The electronic structure of Ag(110)c(4 × 4)C60 and Au(110)(6 × 5)C60
Abstract
C60 chemisorbs and forms ordered overlayers on both Ag(110) and Au(110)2 × 1: Ag(110)c(4 × 4)C60 and Au(110)(6 × S)C60. We use direct (UPS) and inverse photoemission spectroscopy (IPS) to examine the occupied and unoccupied electronic structure of Ag(110)c(4 × 4)C60 and IPS to examine the unoccupied electronic structure of Au(110)(6 × 5)C60. Comparing the data with multilayer spectra we observe clear and unequivocable signatures of final and initial state effects in the spectra. The final state effects take the form of screening of the ionic final state. Charge transfer from Ag(110) into first layer C60 molecules is directly observed by UPS and the interaction of first layer C60 molecules with the substrate is further evidenced by a broadening of C60 features, ascribed to a splitting of molecular orbitals. The work functions of Ag(110)c(4 × 4)C60 and Au(110)(6 × 5)C60 are found to be equal to that of bulk C60. The combination of the work function measurements and the spectroscopy give new insights into the bonding of C60 on these surfaces.