The adsorption of a bi-functional organic molecule like phenol on Si(100)2 x 1 has been investigated by synchrotron radiation-induced photoemission in the valence band, Si 2p, C 1s and O 1s core-level regions. Experiments have been carried out as a function of phenol exposure at room temperature. Phenol adsorbs on Si(100)2 x 1 through a dissociative mechanism at room temperature, interacting with the surface by its alcoholic functionality. The line-shape analysis of Si 2p spectra indicates the formation of Si-O and Si-H bonds, as a consequence of the cleavage of the C6H5O-H bond and the binding of the fragments (C6H5O-group and H atom) to the Si(100)2 x 1 surface dimers. The progressive quenching of the silicon surface dimer atoms and the corresponding intensity increase of the Si-OC6H5 and Si-H components have been observed as a function of phenol exposure. The presence of the phenoxide (C6H5O-) group on the silicon surface has been evidenced also by the C 1s spectrum, consisting of two components in a 1:5 intensity ratio, energy splitted by 1.5 eV, which can be assigned to carbon atom linked to oxygen (C-O group) and carbon atoms of the aromatic ring, respectively. (c) 2005 Elsevier B.V. All rights reserved.