Hongguang Wang (Stuttgart / DE), Vesna Srot (Stuttgart / DE), Hans Boschker (Stuttgart / DE), Jochen Mannhart (Stuttgart / DE), Peter A. van Aken (Stuttgart / DE)
Abstract text (incl. figure legends and references)
Heterointerfaces in complex oxide materials promote emergent physical properties like colossal magnetoresistance, magneto-electric coupling, fractional quantum Hall Effect, and high-Tc superconductivity, which are not found in their bulk constituents. These properties can be attributed to the reconstruction of charge, spin, and orbital ordering at interfaces. Of particular concern is the charge distribution at interfaces, which is a crucial factor in controlling the interface transport behavior. However, the study of the charge distribution is very challenging due to its small length scale and the intricate structure and chemistry at interfaces. Furthermore, the underlying origin of the interfacial charge distribution has been rarely studied in-depth and is still poorly understood.
In this study [1], we performed atomic-scale investigations of the microstructure and electronic structure at SrTiO3 (STO)-SrMnO3 (SMO) heterointerfaces by high-angle annular dark-field, annular bright-field imaging and electron energy-loss spectroscopy (EELS) using an aberration-corrected scanning transmission electron microscope (STEM). EELS analysis confirms that the charge density attains the maximum of 0.13 ± 0.07 e–/unit cell (uc) at the first SMO monolayer (Fig. 1). Based on quantitative atomic-scale STEM analysis and first-principle calculations, we explore the origin of the interfacial charge accumulation in terms of epitaxial strain-favored oxygen vacancies, cationic interdiffusion, interfacial charge transfer, and space-charge effects.
Based on EELS studies and theoretical calculations, this work provides a comprehensive description of the charge distribution and related mechanisms at SMO/STO heterointerfaces, which is beneficial for the manipulation of the functionality via charge engineering at interfaces.
Fig. 1 Electronic charge density as a function of atomic position near the interface
References:
[1] H. Wang, V. Srot, X. Jiang, M. Yi, Y. Wang, H. Boschker, R. Merkle, R. W. Stark, J. Mannhart, and P. A. van Aken. ACS Nano 14, 12697-12707 (2020).