Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 72: Low-Dimensional Systems: Poster Session

TT 72.7: Poster

Wednesday, March 18, 2015, 15:00–18:00, Poster B

Oxygen stoichiometry of LaTiO₃ thin films studied by in-situ photoemission — •Philipp Scheiderer, Alex Goeßmann, Michael Sing, and Ralph Claessen — Universität Würzburg, Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), 97074 Würzburg, Germany

As in the famous oxide heterostructure LaAlO₃/SrTiO₃ (LAO/STO) a two dimensional electron system is found at the interface between the strongly correlated Mott insulator LaTi³⁺O₃ and the band insulator STO. The stabilization of LaTi³⁺O₃ requires strong reducing growth conditions since the thermodynamically stable bulk phase is the oxygen rich La₂Ti⁴⁺₂O₇. Therefore, we have systematically studied the impact of the oxygen background atmosphere on LaTi³⁺O₃ thin film growth by PLD. Reflection high-energy diffraction intensity oscillations of the specular spot indicate a layer by layer growth mode for thin films, which merges into the formation of islands for thicker films. In-situ photoemission measurements enables us to determine the oxidation state of Ti indicating excess or lack of oxygen present in the prepared samples. Our experiments show that even for films grown in vacuum, strong oxygen excess is present probably due to oxygen out-diffusion from the STO substrate. We find that an LAO buffer layer serves as an effective barrier for this process. The spectral weight of the lower Hubbard band, being a characteristic feature for the Mott insulating phase, is found to scale inversely with the amount of excess oxygen.