1. 3/22/05APS Meeting 2005 - Los Angeles1 Magneto-optical properties of excitons confined to single magnetic and non-magnetic quantum dots Supported by NSF and Centre of Excellence CELDIS (Poland) 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

2. 3/22/05APS Meeting 2005 - Los Angeles2 Motivation  Study of single magnetic (CdMnTe/Cd 0. 4 Zn 0. 6 Te) and non-magnetic (CdTe/ZnTe) quantum dots by using magneto-optical characterization +1/2 -1/2 -3/2 +1/2 +3/2 σ -σ - σ +σ + -1/2 +3/2 -3/2 EgEg VB CB Non-DMS DMS B>0B=0B>0 σ -σ - σ +σ + Emission of and give information about g*-factor, and size of a quantum dot. 

3. 3/22/05APS Meeting 2005 - Los Angeles3 Samples GaAs ZnTe [001] Molecular Beam Epitaxy: CdTe 280 o C 2D CdTe/ZnTe CdMnTe/Cd 0.4 Zn 0.6 Te GaAs Cd 0.4 Zn 0.6 Te CdMnTe QDs Te 25 o C UHV CdTe CdTe QDs 220 o C n~100-1000 dots/µm 2 CdTe QDs ZnTe New technique: (Mariette et al., App. Phy. Lett. 82, 4340 (2003)) Can’t obtain without new technique!!

4. 3/22/05APS Meeting 2005 - Los Angeles4 Solid Immersion Lens (SIL)  To look at a small area on sample surface - SIL with index of refraction n will reduce laser spot size by factor of n - Increase collection efficiency (due to increase of numerical aperture and reduce of total internal reflection) Hemispherical SIL (LAFN9 glass n=1.83) laser luminescence Resolution~400nm (S.Mansfield and G. Kino et al.,App. Phy. Lett. 57, 2615 (1990)) sample

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

6. 3/22/05APS Meeting 2005 - Los Angeles6 Non-magnetic CdTe dots: Image 2 1 3 ~400nm 1

7. 3/22/05APS Meeting 2005 - Los Angeles7 Non-magnetic CdTe dots: Dot size (B=3T) 2 (  E=0.6meV) (a B ~ 10nm)

8. 3/22/05APS Meeting 2005 - Los Angeles8 Non-magnetic CdTe dots: g*-factor Small dots Large dots ?

9. 3/22/05APS Meeting 2005 - Los Angeles9 Magnetic CdMnTe dots: Splitting 2 1

10. 3/22/05APS Meeting 2005 - Los Angeles10 Magnetic dot vs. non-magnetic dot sp-d exchange interaction -1/2 -3/2 +1/2 +3/2 σ -σ - σ +σ + +1/2 -1/2 +3/2 -3/2 EgEg VB CB Non-DMS DMS B>0 B=0B>0 σ -σ - σ +σ +

11. 3/22/05APS Meeting 2005 - Los Angeles11 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