X-ray-excited optical luminescence of erbium-doped semiconductor: site-selective X-ray absorption spectroscopy of an optically active atom

The X-ray-excited optical luminescence (XEOL) of erbium-doped silicon (Si:Er) thin film is observed for the site-selective X-ray absorption spectroscopy (XAS) of an optically active Er atom. In order to achieve the site-selectivity at the atomic level, intense X-ray from an undulator is used for the excitation of Er. Indirect excitation caused by X-ray absorption at Si around Er is investigated, and X-ray induced luminescence independent of the inner-shell excitation of Er is observed. A possible mechanism is proposed, in which the formation of an electron-hole pair in Si and the subsequent transfer of recombination energy excite the valence electron of Er. According to this model, energy back-transfer with phonon absorption is used to suppress the indirect excitation, resulting in the site-selective XAS of Er atom. (C) 2001 Elsevier Science B.V. All rights reserved.