Interface relaxation and electrostatic charge depletion in the oxide heterostructure LaAlO3/SrTiO3U. 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
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.
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.
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