Adsorption ofC60on Ta(110): Photoemission and CK-edge studies

Photoelectron and near-edge spectroscopies are used to characterize a ${\mathrm{C}}_{60}$ film on a Ta(110) surface. Like similar studies of ${\mathrm{C}}_{60}$ on a variety of metal surfaces, the valence band, C 1s core level, and photoelectron-derived work-function measurements show that ${\mathrm{C}}_{60}$ molecular states are aligned with the Fermi level and the charge is transferred from the metal to the fullerene. The photoelectron and near-edge spectra of the ${\mathrm{C}}_{60}$ peaks closest to the Fermi level show significant changes in intensity identifying those π-like states as interacting with the substrate. A careful examination of the C 1s and Ta 4f core levels suggests that some fraction of the fullerene overlayer decomposes on the clean metal surface leading to or resulting in, a thin layer of carbon between the assembled film and the metal substrate.