Photon cutting for excitation of Er 3+ ions in SiO 2 sensitized by Si quantum dots
Résumé
We present evidence of a mechanism for the indirect excitation of Er 3+ ions in a SiO 2 matrix sensitized with Si quantum dots (SiQDs). The proposed process enables the simultaneous and rapid excitation of two proximal Er 3+ ions upon absorption of a single high-energy photon in a SiQD. The experimental evidence leading to the identification of this energy-transfer path is obtained from investigations of the photoluminescence quantum yield of two Er-related emission bands at 1.54 and 0.98 μm in SiO 2 layers doped with small (∼2-nm-diam) SiQDs and a high concentration of Er 3+ ions, prepared by sputtering on hot substrates. In contrast to the previously considered mechanisms for the indirect excitation of Er 3+ ions in SiO 2 , this excitation process offers an advantage of efficient suppression of the most important channels of nonradiative deexcitation—the Auger energy transfer to free carriers as well as the so-called energy back transfer of excitation reversal. This feature revives hopes for the practical application of Er-doped SiO 2 sensitized by SiQDs.
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