Mn in ferromagnetic GaMn As T Lima 1 on behalf of the ECSLI collaboration IS453 and IS580 V Augustyns 1 U Wahl 3 J G Correia 3 A Costa 3 D da Silva ID: 790911
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Slide1
Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As
T.
Lima1 (on behalf of the EC-SLI collaboration – IS453 and IS580)V. Augustyns1, U. Wahl3, J. G. Correia3, A. Costa3, D. da Silva2, J. P. Araújo2, K. W. Edmonds5, B. L. Gallagher5, R. P. Campion5, M. J. Van Bael5, K. Temst1, Vantomme1, L. M. C. Pereira11. KU Leuven, Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium2. IFIMUP-IN, Universidade do Porto, 4169-007 Porto, Portugal3. C2TN, Instituto Superior Técnico, Universidade de Lisboa, 2686-953 Sacavém, Portugal4. School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom5. KU Leuven, Laboratory of Solid-State Physics and Magnetism, 3001 Leuven, Belgium
Tiago Lima |
KULeuven
,
Instituut
voor
Kern-
en
Stralingsfysica
| tiago.lima@fys.kuleuven.be
Slide2Outline(Ga,Mn)As: model DMSemission channeling
identification of the interstitial sitethermal stability (of interstitial and substitutional)conclusions and outlook
Slide3Curie Temperature 185 K for a Mn concentration of 10%
(Ga,Mn)As: model DMS
Wang, Mu, et al. "Achieving high curie temperature in (Ga,Mn)As." Applied Physics Letters 93.13 (2008): 132103.Dietl, Tomasz, and Hideo Ohno. "Dilute ferromagnetic semiconductors: physics and spintronic structures." Reviews of Modern Physics 86.1 (2014): 187.Tiago Lima3Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)AsGaAs
Mn
Ga
h
+
h
+
Mn
I
magnetic and electrical
compensation
by
Mn
I
Air annealing
~
180
º
C
Interstitial
Mn
Which lattice site (T
As
or
T
Ga
)?
Why/How is it formed?
How does it diffuse?
Why is the optimal annealing temperature window so narrow?
Slide4Ga
As
-
decay
electron yield
angle
e
mission
channeling
Slide5Tiago Lima5Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As
Angular dependence of emitted electrons measured with a position sensitive Si-pad detector
(Medipix detectors coming soon) Fit 2D experimental patterns with simulations for each lattice site Determine the occupied sites and respective fractionsemission channeling
Slide6Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As
6Tiago Lima
identification of the interstitial siteInterstitial Mn occupies the TAs interstitial siteexperiment best fit[deg]experimentalsubtracted ofsubstitutionalcomponentsimulatedinterstitialTGa/TAspatterns<211>
Slide7Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As
7
Two Mn concentrations: 1% and 5% diffusion → decrease in site fractioninterstitial: due to passivation at the surfacesubstitutional: due to segregation activation energy decreases with increasing Mn concentration interstitial: due to charge screeningnew insight: why/how is it formed? substitutional: direct effect of concentrationnew insight: why is the optimal annealing window so narrow?Tiago Limathermal stability (of interstitial and substitutional)substitutional
interstitial
Slide8Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As8
how does it diffuse? Tiago LimaTAs TGa TAs TGa TAsEnergy
thermal stability
(of interstitial and substitutional)
Slide9Lattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As9Tiago Lima
conclusions and outlook
(Ga,Mn)As – model system to study complex defect diffusion and annealingongoing: generalization to III-Mn-V family (GaAs, GaP, GaSb)This new understanding inspires new strategies to increase substitutional incorporation → higher Curie temperature New classes of dilute magnetic materials: Transition-metal doped topological insulators (Bi2Se3, Bi2Te3)Which lattice site? Tetrahedral TAs Why/How is it formed? Diffusion from surfaceHow does it diffuse? Always trapped in TAs sitesWhy narrow annealing temperature? Clustering of substitutional MninterstitialMn
Slide10Tiago LimaLattice location and thermal stability of Mn in ferromagnetic (Ga,Mn)As10
acknowledgementsThis work was supported
by:Fund for Scientific Research-FlandersPortuguese Foundation for Science and TechnologyKU Leuven BOFEuropean Union Seventh Framework(ENSAR and SPIRIT)