Influence of alkylphosphonic acid grafting on the electronic and magnetic properties of La2/3Sr1/3MnO3 surfaces

Self-assembled monolayers (SAMs) are highly promising materials for molecular engineering of electronic and spintronics devices thanks to their surface functionalization properties. In this direction, alkylphosphonic acids have been used to functionalize the most common ferromagnetic electrode in organic spintronics: La2/3Sr1/3MnO3 (LSMO). However, a study on the influence of SAMs grafting on LSMO electronic and magnetic properties is still missing. In this letter, we probe the influence of alkylphosphonic acids-based SAMs on the electronic and magnetic properties of the LSMO surface using different spectroscopies. We observe by X-ray photoemission and X-ray absorption that the grafting of the molecules on the LSMO surface induces a reduction of the Mn oxidation state. Ultraviolet photoelectron spectroscopy measurements also show that the LSMO work function can be modified by surface dipoles opening the door to both tune the charge and spin injection efficiencies in organic devices such as organic light-emitting diodes.

The research leading to these results was financially supported by the EU project NMP3-SL-2011-263104 HINTS and ANR agency (MELAMIN 2011-NANO-021). S.T. acknowledges the European Union FP7 CIG Marie Curie Actions under project SAMSFERE (FP7/2012–321739) and the Spanish MICINN for his JdC contract. P.S. wishes to thank the Institut Universitaire de France for a junior Fellowship. The research leading to these results was partly funded by the SFB/TRR 88 ‘3MET’ from the DFG. Experiments were performed on the “DEIMOS” beamline at SOLEIL Synchrotron, France (project No. 20100960).