Non-destructive measurement of the charge transfer across LaMnO3/SrTiO3 interfaces

Local polarization and charge transfer at the interface between 7-unit cell-thick LaMnO3 (LMO) ultrathin films and substrates composed of Nb-doped (0.05 wt. %) and undoped SrTiO3 (STO) are examined by resonant surface x-ray diffraction. Notably, this photon-in photon-out technique allows us to simultaneously examine the valence distribution and local polarization with minimal radiation damage. Consistent with previous reports, Mn2+ is observed at the interface. Furthermore, the degree of charge transfer is nearly unchanged by the 0.05 wt. % of Nb doping. In the middle of the LMO films, the valence of Mn is 3+. Local polarization estimated from the cation/anion displacements shows that the electric field points outward in the LMO films, and polarization is suppressed in the STO substrate region.