Spectroscopy of condensed matter

Excitation mechanism of pulsed cathodoluminescence of cerium in yttrium-aluminum garnet

V. I. Solomonov, V. V. Lisenkov, A. V. Spirina, A. S. Makarova

Institute of Electrophysics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia

Abstract: The pulsed cathodoluminescence of a cerium ion in ceramic samples of yttrium aluminum garnet with a ceria content of 0.1, 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0 at.% was studied. These samples were irradiated in air at room temperature with a 2-ns-duration electron beam with an average electron energy of 170 keV and a current density of 130 A/cm$^2$. It enables to simulate the external ionizing radiation for scintillators. Two broad luminescence bands were observed at 570 nm and at 350 nm, being the results of the Ce$^{3+}$ ion $d$–$f$ transition and the recombination of a self-trapped exciton, respectively. The cerium luminescence band center shifts to the long wavelength region with an increase in the content of ceria. It is found that the intensity decay of the cerium band, measured for each concentration at a wavelength of 570 nm, is characterized by two maxima in the nanosecond ($t_{m1}\approx$ 3 ns) and microsecond ($t_{m2}\approx$ 1.3 $\mu$s) time intervals. The first maximum is shown to be formed due to, firstly, the excitation of Ce$^{3+}$ $d$-levels by secondary electrons generated by beam electrons and, secondly, spontaneous emission with a characteristic time of $\tau_s$ = 100 $\pm$ 10 ns. The second maximum arises when the excited Ce$^{3+}$ is formed during the recombination of Ce$^{2+}$ and Ce$^{4+}$ ions produced by the electron beam. After the second maximum, the intensity decay of the band is described by a hyperbolic law with a characteristic time of 30–75 $\mu$s, depending on the content of cerium ions, and the light sum of this recombination luminescence is 60% of the total luminescence light sum of the band. The luminescence intensity decay of the band at 350 nm is monotonic and a characteristic decay time is 63.7 ns for a sample with a ceria content of 0.1 at.% and about 10.5 ns for samples with a ceria content of 0.5–5 at.%.

Keywords: pulsed cathodoluminescence, cerium, yttrium-aluminum garnet, kinetics, rise, decay, characteristic times.

Received: 25.12.2024
Revised: 25.12.2024
Accepted: 06.02.2025

DOI: 10.61011/OS.2025.02.59965.6934-24

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