67 eV) and KrF (5.0 eV) pulsed excimer laser excitation. The G(II) emission was found to be responsible for the slow (µs-ms) luminescence decay. Under excitation or after irradiation in the exciton region (Eexc = 4.02 eV), this emission accompanies the monomolecular tunneling recombination in genetic pairs of electron and hole centers produced at the photo-thermally stimulated decay of localized excitons, which occurs without release of free charge carriers. Under excitation or after irradiation in the host lattice (Eexc = 5.0 eV) and defect-related (Eexc = 3.67 eV) regions, the bimolecular tunneling recombination takes place in chaotic pairs of the electron and hole centers created at the trapping of optically released free charge carriers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, the impurity related defect states in pure and Sc-doped lutetium aluminum garnet Lu3Al5O12 (LuAG) were analyzed using the electron spin resonance (ESR) method.
TL;DR: In this article, the luminescence and defects creation processes were studied at 4.2-300-k under excitation in the 3.0-10.5-eV energy range for an YAlO3:Ce crystal with very low concentration of Ce3+ ions.
TL;DR: A brief review of recent results obtained at systematic study of the luminescence and photo-thermally stimulated defect creation processes in various undoped and doped PbWO 4 crystals is presented in this paper.
TL;DR: In this article, Czochralski-grown YAG:Pr single crystal was investigated as a potential novel scintillator material and its optical properties including photoluminescence, radioluminecence, scintillation decay, radiation damage and thermolumine emission were measured.
Abstract: We investigated Czochralski-grown YAG:Pr single crystal as a potential novel scintillator. Optical characteristics including photoluminescence, radioluminescence, scintillation decay, radiation damage and thermoluminescence were measured. Their dependence on the dopant concentration was studied. The radiation damage results show that with increasing concentration of Pr the radiation damage reduces. Thermoluminescence above room temperature shows the dominant glow curve peak around 250 °C. Comparing to YAG:Ce scintillator an advantage of YAG:Pr is its much faster scintillation decay (16-17 ns at room temperature) and an absence of slow components in the decay. Therefore YAG:Pr appears as potentially interesting scintillator material. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: Using the micro-pulling-down method, Pr3+-doped Y2SiO5 single crystals have been grown and their optical and luminescence properties have been investigated as discussed by the authors.
TL;DR: In this paper, the steady state and time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 4.2-350 K under excitation in the 2.5-15 eV energy range for the undoped and Ce3+-doped Lu3Al5O12 (LuAG) single crystalline films grown by Liquid Phase Epitaxy method.
Abstract: Steady-state and time-resolved emission and excitation spectra and luminescence decay kinetics were studied at 4.2-350 K under excitation in the 2.5-15 eV energy range for the undoped and Ce3+-doped Lu3Al5O12 (LuAG) single crystalline films grown by Liquid Phase Epitaxy method. The spectral bands arising from the single Pb2+-based centers were identified. Competition between Pb2+ and Ce3+ ions in the processes of energy transfer from the LuAG crystal lattice was evidenced. Due to overlap of the 3.61 eV emission band of Pb2+ centers with the 3.6 eV absorption band of Ce3+ centers, an effective energy transfer from Pb2+ ions to Ce3+ ions occurs, resulting in the appearance of slower component in the luminescence decay kinetics of Ce3+ centers and decrease of the Ce3+-related luminescence intensity. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, the processes of luminescence and photo-thermally stimulated defect creation were studied at 80-350 K under selective UV irradiation in the 5.0-3.5 eV energy range for as-grown and 600 °C air annealed PbWO4 crystals (grown in both cases by the Bridgman method).
Abstract: Lead tungstate crystals grown by the Bridgman method are oxygen deficient. Therefore they are suitable objects for the detailed study of various oxygen vacancy-related defects. The processes of luminescence and photo-thermally stimulated defect creation were studied at 80–350 K under selective UV irradiation in the 5.0–3.5 eV energy range for as-grown and 600 °C air annealed PbWO4 crystals (grown in both cases by the Bridgman method). The creation of defects reveals itself in the appearance of thermally stimulated luminescence (TSL) peaks and electron spin resonance signals. Dependences of the TSL peak intensity on the irradiation energy, temperature and duration were investigated. In the crystals studied the observed characteristics are explained by the presence of excitons localized at oxygen-deficient anion complexes of different types (WO3, WO2, WO) and the photo-thermally stimulated decay of these excitons into electron and hole centres. The origin of these centres and their creation processes are discussed.