Journal
ADVANCED MATERIALS
Volume 33, Issue 4, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202004132
Keywords
charge-transfer; in situ spectroscopy; mesoscopic transport; oxide heterointerfaces; 2D electron-gases
Categories
Funding
- Deutsche Forschungsgemeinschaft (DFG) [DFG GU/1604, 315025796, SFB 917]
- U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [10122]
- CERIC-ERIC Consortium
- Juelich Joint Redox Lab (JJRL)
- U.S. DOE Office of Science User Facility [DE-AC02-05CH11231]
- JARA on the supercomputer JURECA [JIFF38]
- Projekt DEAL
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The electronic and ionic structure of oxide heterointerfaces play a crucial role in the phenomenon of charge transfer, and can simultaneously consider the rich chemical properties and relevant electronic properties of complex oxides. When oxygen is applied, an ionic rearrangement in the strontium cation sublattice depletes the interfacial electron gas, resulting in an inverse and reversible balance between cation vacancies and electrons.
The ability to tailor oxide heterointerfaces has led to novel properties in low-dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures. Quantitative understanding of the electronic and ionic roles regarding charge-transfer phenomena poses a central challenge. Here, the electronic and ionic structure is simultaneously investigated at the prototypical charge-transfer heterointerface, LaAlO3/SrTiO3. Applying in situ photoemission spectroscopy under oxygen ambient, ionic and electronic charge transfer is deconvoluted in response to the oxygen atmosphere at elevated temperatures. In this way, both the rich and variable chemistry of complex oxides and the associated electronic properties are equally embraced. The interfacial electron gas is depleted through an ionic rearrangement in the strontium cation sublattice when oxygen is applied, resulting in an inverse and reversible balance between cation vacancies and electrons, while the mobility of ionic species is found to be considerably enhanced as compared to the bulk. Triggered by these ionic phenomena, the electronic transport and magnetic signature of the heterointerface are significantly altered.
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