First NanoARPES Available at SOLEIL: A Powerful Tool for Studying Advanced Materials

Transcription

1 First NanoARPES Available at SOLEIL: A Powerful Tool for Studying Advanced Materials Brief Introduction:! Nanotechnology Nano-Probe Nano-ARPES Classical ARPES and NanoARPES analysis of the electronic structure of low dimensional materials:! Graphene on SiC single crystals, both on Si- and C-face! Vacuum anealed SrTiO3

2 SrTiO3: A key materias Superconductivity 2DEG Ferroelectricity Luminescence Ueno, K. et al. Electric-field-induced superconductivity in an insulator. Nature Materials 7, , doi:1.138/ nmat2298 (28). Santander-Syro, A. F. et al. Twodimensional electron gas with universal subbands at the surface of SrTiO3. Nature 469, , doi:1.138/ nature972 (211).! Kan, D. S. et al. Blue-light emission at room temperature from Ar+irradiated SrTiO3. Nature Materials 4, , doi: 1.138/nmat1498 (25). Haeni, J. H. et al. Roomtemperature ferroelectricity in strained SrTiO3. Nature 43, , doi:1.138/ nature2773 (24).! Takagi, H. & Hwang, H. Y. An Emergent Change of Phase for Electronics. Science 327, , doi:1.1126/ science (21).!

3 SrTiO3: Surface Reconstruction 1! Jiang, Q. D. & Zegenhagen, J. c(6x2)and c(4x2)reconstruction of SrTiO3(1). Surface Science 425, , doi:1.116/s39-628(99)223-x (1999).

4 Surface Electronic Structure of Vacuum Annealed SrTiO3 ARPES Nano-ARPES Γ 11 k // (1/Å) Γ k // (1/Å) Ca segregation

5 Surface Electronic Structure of Vacuum Annealed SrTiO3: 12 C

6 Surface Electronic Structure of Vacuum Annealed SrTiO3: 12 C

7 Surface Electronic Structure of Vacuum Annealed SrTiO3: 12 K Nano-ARPES Ca impurities decorate surface defects by forming a ring of 15 μm around them. Their segregation is strongly localized, has a negligible effect in the bulk, and cannot be the reason for any longrange reconstruction.

8 Surface Electronic Structure of Vacuum Annealed SrTiO3 Valence Band by ARPES

9 7 C 1 C 12 C 7 % 12% 45% Intensity (a.u.) 45 5 Kinetic energy (ev) 45 5 Kinetic energy (ev) 45 5 Kinetic energy (ev)

10 Intensity (a.u.) 459 ev 46 ev ev Ti 4+ Ti 3+ Intensity (a.u.) PEY, 1 C Ti 4+ 85% Ti 3+ 15% Residual Intensity (a.u.) PEY 7 ºC 1 ºC 12 ºC 46 Photon Energy (ev) D 3 D Intensity (a.u.) t 2g e g t 2g L 3 L 2 e g 46 Photon Energy (ev) 47 TFY [V O ].5 7 PEY 1 Temperature (ºC) TFY 12

11 2 D 3 D.5 [V O ] 7 1 Temperature (ºC) 12 2D Oxygen Vacancies

12 a 2 7 C K 1 C K 12 C K 2 2 k y (1/Å) b.5 1 k x (1/Å) k x (1/Å) 3 1 k x (1/Å) 7 C K 7 1 C K 12 7 C K.5 3 k y (1/Å) c k x (1/Å) 7 K k x (1/Å) 1 K k x (1/Å) 12 K 7 C 7 C 7 C d xy d xz / d yz k // (1/Å) k // (1/Å) k // (1/Å)

13 7 C 1 C 12 C 2D Polar Layer Electronic structure?

14 2 Γ 1 Γ 11. d xy. k y (1/Å) M X Γ Γ 11 Γ k x (1/Å) k // (1/Å) d xz -.2 Intensity (a.u.) Γ k // (1/Å) Chang, Y. J., Bostwick, A., Kim, Y. S., Horn, K. & Rotenberg, E. Structure and correlation effects in semiconducting SrTiO3. Physical Review B 81, doi:1.113/physrevb (21).

15 . d xy -.2 Γ TiO2 Large Polaron, or Frohlich Polaron Moser, S. et al. Tunable Polaronic Conduction in Anatase TiO2. Physical Review Letters 11, (213).

16 Mahan, G. D. Many body physics. (2). One Einstein phonon mode Green Function Method 9 mev EDC fit Background

17 a 5.5 X b 5.5 X k (1/Å) 5. k (1/Å) 5. Γ c k // (1/Å) k // (1/Å) 7 C 1 C 12 C High k // (1/Å) 2.2 Low d Intensity (a.u.) EDC fit

18 7 C 1 C 12 C Intensity (a.u.) EDC fit D Polar Layer, 2D polaron

19 .5 7 K.5 1 K.5 12 K 7 C 7 C 7 C k y (1/Å) k x (1/Å) k x (1/Å) k x (1/Å) cm cm cm -2 7 C 1 Å 2D Gas of Large Polaron 13 Å

20 First NanoARPES Available at SOLEIL: A Powerful Tool for Studying Advanced Materials 1. Graphene on SiC, C-face: Bernal stacked! 2. Vacuum annealed STO: Ca ring.! 3. Vacuum annealed STO: 2D Large Polaron Gas, 2D polar layer.

21 First NanoARPES Available at SOLEIL: A Powerful Tool for Studying Advanced Materials Thank you for your attention!!! Chaoyu CHEN Antares Grounp