Atomic-scale observation of a graded polar discontinuity and a localized two-dimensional electron density at an insulating oxide interface
Journal
Physical Review B - Condensed Matter and Materials Physics
Journal Volume
87
Journal Issue
7
Date Issued
2013
Author(s)
Chang C.-P.
Lin J.G.
Jeng H.T.
Cheng S.-L.
Pong W.F.
Shao Y.C.
Chin Y.Y.
Lin H.-J.
Chen C.W.
Yang J.-R.
Chen C.H.
Abstract
Using atomically resolved electron energy-loss spectroscopy, the atomic-plane-by-atomic-plane, unit-cell-by-unit-cell stoichiometry, and charge characteristics of the oxide interface (Nd0.35Sr0.65) MnO3/SrTiO3, with a primitive polar discontinuity of (Nd0.35Sr0.65O)0.35+-(TiO2)0, were thoroughly investigated. (Nd0.35Sr0.65)MnO3 is a strongly correlated insulator and the interface was characterized to be insulating. The cell-specific stoichiometric evaluation unveiled an extensive interdiffusion across the interface. The plane-specific charge characterization revealed that the interdiffusion grades the primitive polar discontinuity. Despite the graded polar discontinuity, a charge transfer inversely into (Nd0.35Sr0.65)MnO3 was firmly resolved with a length scale of ∼2 nm and a charge density on the order of ∼1013/cm2 and is effectively mediated by an asymmetric Ti interdiffusion. The intricate electronic correlations of the interfacial (Nd0.35Sr 0.65)MnO3 unit cells and the interdiffusion-induced chemical disorder tend to render the charges localized, resulting in a localized two-dimensional electron density and thus the insulating interface, in distinct contrast to the conventional understanding of a vanishing charge density for an insulating interface and the metallic two-dimensional electron gas found at other classical polar-discontinuous interface systems. A potential strain manipulation on the electronic localization of the electron density was also proposed. © 2013 American Physical Society.
SDGs
Type
journal article