Evidence for strontium segregation in La0.7Sr0.3MnO3 thin films grown by pulsed laser deposition: consequences for tunnelling junctions

This work addresses the issue of the quality of La0.7Sr0.3MnO3 (LSMO) surfaces integrated in tunnelling junctions. From a detailed X-ray photoemission spectroscopy analysis it results that Sr segregates at the surface of LSMO films grown by pulsed laser deposition at high O2 pressure (350 mTorr). This fact is attributed to the presence of an outermost SrO layer, which is critical for the subsequent formation of a good LSMO/insulator interface. In particular we found that the unique properties of the junctions employing SrTiO3 as insulator, are strictly correlated to the integration of the SrO segregated layer in the SrTiO3 structure.