Structural, chemical, and electronic state on La[subscript 0.7]Sr[subscript 0.3]MnO[subscript 3] dense thin-film surfaces at high temperature - Surface segregation

Abstract

The evolution of the surface topographic and electronic structure and chemical state of the La0.7Sr0.3MnO3 (LSMO) thin films were probed using Scanning Tunneling microscopy and X-ray photoelectron spectroscopy to identify the structural nature of surface segregation of Sr on LSMO. The films had a layer-by-layer structure with a step height of 3.9 Å, close to the lattice parameter of LSMO. Up to 500oC in oxygen, the topography and the step heights remained the same, statistically within 2-4%, implying that no phase separation took place on the top layers. The low oxygen pressures, down to 10E-10 mbar at 500-580oC promoted segregation of Sr by 12-20% on the A-site. 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.