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M. L. W. Thewalt , A. Yang, M. Steger, T. Sekiguchi, K. Saeedi, Dept. of Physics, Simon Fraser University, Burnaby BC

Highly Enriched 28 Si – new frontiers in semiconductor spectroscopy. Avogadro Project. M. L. W. Thewalt , A. Yang, M. Steger, T. Sekiguchi, K. Saeedi, Dept. of Physics, Simon Fraser University, Burnaby BC, Canada V5A 1S6

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M. L. W. Thewalt , A. Yang, M. Steger, T. Sekiguchi, K. Saeedi, Dept. of Physics, Simon Fraser University, Burnaby BC

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  1. Highly Enriched 28Si – new frontiers in semiconductor spectroscopy Avogadro Project M. L. W. Thewalt , A. Yang, M. Steger, T. Sekiguchi, K. Saeedi, Dept. of Physics, Simon Fraser University, Burnaby BC, Canada V5A 1S6 T. D. Ladd, E. L. Ginzton Laboratory, Stanford University, Stanford CA, USA (now HRL) K. M. Itoh, Keio University, Yokohama, Japan H. Riemann, N. V. Abrosimov, IKZ, Berlin, Germany A. V. Gusev, A. D. Bulanov, ICHPS, Nizhny Novgorod, Russia A. K. Kaliteevskii, O. N. Godisov, “Centrotech-ECP”, St Petersburg, Russia P. Becker, PTB, Braunschweig, Germany H.­J. Pohl, VITCON Projectconsult GmbH, Jena, Germany J. J. L. Morton, Oxford, UK S. A. Lyon, Princeton, USA SILICON – 2010 Nizhny Novgorod

  2. Natural Si: 92.2% 28Si + 4.7% 29Si + 3.1% 30Si I = 0 I = ½ I = 0 Why does the isotopic composition affect electronic and optical properties? the electron-phonon interaction E bare EG ~62 meV for natSi ΔE actual EG The renormalization goes as M -1/2 EG depends on M due to zero point motion recent review: Cardona and Thewalt Reviews of Modern Physics 77, 1173 (2005) T 0 R.T. Eg(0) increases by ~2 meV from 28Si to 30Si

  3. The spectroscopic challenge of highly enriched 28Si D. Karaiskaj et al., Phys. Rev. Lett. 86, 6010 (2001) [ FWHM < 0.005 cm-1 ] Boron BE P BE ( 8 cm-1 ~ 1 meV )

  4. Boron BE 200 neV !

  5. Improved shallow bound exciton linewidths – observation of the 31P ground state hyperfine splitting in the donor bound exciton transition. Phys. Rev. Lett. 97, 227401 (2006). Nuclear and electron spin readout… 31P prime Si qubitcandidate can we use this to polarize the spins? Initialization problem a

  6. Hyperpolarization using optical pumping Phys. Rev. Lett. 102, 257401 (2009) Almost zero equilibrium polarization

  7. Resolved bound exciton hyperfine spectroscopy gives the populations of all four donor hyperfine levels in a single measurement Nuclear polarization of 76% and electronic polarization of 90% are achieved simultaneously – in less than 1 second! Higher polarization should be possible with reduced linewidths New experiments: NMR on dilute 31P in 28Si using optical polarization and optical nuclear spin readout

  8. CW NMR

  9. Energy (nonlinear) A Why 845 Gauss? ge= 1.99850 g31P = 2.26320 Schematic energy diagram e, 31P  844.9G 34,043G  Max. 55.85 MHz A = 117.53 MHz Min. 61.68 MHz   Magnetic field (nonlinear)

  10. Magnetic Field Dependence

  11. transient NMR - Rabi Oscillations

  12. First pulsed NMR -Ramsey Fringe Experiment signal on (polarizing) measurement Lasers off p/2 p/2 on RF pulses off t RF freq. = Resonance freq. +/– 1 kHz  fringes of 1 kHz

  13.  RF  probe pump   Ramsey FringesTemperature (Pressure) dependence Pump 8(), Probe 10(), ; RF = 55,847,712 Hz;

  14. 31P Donor Hyperfine Constant • At T=1.3K (P=1.0Torr)  Hyperfine constant A = 117.5239359(2) MHz at T=1.3K [existing value 117.53(2)MHz] • At 4.2 K and 1 atm, A is 3.116 kHz (26.5 ppm) lower! Why?

  15. Pulsed NMR—Hahn echo method— PL signal on measurement (initialization) Lasers (Pump&Probe) off rotation for optical readout p/2 p p/2 on RF pulses off t t refocusing fRF = fNMR Signal decay with 2t  measurement of T2

  16. T2 from Hahn Echo Method Pump 6(), Probe 4(); RF=61,677,199Hz; B=845.3 G, T=1.3K (P=1.0Torr)  T2 = 250 ms   pump PL intensity probe   RF 2t (ms)

  17. Highly Enriched 28Si – new frontiers in semiconductor spectroscopy Resolved donor bound exciton hyperfine structure: - optical readout of 31P electron and nuclear spin - fast optical hyperpolarization of electron and nuclear spin - possibility of single donor readout - promising new approaches to silicon quantum computing - have begun NMR of 31P in 28Si combining optical readout and optical hyperpolarization Studies which were thought to be limited to isolated single atoms and ions in vacuum are now becoming possible in semiconductors.

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