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Direct identification of interstitial Mn in Ga 1-x Mn x As and evidence of its high thermal stability Lino Pereira 1, 2,

Direct identification of interstitial Mn in Ga 1-x Mn x As and evidence of its high thermal stability Lino Pereira 1, 2, 3 U. Wahl 2 , J. G. Correia 2, , S. Decoster 3 , J. P. Araújo 1 , A. Vantomme 3. 1 IN-IFIMUP, DFA, University of Porto, Portugal 2 ITN, Sacavém, Portugal

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Direct identification of interstitial Mn in Ga 1-x Mn x As and evidence of its high thermal stability Lino Pereira 1, 2,

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  1. Direct identification of interstitial Mn in Ga1-xMnxAs and evidence of its high thermal stability Lino Pereira1, 2, 3 U. Wahl2, J. G. Correia2,, S. Decoster3, J. P. Araújo1, A. Vantomme3 1 IN-IFIMUP, DFA, University of Porto, Portugal 2 ITN, Sacavém, Portugal 3 IKS and INPAC, K.U. Leuven, Belgium

  2. dilute magnetic semiconductors what, why and how

  3. the archetypal Ga1-xMnxAs offers all but TC above RT: substitutional vs. interstitial Mn? h+ CB MnGa Ga As MnI VB MnGa MnI h+ TCincreases with x andp TCincreases with annealing TA200 ºC H. Ohno et. al, Appl. Phys. Lett. 69, 363 (1996) H. Ohno, Science281, 951 (1998) T. Dietl, H. Ohno et al., Science 287, 1019 (2000) T. Hayashi et. al, Appl. Phys. Lett. 78, 1691 (2001) K. M. Yu et. al, Phys. Rev. B 65, 201303 (2002). K. W. Edmonds et al., Phys. Rev. Lett. 92, 037201 (2004). Ea = 0.7 eV (200 ºC)

  4. electron emission channeling principles  or  decay

  5. electron emission channeling @ ISOLDE sample holder on-line @ GHM upgraded with self-triggering readout chips (CR up 3.5 kHz) suitable for short-lived isotopes sample holder 22x22 Si pad detector

  6. lattice location of Mn in GaAs and Ga1-xMnxAs

  7. lattice location of Mn in GaAs and Ga1-xMnxAs identifying the interstitial site: TAs experimental patterns best fit [111] 56Mn on Ga-substitutional and TAsinterstitial sites [100] [110] [211]

  8. lattice location of Mn in GaAs high thermal stability of interstitial Mn Ga As MnGa MnI Arrhenius model for the thermally activated migration: f(T,Δt) = f0exp[- ν0 Δt / N exp(-Ea/ kBT)]  Ea = 1.7 – 2.3 eV » 0.7 eV (transport measurements)

  9. lattice location of Mn in Ga1-xMnxAs high thermal stability of interstitial Mn same high thermal stability as in GaAs interstitial Mn is not removed by low temperature annealing (< 200 ºC) → it segregates into Mn or MnAs clusters at higher annealing temperatures

  10. conclusions • unambiguous identification of the interstitial Mn site: TAs • evidence of its high thermal stability well above 200 ºC • activation energy of 1.7-2.3 eV (» 0.7 eV) • high thermal stability is insensitive to electronic doping • interstitial Mn in Ga1-xMnxAs is not removed by low temperature annealing • it segregates into Mn or MnAs clusters at higher annealing temperatures

  11. outlook • effect of annealing atmosphere (?) • → 56Mn emission channeling (2011) • (and EXAFS) with air/N2 annealing • which donnor defect out-diffuses at 200 ºC? • As interstitial(?) • → 73As emission channeling (2011) • prospects for • increasing TC • Mn still in the matrix: • → alternative post-growth treatment • for pure substitutional doping (?) • → RT ferromagnetism (?)

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