Au(1 1 0) induced reconstruction by p conjugated molecules adsorption investigated by photoemission spectroscopy and low energy electron diffraction Fabrizio Evangelista a, * , Alessandro Ruocco a , David Pasca b , Chiara Baldacchini b , Maria Grazia Betti b , Valdis Corradini c,d , Carlo Mariani b,d a INFM, Dipartimento di Fisica, Universit a di Roma Tre, Via della Vasca Navale 84, I-00146 Rome, Italy b INFM, Dipartimento di Fisica, Universit a di Roma ‘‘La Sapienza’’, Piazzale Aldo Moro 2, I-00185 Rome, Italy c INFM, Dipartimento di Fisica, Universit a di Modena e Reggio Emilia, Via G. Campi 213/A, I-41100 Modena, Italy d INFM National Center on nanoStructures and bioSystem at Surfaces (S 3 ), Via G. Campi 213/A, I-41100 Modena, Italy Available online 4 June 2004 Abstract We present a comparative investigation of the adsorption mechanism of two organic molecules characterized by p- delocalized orbitals (copper-phthalocyanine and pentacene) deposited on the Au(1 1 0)-(1 · 2) surface, studied by means of low energy electron diffraction (LEED) and high energy-resolution ultraviolet photoemission spectroscopy (HR- UPS). The molecular adsorption induces a threefold periodicity in the [0 0 1] direction and a ·5(·6) symmetry in the [1  1 0] direction for the phthalocyanine (pentacene), as deduced by the LEED patterns. High energy-resolution pho- toemission spectra show similar hybrid interface states for both systems, indicating that the molecular interaction with the metal substrate is driven mainly by p molecular orbitals (even for the phthalocyanine). Comparing the electronic spectral density excited by different photon energies we single out the different contribution of p and d symmetry to interface states. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Gold; Aromatics; Low energy electron diffraction (LEED); Photoelectron spectroscopy; Interface states 1. Introduction Organic–inorganic interfaces represent a very interesting field of research for several recent technological applications in device technologies [1]. The understanding of the driving mechanism in the electronic states formation at the interface is a fundamental step. Metal-phthalocyanines (MPc) and pentacene are two planar organic molecules characterized by an extended delocalisation of p electrons. Nonetheless they differ both for the geometry and for the electronic structure: in fact, while pentacene is a linear sequence of five p- conjugated aromatic rings, MPcs are square * Corresponding author. Tel.: +39-06-55177054; fax: +39-06- 5579303. E-mail address: evangelista@fis.uniroma3.it (F. Evangeli- sta). 0039-6028/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.susc.2004.05.025 Surface Science 566–568 (2004) 79–83 www.elsevier.com/locate/susc