A density functional theory study of oxygen diffusion in LaAlO₃ and SrTiO₃

Mireille Lontsi Fomena (1) , Antoine Villesuzanne (1) , Jean-Pierre Doumerc (1) , Christine Frayret (2) , Michel Pouchard (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314

Chemical bonding-scale aspects of oxygen diffusion in candidate high-k gate oxides LaAlO₃ and SrTiO₃ were investigated from first-principles, within density functional theory. Relaxed atomic positions, total energies and electron density maps were calculated along oxygen vacancy migration paths, for 2 2 2 supercells. Quite low activation energies were obtained (0.6 eV, in agreement with experiment) for both compounds. Microscopic factors involved in the diffusion process were investigated further by a topological analysis of the electron density, according to Bader's “Atoms in Molecules” theory. At the diffusion saddle point, transitory states such as O⁻ or atomic oxygen may explain the activation energy low values. Finally, we propose the use of energy density variation maps, as a way to identify parts of the density that contribute to increase (resp. decrease) the diffusion barrier. By extension, this type of tool may help to gain insight in phenomena such as phase transitions, and constitute the basis of an “electron density engineering” for materials design and optimization.

Mots clés: DFT; Atoms in molecules; High-k dielectrics; Oxide-ion diffusion; Electron density

Domaines: Matériaux

Mireille Lontsi Fomena, Antoine Villesuzanne, Jean-Pierre Doumerc, Christine Frayret, Michel Pouchard. A density functional theory study of oxygen diffusion in LaAlO₃ and SrTiO₃. Computational Materials Science, 2008, 44 (1), pp.53-60. ⟨10.1016/j.commatsci.2008.01.046⟩. ⟨hal-00380289⟩