Energy transfer from the host to Er^3+ dopants in semiconductor SnO2 nanocrystals segregated in sol–gel silica glasses

Undoped and Er^3+-doped glass–ceramics of composition (100–x)SiO2–xSnO2, with x = 5 or 10 and with 0.4 or 0.8 mol% of Er3+ ions, were synthesised by thermal treatment of precursor sol– gel glasses. Structural studies were developed by XRay Diffraction. Wide band gap SnO2 semiconductor quantum-dots embedded in the insulator SiO2 glass are obtained. The mean radius of the SnO2 nanocrystals, ranging from 2 to 3.2 nm, is comparable to the exciton Bohr radius. The luminescence properties have been analysed as a function of sample composition and thermal treatment. The results show that Er^3+ ions are partially partitioned into the nanocrystalline phase. An efficient UV excitation of the Er^3+ ions by energy transfer from the SnO2 nanocrystal host is observed. The Er^3+ ions located in the SnO2 nanocrystals are selectively excited by this energy transfer mechanism. On the other hand, emission from the Er^3+ ions remaining in the silica glassy phase is obtained by direct excitation of these ions.