Growth and electronic structure of Sm on thin Al2O3/Ni3Al(111) films

The growth and electronic structure of vapor-deposited Sm on a well-ordered Al2O3/Ni3Al(111) ultrathin film under ultrahigh vacuum conditions at room temperature have been studied comprehensively using synchrotron radiation photoemission spectroscopy, X-ray photoelectron spectroscopy, work function measurements, scanning tunneling microscopy, and low-energy electron diffraction. Our results indicate that at room temperature Sm grows in a layer-by-layer fashion up to at least 1 ML, followed by three-dimensional growth. The interaction of Sm with Al2O3 thin films leads to an initial oxidation of Sm, accompanied by a parallel reduction of the Al2O3 substrate. Both the oxidation states of Sm2+ and Sm3+ are found at low coverage (<1 ML). The concentration of Sm2+ saturates below 0.4 ML, while that of Sm3+ keeps increasing until the metallic state of Sm appears at high coverages. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704676]