The stability and surface termination of hexagonal LuFeO₃

The surface termination and the nominal valence states for hexagonal LuFeO₃ thin films grown on Al₂O₃(0 0 0 1) substrates were characterized by angle resolved x-ray photoemission spectroscopy. The Lu 4f, Fe 2p and O 1s core level spectra indicate that both the surface termination and the nominal valence depend on surface preparation, but the stable surface terminates in a Fe–O layer. This is consistent with the results of density functional calculations which predict that the Fe–O termination of LuFeO₃(0 0 0 1) surface is energetically favorable and stable over a broad range of temperatures and oxygen partial pressures when it is reconstructed to eliminate surface polarity. (paper)