Soft X-ray photoemission spectroscopy study on the interaction between CuFPc molecules and Si111)7  7 surface L. Lozzi * , S. Santucci INFM and Department of Physics, University of L'Aquila, Via Vetoio, I-67010 Coppito, L'Aquila, Italy Abstract High resolution soft X-ray photoemission measurements have been performed onto ultra thin ®lms of hexadeca¯uoro copper phthalocyanine deposited, at room temperature and in ultra high vacuum conditions, onto clean Si1117  7 substrate. The Si 2p spectra show the missing of the adatoms signal and the appearance of a broad feature mainly due to F±Si bonds. The Si 2p spectrum allows us to exclude the loss of copper atom from the molecule during the depo- sition. C 1s spectrum evidences the presence of Si±C interaction. These results con®rm previously published X-ray photoemission spectroscopy ¯uorine spectra, which clearly present the eects of the interaction of F atoms of the molecule with the silicon substrate and a strong modi®cation of the C 1s spectrum. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: X-ray photoelectron spectroscopy; Silicon; Chemisorption; Aromatics 1. Introduction Metal phthalocyanines MePc) are planar mol- ecules that have been extensively studied for their thermal and chemical stability, which determine a wide range of possible applications, like nonlinear optics, gas sensing and molecular electronics [1±5]. Recently the interaction between these mole- cules and dierent substrates, like Si1002  1, Si1117  7, highly oriented pyrolitic graphite HOPG), have been investigated by using several surface sensitive techniques as scanning tunneling microscopy STM) [6,7], X-ray photoemission spectroscopy XPS) [8±10], X-ray absorption spectroscopy XAS) [10]. These studies have been performed in order to investigate the chemical bonds between the molecules and the substrate and their growth mode. In particular the XPS studies have shown the modi®cation induced in the electronic structure of the molecule because of the interaction with the substrate. For example size- able variations in the Cu 2p core level spectra have been observed in submonolayer ®lms of copper phthalocyanines CuPc) onto Si1002  1 and Si1117  7 [10], while no modi®cations have been reported on the Pb 4f states after the depo- sition of PbPc on the same substrates [8]. To our knowledge Si 2p spectra have been never investigated in order to study the eects on the silicon substrate due to the interaction with the molecule. These studies are highly welcome be- cause they can give further and very important information on the chemical bonds between mol- ecule and silicon. Surface Science 482±485 2001) 669±674 www.elsevier.nl/locate/susc * Corresponding author. Tel.: +39-0862-433030 oce)/ 433097 lab); fax: +39-0862-433033. E-mail address: luca.lozzi@aquila.infn.it L. Lozzi). 0039-6028/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0039-602801)00854-8