Yuriy Zorenko

Single Crystalline Film Scintillators Based on the Orthosilicate, Perovskite and Garnet Compounds

This work reviews our R&D of new types of scintillating screens based on the single crystalline films (SCF) of Lu,Y orthosilicate, perovskite and garnet compounds grown by the liquid phase epitaxy method. The scintillation and luminescent properties of the following types of SCF scintillators are considered in this work: (i) Ce-doped SCF of Y,Lu-based orthosilicates and perovskites with the Ce3+ emission in the 325-600 nm and 360-370 nm ranges with a decay time of 20-33 ns and 16-17 ns, respectively; (ii) Ce,Tb doped SCF of Y,Lu-based orthosilicates and perovskites with the simultaneous Ce3+ and Tb3+ emission in the blue or UV and green spectral ranges, respectively; (iii) Sc3+ doped SCF of Y-Lu-Al-garnets, emitting in the 290-400 nm range due to formation of the ScY,Lu and ScAl centers with a decay time of the order of hundreds of nanoseconds.

Epitaxial growth of gadolinium and lutetium-based aluminum perovskite thin films for X-ray micro-imaging applications

Our work is related to the liquid phase epitaxy-based development of new scintillating screens for high-resolution X-ray imaging. We successfully grew undoped and Tb, Eu and Ce-doped GdAlO3 as well as GdxLu1−xAlO3 single crystalline films on YAlO3 substrates. We studied crystallization conditions as a function of melt composition, growth temperature and lattice mismatch between the film and the substrate. The film composition was measured by using an electron microprobe and the morphology of the film surface was studied by scanning electron microscopy. X-Ray diffraction was used to characterize the crystal structure and the mismatch between the film and the substrate. In addition, the light yield of the Eu3+-doped films, as well as the obtained spatial resolution show that GdxLu1−xAlO3 may advantageously compete with existing thin film scintillators in particular energy ranges.

Scintillating Screens for Micro-Imaging Based on the Ce-Tb Doped LuAP Single Crystal Films

Single Crystal Film (SCF) scintillators are key-components of todays high-resolution 2D X-ray detectors used at synchrotrons for applications such as X-ray Radiography, Computed Tomography (CT), laminography, full-field XANES, and topography. Due to its high density and effective atomic number, LuAlO3 (LuAP) perovskite has a great potential to replace or complement the currently used Eu-doped Gd3Ga5O12 (GGG:Eu) and Tb-doped Lu2SiO5 (LSO:Tb) SCFs. In this article we present the growth of LuAP single crystalline films on undoped YAlO3 (YAP) by the vertical dipping isothermal Liquid Phase Epitaxy (LPE) growth method. For the comparison of the light output of Ce and Tb doped LuAP SCF screens both cathodoluminescence (CL) and X-ray excited luminescence (RL) measurements were used. For investigations of Ce-Tb energy transfer in the afore mentioned oxide hosts, in addition to using traditional spectroscopic methods, we made time-resolved luminescent spectroscopy of Ce-Tb doped LuAP SCFs under excitation by pulsed synchrotron radiation at the Superlumi station (HASYLAB at DESY). Recently we have demonstrated the strong quenching influence of Pb2+ flux related impurity on the Ce3+ emission in the Ce-doped LuAP SCF screens. However our present investigation shows that Tb-doped LuAP SCFs are efficient X-ray scintillators, whose light output can be significantly increased by co-doping with Ce3+ ions. Namely, we demonstrate the efficient Ce→ Tb energy transfer in LuAP:Tb,Ce SCFs. Finally, as-grown LuAP:Tb and LuAP:Tb,Ce films were evaluated for high-resolution X-ray imaging using a spatial resolution target at the European Synchrotron Radiation Facility (ESRF), and displayed promising results.

Thermoluminescent Properties of Undoped and Ce-Doped Lutetium Orthosilicate and Yttrium Orthosilicate Single Crystals and Single Crystalline Films Scintillators

In this work the comparative analysis of thermoluminescent properties of undoped and Ce-doped single crystals (SC) and single crystalline films (SCF) of Lu₂SiO₅ (LSO) and Y₂SiO₅ (YSO) orthosilicates were performed. The SC samples were prepared with the Czochralski method, and SCF were grown by the liquid phase epitaxy technique. We show that such different methods of material preparation resulted in different thermoluminescent properties of undoped and Ce³⁺ doped LSO and YSO SC and SCF caused by the presence host defects (first of all, oxygen vacancies) as trapping centers in SC and formation of Pb²⁺-Ce⁴⁺ pair centers in SCF.

Scintillating Screens Based on the Single Crystalline Films of Multicomponent Garnets: New Achievements and Possibilities

The paper is dedicated to development of the novel scintillating screens based on single crystalline films (SCF) of Ce doped Lu_{3 - x}Tb_xAl_{5 - y}GayO₁₂ multicomponent garnets at x = 2 - 3 and y = 0 - 2.5 onto Y₃Al₅O₁₂ (YAG) and Gd₃Al_2.5Ga_2.5O₁₂ (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 Tb₃Al_2.5Ga_2.5O₁₂: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.

Epitaxial Growth of LuAG:Ce and LuAG:Ce,Pr Films and Their Scintillation Properties

We performed the growth by Liquid Phase Epitaxy (LPE) of Ce and Ce-Pr doped Lu₃Al₅O₁₂ (LuAG) Single Crystalline Films (SCFs) onto LuAG and Y₃Al₅O₁₂ (YAG) substrates. The structural properties of LuAG:Ce and LuAG:Ce,Pr SCFs were examined by X-ray diffraction. The optical properties of the SCFs were studied through cathodoluminescence (CL) spectra, scintillation Light Yield (LY), decay kinetic under <inline-formula> <tex-math notation=LaTeX>

LPE growth and luminescent properties of Ce doped A 2S iO 5 :Ce (A = Lu, Gd, Y) single crystalline films

alpha

TSL properties of A 2 SiO 5 and A 2 SiO 5 :Ce (A=Y, Lu) single crystals and single crystalline films

</tex-math></inline-formula>–particle (Pu²³⁹) excitation, X-ray excited luminescence, thermostimulated luminescence (TSL) and afterglow measurements. The SCFs grown on LuAG substrates displayed good surface quality and structural perfection, whereas the SCFs grown on YAG substrates showed a rough surface and poorer crystalline quality, due to a large lattice mismatch between the film and the substrate (0.82%). Under <inline-formula> <tex-math notation=LaTeX>

Scintillating screens based on the LPE grown Tb3Al5O12:Ce single crystalline films

alpha

Development of scintillating screens based on the single crystalline films of Ce doped (Gd,Y)3(Al,Ga,Sc)5O12 multi-component garnets

</tex-math></inline-formula>-particle excitation, the LY of LuAG:Ce SCF exceeded by 2 times that of the best YAG:Ce SCF sample used as reference. Under X-ray excitation, the LuAG:Ce SCF with optimized Ce concentration showed LY close (77%) to a reference YAG:Ce Single Crystal (SC) scintillator. The afterglow of LuAG:Ce and LuAG:Ce,Pr SCFs was lower (by 1 decade) than that of the tested reference LuAG:Ce SC. However there is not a complete suppression of the afterglow at room temperature (RT), despite the fact that the SCFs present much lower concentration of antisite and vacancy type defects than their SC counterparts. This can be explained by the presence in the films of other trap centers responsible for TSL above RT.