WZI seminar 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

WZI seminar 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+

WZI seminar 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

WZI seminar Erbium in SiO 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 cm 2 (W. Miniscalco J. Lightwave Technol. 9, 234, 1991)

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

WZI seminar 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+

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

WZI seminar Samples SiO 2 :Er SiO 2 :Er,Si-nc Er concentration: 2.2 × cm -3 Er concentration: 2.2 × cm -3 Si-nc concentration: 5 × 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

WZI seminar Experimental setup sample PL Variable wavelength nm ( eV) nm ( 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

WZI seminar 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

WZI seminar Excitation flux dependence

WZI seminar Excitation flux dependence

WZI seminar Excitation flux dependence

WZI seminar Excitation flux dependence

WZI seminar Excitation flux dependence

WZI seminar Excitation flux dependence  = 8.7 x cm 2

WZI seminar Excitation flux dependence

WZI seminar Pulsed and continuous excitation Pulsed Continuous =520 nm 30 = nm 90 = 488 nm

WZI seminar Conclusion ~33% ~66% ~0.2% SiO 2 :Si-nc,Er

WZI seminar 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, St. Petersburg, Russia G. Franzò, D. Pacifici, F. Priolo, INFM and Dipartamento di Fisica e Astronomia, Università di Catania, Corso Italia 57, I Catania, Italy F. Iacona CNR-IMETEM, Stradale Primosole 50, I Catania, Italy Acknowledgements Financial support: NWO, ARL-ERO