Metal/Phthalocyanine Hybrid Interface States on Ag(111)

Abstract

A phthalocyanine/Ag(111) interface state is observed for the first time using time- and angle-resolved two-photon photoemission. For monolayer films of metal-free (H₂Pc) and iron phthalocyanine (FePc) on Ag(111), the state exists 0.23 ± 0.03 and 0.31 ± 0.03 eV above the Fermi level, respectively. Angle-resolved spectra show the state to be highly dispersive with an effective mass of 0.50 ± 0.15 m_e for H₂Pc and 0.67 ± 0.14 m_e for FePc. Density functional theory calculations on the H₂Pc/Ag­(111) surface allow us to characterize this state as being a hybrid state resulting from the interaction between the unoccupied molecular states of the phthalocyanine ligand and the Shockley surface state present on the bare Ag(111) surface. This work, when taken together with the extensive literature on the 3,4,9,10-perylene tetracarboxylic dianhydride/Ag interface state, provides compelling evidence that the hybridization of metal surface states with molecular electronic states is a general phenomenon