Electronic band states of long-range ordered CuPc molecules assembled on Au(110)

The knowledge of the electronic structure of organic-inorganic interfaces is a fundamental step for the comprehension of the interplay between electronic structureand growth morphology. In particular, the nature of the metal substrate-moleculeinteraction as well as the electronic band formation at the interface are still openquestions [1]. In this work, we prepare ultrathin films of CuPc molecules depositedin UHV conditions on the Au(110)-1x2 substrate. Such an interface has been recentlyinvestigated by means of HR-UPS and LEED techniques [2]. An ordered5x3 reconstruction is detected at one monolayer by LEED, where the x3 symmetryis probably due to the reconstruction of the underlying gold substrate. Thefive-fold reconstruction can be related to CuPc molecules orderly assembled alongthe Au surface channels. The evolution of the valence band as a function of theCuPc coverage shows the appearance of interface electronic states at the monolayercoverage stage[3]. The comparison with pentacene adsorption on the Au(110) substratereveals a strong similarity in the interface electronic structure [4] suggestingthat the formation of interface states is characterized by delocalized _ electronsinteracting with Au d orbitals. In this work we present an angle-resolved high resolutionphotoemission study on the CuPc/Au(110) interface: we follow the energydispersion of these _-d interface states in the monolayer range where an ordered5x3 phase is observed and interface states are best-defined. We found that twointerface states disperse consistently with the new periodicities stemming from thesuperstructure.