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Magneto-optical properties of excitons confined to single magnetic and non-magnetic quantum dots

Magneto-optical properties of excitons confined to single magnetic and non-magnetic quantum dots. Thang B. Hoang , Sebastian Mackowski, Lyubov Titova, Howard E. Jackson, Leigh M. Smith University of Cincinnati Piotr Wojnar, Grzegorz Karczewski, Jacek Kossut

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Magneto-optical properties of excitons confined to single magnetic and non-magnetic quantum dots

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  1. Magneto-optical properties of excitons confined to single magnetic and non-magnetic quantum dots Thang B. Hoang, Sebastian Mackowski, Lyubov Titova, Howard E. Jackson, Leigh M. Smith University of Cincinnati Piotr Wojnar, Grzegorz Karczewski, Jacek Kossut Institute of Physics PAS, Warsaw, Poland Supported by NSF and Centre of Excellence CELDIS (Poland) APS Meeting 2005 - Los Angeles

  2. DMS +1/2 Non-DMS CB -1/2 -1/2 σ- σ+ σ- σ+ Eg -3/2 +3/2 -3/2 VB +3/2 B>0 B=0 B>0 Motivation • Study of single magnetic (CdMnTe/Cd0.4Zn0.6Te) and non-magnetic (CdTe/ZnTe) quantum dots by using magneto-optical characterization +1/2  give information about g*-factor, and Emission of and size of a quantum dot. APS Meeting 2005 - Los Angeles

  3. CdTeQDs Te CdTe ZnTe CdTeQDs 25oC UHV 220oC CdMnTeQDs n~100-1000dots/µm2 CdTe Cd0.4Zn0.6Te GaAs 2D 280oC Samples Molecular Beam Epitaxy: New technique: (Mariette et al., App. Phy. Lett. 82, 4340 (2003)) CdTe/ZnTe CdMnTe/Cd0.4Zn0.6Te [001] ZnTe GaAs Can’t obtain without new technique!! APS Meeting 2005 - Los Angeles

  4. sample Solid Immersion Lens (SIL) • To look at a small area on sample surface laser luminescence (S.Mansfield and G.Kino et al.,App. Phy. Lett. 57, 2615 (1990)) Hemispherical SIL (LAFN9 glass n=1.83) Resolution~400nm • SIL with index of refraction nwill reduce laser spot size by factor of n • Increase collection efficiency (due to increase of numerical aperture and reduce of total internal reflection) APS Meeting 2005 - Los Angeles

  5. 3D image y-position Emission energy x-position Imaging method sample y-position Defocused laser x-position • Single dot: • - spatial position • - emission energy

  6. Non-magnetic CdTe dots: Image 1 3 2 1 ~400nm APS Meeting 2005 - Los Angeles

  7. Non-magnetic CdTe dots: Dot size 2 (E=0.6meV) (B=3T) (aB ~ 10nm) APS Meeting 2005 - Los Angeles

  8. Non-magnetic CdTe dots: g*-factor ? Small dots Large dots APS Meeting 2005 - Los Angeles

  9. Magnetic CdMnTe dots: Splitting 2 1 APS Meeting 2005 - Los Angeles

  10. DMS Non-DMS +1/2 CB -1/2 σ- +1/2 -1/2 Eg σ- σ+ σ+ -3/2 +3/2 -3/2 VB +3/2 B=0 B>0 B>0 Magnetic dot vs. non-magnetic dot sp-d exchange interaction APS Meeting 2005 - Los Angeles

  11. Conclusions • Studied single magnetic and non-magnetic QDs grown by new technique • Non-magnetic dots: show dependence of exciton g*-factor on emission energy (g* changes from -4 to -1.9) • Magnetic quantum dots exhibit much larger energy splitting (g*=41) (due to sp-d exchange interaction) • Magnetic dots: large line-width due to the fluctuation of Mn+ ions APS Meeting 2005 - Los Angeles

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