Electronic structure of La0.7Sr0.3MnO3 thin films for hybrid organic/inorganic spintronics applications

Recently, hybrid organic/inorganic interfaces have been used in prototype spin valves, with thin films of La0.7Sr0.3MnO3 as the spin-polarized charge carrier injecting electrode. We have used x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy to study the surface properties of La0.7Sr0.3MnO3 thin films prepared by the channel-spark ablation technique. In particular, preparation of the surfaces by annealing in ultra-high-vacuum surface segregation, the valence electronic structure and work function were studied in order to provide important information for charge injection behavior. It is shown that annealing in vacuum at T<500 °C removes surface contamination and stabilizes oxygen content. The work-function values change from 4.2 to 4.8 eV depending on surface treatment. A surface layer consisting of SrO and SrCO3 of a few angstrom thick was found, which can significantly influence the spin injection properties at the interfacial region.