Photon stimulated ion desorption from intrinsically conducting polymer films based on polypyrrole doped with [Ni(dmit)2]2−

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 S2+ 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.