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ALT' M' LS-P-11
LASER SYSTEMS AND MATERIALS
Photoluminescence of SrF2:Eu powders after annealing in CH4/H2 microwave plasma
I. Tiazhelov1, A. Martyanov1, V. Sedov1, K. Boldyrev2, A. Drobysheva1, Yu. Ermakova1, A. Alexandrov1, V.
Voronov1, S. Kuznetsov1
1- Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow 2- Institute of Spectroscopy of the Russian Academy of Sciences, Troitsk, Moscow Main author email address: tiazhelov@rambler.ru
In the last decade, high-power X-ray sources have been developed: synchrotrons and XFEL-lasers [1]. Materials used for visualization of intense radiation (for example, LiF) degrade rapidly due to the low thermal conductivity (~4 W/(m*K) at ambient conditions), weak heat dissipation and sharp local heating occur [2].
Radiation-resistant materials for use in X-ray imaging devices must have (i) high thermal conductivity, (ii) intense X-ray luminescence, (iii) chemical stability. Diamond has record-breaking physical and chemical properties such as the highest thermal conductivity among bulk materials (~2100 W/(m*K) at ambient conditions), transparent in wide spectral range, X-ray resistant, and chemically inert. Europium ions embedded in the crystal lattice of some compounds are capable of causing intense luminescence, and the wavelength of the emitted light depends on the degree of oxidation of the europium ions and symmetry of optical center. Previously, in our paper [3], it was shown that diamond-matrix composites with embedded rare-earth particles can exhibit bright X-ray luminescence in the visible range.
In this work, we studied the impact effect of microwave plasma on the optical properties of SrF2:Eu powders. SrF2:Eu nanopowders were obtained by precipitation from aqueous solutions followed by heat treatment at a temperature of 600°C. A series of powder on substrates (100) of oriented single-crystal silicon was annealing in methane-hydrogen plasma at a temperature of 880°C for 2, 6, 10, and 30 min and in pure hydrogen plasma at a temperature of 840°C for 10 min. Exposure to any plasma for even 2 minutes changes the photoluminescence spectrum of the samples (Fig. 1).
500 550 600 650 700 750 800 Wavelength (nm)
Fig. 1. Typical photoluminescence spectra before (1) and after (2) annealing of samples in plasma upon excitation at a wavelength of 473 nm.
As a result, it was found that the action of methane-hydrogen plasma on SrF2:Eu powders leads to a radically change in the photoluminescence spectrum: instead of a set of narrow lines, broadband photoluminescence is observed in the range of 480-750 nm with a maximum at about 580 nm. A change in the luminescence spectrum may arise from set of reasons such as partially reduction of Eu3+ to Eu2+ or occurrence of defects on the particles surface.
The work was supported by the Russian Science Foundation, Grant No. 22-13-00401.
[1] T. Pikuz. et. al., 3D visualization of XFEL beam focusing properties using LiF crystal X-ray detector, Scientific Reports, vol. 5, pp. 1-10, (2015).
[2] T. Kurobori, et. al., A comparative study of optical and radiative characteristics of X-ray-induced luminescent defects in Ag-doped glass and LiF thin films and their applications in 2-D imaging, Nuclear Instruments and Methods in Physics Research, vol. 326, pp. 76-80, (2014).
[3] S. Kuznetsov, et. al., Cerium-doped gadolinium-scandium-aluminum garnet powders: Synthesis and use in X-ray luminescent diamond composites, Ceramics International, vol. 48, pp. 12962-12970, (2022).
