Journal of Electron Spectroscopy and Related Phenomena 155 (2007) 136–140 Photon stimulated ion desorption from intrinsically conducting polymer films based on polypyrrole doped with [Ni(dmit) 2 ] 2- C. Arantes a , A.M. Rocco b , M.L.M. Rocco a,∗ a Departamento de F´ ısico-Qu´ ımica, Instituto de Qu´ ımica, Universidade Federal do Rio de Janeiro, Cidade Universit´ aria, Ilha do Fund ˜ ao, 21949-900 Rio de Janeiro, RJ, Brazil b Departamento de Qu´ ımica Inorgˆ anica, Instituto de Qu´ ımica, Universidade Federal do Rio de Janeiro, Cidade Universit´ aria, Ilha do Fund ˜ ao, 21949-900 Rio de Janeiro, RJ, Brazil Available online 25 November 2006 Abstract Photon stimulated ion desorption and near-edge X-ray absorption fine structure studies have been performed on polypyrrole (PPy) films doped with [Ni(dmit) 2 ] 2- as counter ion. The experiments were taken at the Brazilian synchrotron light source (LNLS) operating in a single-bunch mode following sulphur K-shell photoexcitation and using time-of-flight mass spectrometry for ion analysis. At the sulphur 1s-edge ionic desorption of atomic and molecular fragments can be observed. Desorption ion yield curves have been determined as a function of the photon energy. The results showed that while the S + ion yield reproduces the photoabsorption spectrum, the S 2+ desorption is enhanced at higher energy excitations. These results are discussed in terms of the Auger stimulated ion desorption (ASID) mechanism, since these ions are not observed below the sulphur K-shell excitation region. Furthermore, for the other ionic species the indirect XESD (X-ray induced electron stimulated desorption) and the ASID processes seem to play an important role. © 2006 Elsevier B.V. All rights reserved. Keywords: Photon stimulated ion desorption (PSID); Conducting polymer films; Synchrotron radiation; Auger stimulated ion desorption (ASID); X-ray induced electron stimulated desorption (XESD) 1. Introduction Site-selective fragmentation achieved through photoexcita- tion at shallow and deep core levels has already proved to be an attractive topic in surface science since it can be correlated among other applications to the fabrication of new materials by nonthermal routes [1]. A number of studies have demonstrated that following the excitation or ionization of an inner-shell elec- tron and the corresponding relaxation through the Auger process, selective fragmentation is observed around the atom to which the inner-shell electron is closely associated [2–7]. The Auger process is therefore currently employed to explain ionic desorp- tion due to the formation of localized positive holes in valence orbitals, which leads to fragmentation and desorption through coulombic repulsion, the so-called Coulomb explosion mecha- nism [8]. In this context, the spectator Auger process has already proved to be an important step in selective fragmentation [1,5]. ∗ Corresponding author. Tel.: +55 21 2562 7786; fax: +55 21 2562 7265. E-mail address: luiza@iq.ufrj.br (M.L.M. Rocco). In this process, the photoexcited electron acts as a spectator of the Auger event. Transitions to highly antibonding orbitals will reinforce bond breaking (specific) and ion desorption. In addi- tion to the Auger stimulated ion desorption (ASID) mechanism, the indirect process namely XESD (X-ray induced electron stim- ulated desorption) seems to contribute efficiently to the signal in ionic desorption from condensed phase systems. In the XESD process desorption of surface species is induced by outgoing energetic Auger electrons and photoelectrons, most of which originated in the bulk, but also produced by the surrounding molecules especially for thick layer films. In this process ionic desorption occurs due to valence excitations and ionizations [9,10]. Intrinsically conducting polymers (ICP) such as polypyrrole (PPy) are very attractive materials because of their redox, optical and electrical properties. Such properties have been the basis for their use in batteries [11], electrochromic devices [12], capaci- tors [13] and sensors [14]. The synthesis and characterization of ICP have been studied extensively through many different tech- niques, since the understanding of the main processes occurring in this class of materials as well as the production of stable poly- 0368-2048/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.elspec.2006.11.010