Surface-interface coupling in an oxide heterostructure: Impact of adsorbates on LaAlO 3 /SrTiO 3

Result date: 01/01/2015
Author: P. Scheiderer,
Institute: Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, Germany
Publication: Phys. Rev. B,
Instrument: EA 125
The microscopic origin of the two-dimensional electron system (2DES) at the LaAlO 3 /SrTiO 3 heterointerface remains a topic of debate. Among others, mechanisms involving surface defects acting as electron donors for the 2DES have been proposed recently. Since samples are usually investigated after exposure to air, adsorbates are a plausible candidate for such surface defects. We therefore used in situ photoelectron spectroscopy and in situ resistivity measurements to study the impact of adsorbates on the 2DES. The adsorbate coverage caused by storage in air is indeed found to induce additional charge carriers at the interface, compared to the adsorbate-free surface. In controlled adsorption experiments with water and hydrogen we identify adsorbed atomic hydrogen to induce additional charge carriers at the interface, differing from molecular water adsorption reported for samples exposed to macroscopically large volumes of water in air.