1. WZI seminar 16-04-2003 Si nanocrystals as sensitizers for Er 3+ PL in SiO 2 M. Wojdak Van der Waals - Zeeman Institute, University of Amsterdam Valckenierstraat 65, NL-1018 XE Amsterdam, The Netherlands

2. WZI seminar 16-04-2003 Motivations Why Er 3+ ? Transition of =1.53m is coincident with minimum loses in glass fibers. The lifetime of 1 st excited state can be in the order of milliseconds (SiO 2 ) or s (Si) - possibility of population inversion Why silicon ? Most common electronic material Integration of optoelectronics Possibility of optical or electrical excitation of Er 3+

3. WZI seminar 16-04-2003 Erbium in silicon Excitation pathway in Si:Er VB CB Er 3+ ion host Ar +, Nd:YAG Recombination of e-h pair Er 3+ excitation Radiative decay Optical or electrical excitation Capture at erbium centers PL quenching at room temperature

4. WZI seminar 16-04-2003 Erbium in SiO 2 1535 nm 980 nm 800 nm 650 nm 550 nm 520 nm 490 nm 4 I 11/2 4 I 13/2 4 I 15/2 2 H 11/2 4 S 3/2 4 F 9/2 4 I 9/2 4 F 7/2 Er 3+ Thermal stability of emission Only resonant excitation Excitation cross section is extremely small 2 x 10 -20 cm 2 (W. Miniscalco J. Lightwave Technol. 9, 234, 1991)

5. WZI seminar 16-04-2003 SiO 2 :Si-nc,Er Excitation cross section ~10 -16 cm 2 Nonresonant excitation allowed PL emission in room temperature (SiO 2 host). Er 3+ Si-nc

6. WZI seminar 16-04-2003 Photoluminescence excitation spectra Er 3+ Si-nc 1535 nm 980 nm 800 nm 650 nm 550 nm 520 nm 490 nm 4 I 11/2 4 I 13/2 4 I 15/2 2 H 11/2 4 S 3/2 4 F 9/2 4 I 9/2 4 F 7/2 Er 3+

7. WZI seminar 16-04-2003 Comparison of PL intensity with Ar + laser SiO 2 :Er - excitation cross section ~10 -20 cm 2 (W. Miniscalco J. Lightwave Technol. 9, 234, 1991) SiO 2 :Si-nc,Er - excitation cross section ~10 -16 cm 2 10 4 Ar + laser, exc =514.5nm ROOM TEMP.

8. WZI seminar 16-04-2003 Samples SiO 2 :Er SiO 2 :Er,Si-nc Er concentration: 2.2 × 10 20 cm -3 Er concentration: 2.2 × 10 20 cm -3 Si-nc concentration: 5 × 10 17 - 10 18 cm -3 diameter: 3.4 nm Er 3+ Si-nc Photoluminescence spectra Samples were obtained in collaboration with the group of Prof. Francesco Priolo University of Catania Decay kinetics

9. WZI seminar 16-04-2003 Experimental setup sample PL Variable wavelength 430-650 nm (2.8-1.9 eV) 780-2000 nm (1.6-0.6 eV) Pulse t=5ns, 20Hz OPO or Ar + Excitation of Photoluminescence (PL) Optical Parametric Oscillator (OPO) pumped by Nd:YAG Ar + laser =514.5 nm Detectors PMT Germanium detector Spectrometer Triax 320mm

10. WZI seminar 16-04-2003 The model Rate equation Laser pulse is much shorter than  Population obtained after t Photoluminescence emitted after the pulse is integrated in time: Approximations: When t <<1 When t >>1

11. WZI seminar 16-04-2003 Excitation flux dependence

12. WZI seminar 16-04-2003 Excitation flux dependence

13. WZI seminar 16-04-2003 Excitation flux dependence

14. WZI seminar 16-04-2003 Excitation flux dependence

15. WZI seminar 16-04-2003 Excitation flux dependence

16. WZI seminar 16-04-2003 Excitation flux dependence  = 8.7 x 10 -17 cm 2

17. WZI seminar 16-04-2003 Excitation flux dependence

18. WZI seminar 16-04-2003 Pulsed and continuous excitation Pulsed Continuous =520 nm 30 = 514.5 nm 90 = 488 nm

19. WZI seminar 16-04-2003 Conclusion ~33% ~66% ~0.2% SiO 2 :Si-nc,Er

20. WZI seminar 16-04-2003 M. Forcales, M. Klik, N.Q. Vinh, I. Izeddin, and T. Gregorkiewicz, Van der Waals - Zeeman Institute, Valckenierstraat 65, NL-1018 XE Amsterdam, The Netherlands O. B. Gusev, A.F.Ioffe Physicotechnical Institute, Russian Academy of Science, 194021 St. Petersburg, Russia G. Franzò, D. Pacifici, F. Priolo, INFM and Dipartamento di Fisica e Astronomia, Università di Catania, Corso Italia 57, I-95129 Catania, Italy F. Iacona CNR-IMETEM, Stradale Primosole 50, I-95121 Catania, Italy Acknowledgements Financial support: NWO, ARL-ERO