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The electronic valence band structures of polymerized thin films of C60 and La0.1C60 have been studied by using ultra-violet photoelectron spectroscopy. Additionally, the films have been characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The valence band of the C60 film shows major peaks at binding energies of 2.6, 7.2, 10.3, and 12.6 eV. In the case of the doped film, we observe (i) an additional peak with a binding energy of 13.7 eV, (ii) evidence for redistribution of the density of electronic states due to hybridization between the 5d orbitals of La and the C60 cage, and (iii) significantly higher density of the electronic states near the Fermi energy. The valence band spectra of the doped film are in good agreement with recent results of the density functional theory that support strong hybridization between the d-valence orbitals of La and the C60 cage.

We have conducted X-ray diffraction experiments in order to examine modifications in the crystal structure of C60 following compression under 31.1 GPa in a diamond anvil cell at room temperature. The material under ambient and 31.1 GPa is further characterized by laser Raman spectroscopy. The high pressure phase is identified as a mixture of body-centered orthorhombic (Immm), rhombohedral ( R 3 m ), and an unidentified phase.

We have investigated interface effects in C60/Cu-oxide/Cu structures. C60 thin films were grown under high vacuum by thermal evaporation and the well-known “pentagonal pinch mode” of C60, Ag(2) band was examined by Raman spectroscopy. We observe Raman-active bands centered at 1420, 1448, 1455, and 1465 cm−1 in C60/Cu-oxide/Cu samples with a thin (∼40 nm) C60 overlayer. The 1420, 1448, and 1455 cm−1 Raman bands are not observed in the spectra of pristine C60 powder, copper-oxide substrate, and C60/Cu-oxide/Cu samples with thick (∼1.3 μm) C60 overlayer. We associate these new Raman-active bands with C60/copper-oxide interface.