Roger Herger

Perovskite Thin Films: Surface Structure, Interface Structure, and Film Growth Roger Herger

The unique combination of (a) highly brilliant x-rays produced in a modern third generation synchrotron source, (b) the availability of a fast, single-photon counting area pixel detector and (c) a pulsed laser deposition equipment for in-situ growth enables one to study both the structure and kinetics of the thin film growth of perovskites. The surface structure of titanium-dioxide-terminated strontium titanate (STO) was analyzed by surface x-ray diffraction (SXRD) for two different environments: One (cold) at room temperature and in ultra-high vacuum, and the other (hot) at elevated temperatures and in an oxygen background, i.e., under conditions typical for perovskite thin film growth. SXRD was used to determine the atomic structures of lanthanum strontium manganate thin films, grown monolayer-by-monolayer on STO by pulsed laser deposition. Structures were solved using the COBRA phase-retrieval method and subsequent structural refinement. These results allowed concluding on the onset of colossal magnetoresistance. In-situ kinetic studies of the thin film growth led to the proposition of a novel energetic smoothing mechanism for the growth of complex metal-oxide thin films.