LUMINESCENCE OF ACTIVATED THIN Bi4Ge3O12 FILMS

Oleh Bordun, I. Bordun, I. Kukharskyy, I. Medvid, I. Kofliuk

Abstract


The luminescence spectra of Bi4Ge3O12 (BGO) thin films activated with Si, Mn, Tb, and Eu under X-ray, cathodic, and photoexcitation have been studied. BGO films (thickness 0.5–1.5 μm) activated with Si, Mn, Eu, Tb and their combination were obtained by the method of discrete evaporation in vacuum on fused quartz substrates. The content of activators in different samples varied in the range of 0.1–5.0 mol%. After sputtering, the films were annealed in air at 8500C. X-ray diffraction studies have shown the presence of a polycrystalline structure of the films with a predominant orientation in the (211), (310), and (312) planes.

It was found that the luminescence spectra of the activated films, as well as of pure BGO films under different types of excitations, consist of three bands with maxima at 2.7, 2.4, and 2.05 eV. The decomposition of the spectra into individual bands was carried out by the Alentsev-Fock method using a set of luminescence spectra under different types of excitations. It is shown that the introduction of the activator leads to a relative increase in the intensity of all three luminescence bands, but this is most effective for the band with a maximum of 2.4 eV. It should also be noted that at an activator concentration exceeding 2 mol%, a concentration quenching of the luminescence intensity is observed.

It has been found that under laser excitation in BGO thin films activated with Tb3+ and Eu3+ ions of rare earth metals, the luminescence spectra are caused by electronic transitions inside the activator ions. Analyzing the real point symmetry of the Bi3+ environment, it is assumed that in the process of activation of BGO thin films, the rare earth ions Tb3+ and Eu3+, which appear in the luminescence, replace Bi3+ ions. It is proposed that this luminescence is most likely due to the direct excitation of activator ions, since the excitation energy of the nitrogen laser ЛГИ-21 falls within the excitation region of the studied rare-earth activator ions. The interpretation of the selected luminescence bands is considered.

Key words: bismuth orthogermanate, activator, luminescence spectrum, cathodoluminescence, X-ray luminescence.


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DOI: http://dx.doi.org/10.30970/eli.26.9

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