Atomic-scale observation of a graded polar discontinuity and a localized two-dimensinal electron density at an insulating oxide interface

doi:10.1103/PhysRevB.87.075129

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Title:	Atomic-scale observation of a graded polar discontinuity and a localized two-dimensinal electron density at an insulating oxide interface
Authors:	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.;Chu, M. W.
Date:	2012-07-16
Issue Date:	2016-01-06 11:03:57 (UTC+8)
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 (Nd0.35Sr0.65)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.
Relation:	Physical Review B 87, 075129(9pages)
DOI:	10.1103/PhysRevB.87.075129
Appears in Collections:	[Graduate Institute & Department of Physics] Journal Article

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