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Ferroelectric topology and electronic structure of BaTiO 3 (001)

Ferroelectric topology and electronic structure of BaTiO 3 (001). Jelle Dionot 1,2. Jointly supervised by Grégory Geneste 3,4 and Nick Barrett 2. 1 Université Paris- Sud 11 – École Doctorale 107 “Physique de la Région Parisienne ”

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Ferroelectric topology and electronic structure of BaTiO 3 (001)

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  1. Ferroelectric topology andelectronic structure of BaTiO3(001) Jelle Dionot1,2 Jointly supervised by Grégory Geneste3,4 and Nick Barrett2 1Université Paris-Sud 11 – ÉcoleDoctorale 107 “Physique de la RégionParisienne” 2Laboratoire d’Étude des Nanostructures et Imagerie de Surface (CEA-Saclay/DSM/IRAMIS/SPCSI) 3CEA/DAM – Île-de-France 4Laboratoire Structures, Propriétés et Modélisation des Solides (CNRS-UMR 8580 – ÉcoleCentrale Paris)

  2. Outline • Ferroelectric properties of single crystals • Physics and chemistry of surfaces • Stoichiometry • Doping • Strain • Experimental and theoretical approaches • Electron microscopy and spectroscopy • Ab initio simulation

  3. Ferroelectric polarization screening on single crystal Ba2+ Ti4+ O2- + + + + + + + + + + + + - + + + + + + - + + + + + + - + + + + - + + + - - - - - - - - - - - - - - - - + - - - + - - + - - - - - - - - - - - - - - - + - - - + - - + - - Intrinsic (e-h pairs, defects) + + + + + Extrinsic (adsorbates) Domain ordering - - - - - + + + - + + + + + + + + - - - - - - - + + + + +

  4. Experimentalapproach:Surface full-fieldimaging techniques 500 nm 50 nm 5 nm PEEM Photoemission threshold Work function LEEM Surface Potential Phase Transition Optical microscopy Domain ordering Polarized Light DIC

  5. Spectromicroscopy in real and reciprocal space (chemistry and band structure) Reciprocal-space imaging Real-space imaging Work function variations Surface charge differences in ferroelectric domains 3.5 eV 3.4 eV 3.3 eV 3.2 eV Direct surface chemistry Core level imaging

  6. Theoretical approach: simulation • Free standing slabs (~130 atoms) • Surface • Compensation of internal depolarizing fields • 2 supercell terminations • BaO • TiO2 • Density Functional Theory based on minimization of total energy of the system at 0 K

  7. Theoretical approach: simulation Out-of-plane polarization with uncompensated depolarizing field + - + + Barium Titanium Oxygen + + - - + - - - BaO termination - - - + + + - - - + + +

  8. Theoretical approach: simulation Out-of-plane polarization with uncompensated depolarizing field Barium Titanium Oxygen BaO termination

  9. Theoretical approach: simulation Out-of-plane polarization with uncompensated depolarizing field Barium Titanium Oxygen TiO2 termination

  10. Experiments & Calculations Calculations Experiments Oxygen vacancies stabilize inward out-of-plane polarization Surface band structure of doped BaTiO3 PRL 111, 127602 (2013) Strain-polarization coupling Surface relaxation and rumpling

  11. Thankyou for your attention! ISOE 2013 Jelle Dionot Pénultième année de thèse Bât 462, Pe 6 So far so good!

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