Valence band photoemission of Sm fullerides

Valence band structure of Sm-intercalated C60 thin films is researched with ultraviolet photoelectron spectroscopy and synchrotron-radiation photoemission spectroscopy. Most valence electrons of Sm transfer to C60，and the bonding nature is mainly ionic. No Fermi edge is observed for all stoichiometries. Thus the superconducting Sm fulleride has semiconducting property at room temperature. Density of states near the Fermi level is obtained for single phase of Sm2.75C60. Photoemission of the solid solution phase differs apparently from that of Sm2.75C60. SmxC60 (2.752.75C60 and Sm6C60, which indicates that another phase exists or Sm doping proceeds smoothly through the LUMO+1 band. The interfaces between different phases are unstable above 130 ℃.