Delocalized Hybrid Band in 2D Molecule-Metal Network Probed by Angle-Resolved Photoemission Spectroscopy

The electronic structure of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F₄TCNQ) monolayer grown on Au(111) has been investigated by means of angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. The high-resolution core-level photoemission spectra at the F₄TCNQ/Au(111) interface show evidences for the strong charge transfer (CT) from Au to F₄TCNQ and for the Au-atom segregation from the underlying Au(111) surface, suggesting a possible origin of the spontaneous formation of the two-dimensional F₄TCNQ-Au network. The ARPES experiment reveals a low hole-injection barrier and large CT-induced band dispersion of the F₄TCNQ-Au network due to the adatom-mediated intermolecular interaction. These results indicate that strong electron acceptor molecules with metal adtoms can form high hole-mobility molecular layers by controlling the ordered structure and their CT interaction.