Unexpected termination switching and polarity compensation in LaAlO 3 /SrTiO 3 heterostructures
Publication Type
Journal Article
Authors
Singh-Bhalla, G, P.B Rossen, G.K Pálsson, M Mecklenburg, T Orvis, S Das, Y.-L Tang, J.S Suresha, D Yi, A Dasgupta, D Doenning, V.G Ruiz, A.K Yadav, M Trassin, J.T Heron, C.S Fadley, R Pentcheva, J Ravichandran, Ramamoorthy Ramesh
DOI
Abstract
Polar crystals composed of charged ionic planes cannot exist in nature without acquiring surface changes to balance an ever-growing dipole. The necessary changes can manifest structurally or electronically as observed in semiconductors and ferroelectric materials through screening charges and/or domain wall formation. In the case of prototypical polar complex oxides such as the LaAlO3/SrTiO3 system the nature of screening charges for different interface terminations is not symmetric. Electron accumulation is observed near the LaAlO3/TiO2-SrTiO3 interface, while the LaAlO3/SrO-SrTiO3 stack is insulating. Here, we observe evidence for an asymmetry in the surface chemical termination for nominally stoichiometric LaAlO3 films in contact with the two different surface layers of SrTiO3 crystals, TiO2 and SrO. Using several element-specific probes, we find that the surface termination of LaAlO3 remains AlO2 irrespective of the starting termination of SrTiO3 substrate surface. We use a combination of cross-plane tunneling measurements and first-principles calculations to understand the effects of this unexpected termination on band alignments and polarity compensation of LaAlO3/SrTiO3 heterostructures. An asymmetry in LaAlO3 polarity compensation and resulting electronic properties will fundamentally limit atomic level control of oxide heterostructures. © 2018 American Physical Society.
Journal
Physical Review Materials
Volume
2
Year of Publication
2018
ISSN
24759953
Notes
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