Structural , chemical , and electronic state on La [

Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. The evolution of the surface topographic and electronic structure and chemical state of the La 0.7 Sr 0.3 MnO 3 (LSMO) thin films were probed using Scanning Tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) at elevated temperature and oxygen gas environment to identify the structural nature of surface segregation of Sr on LSMO. The as-prepared films had a layer-by-layer structure with a step height of 3.9 Å, close to the lattice parameter of LSMO. Up to 500 o C, the topography and the step heights remained the same, statistically within 2-4%, implying that no phase separation took place on the top layers of the film. The low oxygen pressures, down to 10-10 mbar, at elevated temperatures promoted segregation of Sr by 12-20% on the A-site, accompanied by a smaller increase of (La+Sr)/Mn. Our results suggests two possible structures for Sr segregation; the replacement of La by Sr on the AO-surface of the LSMO which retains a perovskite termination, or a separate AO-oxide phase nucleating on the defected lower layers.