Photoemission study of electronic structures of fullerene and metallofullerene peapods

We have investigated the electronic structures of single‐wall carbon nanotubes (SWCNTs) encapsulating C70 fullerene and metallofullerenes M@C82 (M = La, Gd, Dy), C70 peapods (C70@SWCNT) and metallofullerene peapods (M@C82@SWCNT), using photoemission spectroscopy. The photoemission spectra of C70 and M@C82 peas are obtained by subtracting the spectrum of pristine SWCNTs from those of the corresponding peapods. The electronic structure of the C70 peas is similar to that of the C70 film. For the M@C82 peapods, on the other hand, the electronic structures of the M@C82 peas are different. For the La@C82 peapods, the singly occupied molecular orbital (SOMO) for the La@C82 peas is located nearer to the Fermi level when compared with that in the La@C82 film. For the Dy@C82 peapods, the effective Dy valence is estimated to be +2.9. This result demonstrates that effective charges move back from the C82 cage to Dy following encapsulation of Dy@C82 peas in the SWCNTs because of the strong hybridization interaction between Dy 4f and C 2p electrons, taking into account the Dy valence of +3 in the Dy@C82 film. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)