Sensitization of the 1.54 mu m luminescence of Er3+ in SiO2 films by Yb and Si-nanocrystals

A systematic study of excitation of the 4f-4f luminesence of Er3+ ions near 1.5 mum in SiO2 layers codoped with Yb and containing Si-nanocrystals (nc- Si) is presented. Layers of SiO2 were implanted with Er+ and Yb+ ions at th e energies of 800 and 830 keV, respectively, at a wide range of doses (0.5- 4.0 x 10(15) cm(-2)). Photoluminescence (PL) and PL excitation spectroscopy were applied to study excitation of Er3+ ions. The Yb3+ ions were found to play a key role in sensitizing the PL of Er3+ for pump wavelengths similar to 500 nm and 1 mum. Models of sensitization processes involving energy tr ansfer from Yb-centers are discussed. Silicon nanocrystals were produced by high dose Si implantation into SiO2 (excess Si contents similar to 7%) fol lowed by annealing at 1100 degreesC. An evidence is presented that transfer of energy from nc-Si is not the dominant mechanisms of excitation of Er3ions. Defect mediated mechanisms seem to be more efficient. It is also foun d that excess Si in SiO2 prevents clustering of ran earth atoms. (C) 2001 E lsevier Science B.V. All rights reserved.