Robust Ti4+ states in SrTiO3 layers of La0.6Sr0.4MnO3/SrTiO3/ La0.6Sr0.4MnO3 junctions
H. Kumigashira, A. Chikamatsu, R. Hashimoto, M. Oshima, T. Ohnishi, M., Lippmaa, H. Wadati, A. Fujimori, K. Ono, M. Kawasaki, and H. Koinuma
TL;DR
This study uses photoemission spectroscopy to show that Ti ions in SrTiO3 layers of La0.6Sr0.4MnO3/SrTiO3/La0.6Sr0.4MnO3 heterojunctions remain in a stable Ti4+ state, indicating chemical stability at the interface.
Contribution
It provides direct spectroscopic evidence that Ti ions maintain their Ti4+ oxidation state at the heterojunction interface, regardless of adjacent layer composition.
Findings
Ti4+ states are preserved at the interface
No Ti3+ states detected in TiO2 layers
Chemical stability of Ti4+ in heterojunctions
Abstract
We have investigated the interfacial electronic structure of La0.6Sr0.4MnO3 (LSMO)/ SrTiO3 (STO)/ LSMO heterojunctions utilizing the elemental selectivity of photoemission spectroscopy. The Ti 2p core-level spectra clearly show Ti4+ states and do not exhibit any indication of Ti3+ states in TiO2 layers irrespective of a different kind of adjacent atomic layer with different chemical carrier concentration. This result indicates that the Ti ions in the TiO2 atomic layers preserve their tetravalent states even in the vicinity of the valence-mismatched interface between LSMO and STO, reflecting chemical stability of the Ti4+ states.
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