<i>In-situ</i> Investigations for Possible Two-Dimensional Electron Gases on BiO<sub>2</sub>-Terminated BaBiO<sub>3</sub> Thin Films
ORAL
Abstract
We analyzed the atomic configuration and the electronic structures of BaBiO3 (BBO) thin films adopting in-situ photoemission. Two-dimensional electron gases (2DEGs) was theoretically predicted by density-functional-theory on BiO2-terminated BBO surfaces. The so-called self-doping effect was suggested as the origin for 2DEG on BBO, which can be a generic mechanism to form 2DEGs on surfaces of charge-skipping oxides. However, direct visualization for surface atomic configuration using transmission electron microscopy has been restricted because BBO is too vulnerable to electron beam. In this work, we inferred depth-profile information for our BBO films using angle-dependent core-level spectra measurement, which is dramatically affected by finite escape depths of photoelectrons. We found that our BBO films were terminated by BiO2 layers, rather than BaO or other possible mixtures of BaO and BiO2. By measuring angle-resolved photoemission, we distinguished surface states and bulk states, and none of them showed any signatures from 2DEGs. Surface states were observed 4 eV below Fermi level, not near the Fermi level, which suggests that electronic structure description for BBO should accompany with sophisticated approaches.
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Presenters
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Ji Seop Oh
- Lawrence Berkeley Natl Lab
- Center for Correlated Electron Systems, Institute for Basic Science