| AVS 63rd International Symposium & Exhibition | |
| Novel Trends in Synchrotron and FEL-Based Analysis Focus Topic | Monday Sessions |
| Session SA+AS-MoA |
| Session: | Frontiers of Photoemission with Synchrotron and XFEL Radiation/Advances in High-resolution Imaging Techniques |
| Presenter: | Julien Rault, Synchrotron SOLEIL, France |
| Authors: | J.E. Rault, Synchrotron SOLEIL, France P. Le Fèvre, Synchrotron SOLEIL, France F. Bertran, Synchrotron SOLEIL, France J. Rebellato, Synchrotron SOLEIL, France T. Maroutian, Université Paris-Sud - CNRS, France P. Lecoeur, Université Paris-Sud - CNRS, France |
| Correspondent: | Click to Email |
The electric field control of functional properties such as spin injection is a crucial goal in oxide-based electronics. Non-volatile switching between different electron and spin transport in a tunnel junction channel can be achieved through charge accumulation or depletion at the interfaces [1, 2]. It has been recently suggested [3] that polarization-dependent spin-injection is expected at the interface between ferromagnetic SrRuO3 (SRO) and semiconducting, ferroelectric n-BaTiO3 (n-BTO), paving the way for adjustable spin-injection in full-oxide devices. This fascinating effect is due to the matching of the spin-dependent Fermi surface of SRO with n-doped BTO tube-like Fermi-surface [2, 3].
To investigate this phenomenon experimentally, we use angle-resolved photoemission spectroscopy (ARPES) to access the band structure of a buried n-BTO/SRO interface. A well-known limitation of ARPES comes from its very low probing depth (< 2 nm) due to the very low electron inelastic mean free path in the usual photon range of ARPES (1-100 eV). To overcome this limitation, we use soft x-ray photons and are able to access the interface Fermi surface below a 2-nm, upward polarized BTO thin film deposited on SRO.
Using 600 eV linearly-polarized photons, we measure the band dispersion of the interface SRO through the BTO band gap along with BTO bands for higher binding energies (see Fig. 1). The SRO-related bands were not visible at lower probing depth (photon energy ca. 250 eV) showing they actually come from the interface. Clear light-polarization dependence on the energy-momentum cuts along ΓX high-symmetry direction is shown in Figure 1. This is used to assign some parts of the Brillouin zone to specific orbitals with different spin-polarization. The in-plane Fermi surface of the interface SRO for kz = Z was also acquired and showed some clear feature fitting well the calculated band structure from Liu et al., see Figure 2.
These set of results is indicative of how soft x-ray ARPES is a technique of choice to probe the band structure of functional oxide interfaces. Combined with spin-resolved photoemission, which is available at our laboratory, it will help to better understand the spin polarization predicted in ferromagnetic/ferroelectric heterostructures.
[1] Marinova, M. et al., Nano Letters 15, 2533–2541 (2015)
[2] Liu, X., Burton, J. D., Zhuravlev, M. Y. & Tsymbal, E. Y., Physical Review Letters 114, 46601 (2015)
[3] Liu, X., Wang, Y., Burton, J. D. & Tsymbal, E. Y., Physical Review B 88, 165139 (2013)