title: Surface Termination Conversion during SrTiO3 Thin Film Growth Revealed by X-ray Photoelectron Spectroscopy.
abstract: Emerging electrical and magnetic properties of oxide interfaces are often dominated by the termination and stoichiometry of substrates and thin films, which depend critically on the growth conditions. Currently, these quantities have to be measured separately with different sophisticated techniques. This report will demonstrate that the analysis of angle dependent X-ray photoelectron intensity ratios provides a unique tool to determine both termination and stoichiometry simultaneously in a straightforward experiment. Fitting the experimental angle dependence with a simple analytical model directly yields both values. The model is calibrated through the determination of the termination of SrTiO3 single crystals after systematic pulsed laser deposition of sub-monolayer thin films of SrO. We then use the model to demonstrate that during homoepitaxial SrTiO3 growth, excess Sr cations are consumed in a self-organized surface termination conversion before cation defects are incorporated into the film. We show that this termination conversion results in insulating properties of interfaces between polar perovskites and SrTiO3 thin films. These insights about oxide thin film growth can be utilized for interface engineering of oxide heterostructures. In particular, they suggest a recipe for obtaining two-dimensional electron gases at thin film interfaces: SrTiO3 should be deposited slightly Ti-rich to conserve the TiO2-termination.
authors.affiliation: Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Baeumer
authors.affiliation: Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany.
authors.forename: Chencheng
authors.initials: C
authors.lastname: Xu
authors.affiliation: 1] Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany [2] Institut fuer Werkstoffe der Elektrotechnik II, RWTH Aachen University, D-52074 Aachen, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Gunkel
authors.affiliation: Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Raab
authors.affiliation: Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany.
authors.forename: Ronja Anika
authors.initials: RA
authors.lastname: Heinen
authors.affiliation: Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany.
authors.forename: Annemarie
authors.initials: A
authors.lastname: Koehl
authors.affiliation: Peter Gruenberg Institute and JARA-FIT, FZ Juelich, D-52425 Juelich, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Dittmann