Issue
EPL
Volume 86, Number 2, April 2009
Article Number 27005
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/86/27005
Published online 06 May 2009
EPL, 86 (2009) 27005
DOI: 10.1209/0295-5075/86/27005

Interface relaxation and electrostatic charge depletion in the oxide heterostructure LaAlO3/SrTiO3

U. Schwingenschlögl1, 2 and C. Schuster2

1   ICCMP, Universidade de Brasília - 70904-970 Brasília, DF, Brazil
2   Institut für Physik, Universität Augsburg - 86135 Augsburg, Germany, EU


received 10 November 2008; accepted in final form 30 March 2009; published April 2009
published online 6 May 2009

Abstract
Performing an analysis within density functional theory, we develop insight into the structural and electronic properties of the oxide heterostructure LaAlO3/SrTiO3. Electrostatic surface effects are decomposed from the internal lattice distortion in order to clarify their interplay. We first study the interface relaxation by a multi-layer system without surface, and the surface effects, separately, by a substrate-film system. While elongation of the TiO6 octahedra at the interface enhances the metallicity, reduction of the film thickness has the opposite effect due to a growing charge depletion. The interplay of these two effects, as reflected by the full lattice relaxation in the substrate-film system, however, strongly depends on the film thickness. An inversion of the TiO6 distortion pattern for films thinner than four LaAlO3 layers results in an insulating state.

PACS
73.20.-r - Electron states at surfaces and interfaces.
73.20.At - Surface states, band structure, electron density of states.
73.40.Kp - III–V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions.

© EPLA 2009