Electron stimulated desorption of anionic fragments from films of pure and electron-irradiated thiophene

M. N. Hedhili, P. Cloutier, A. D. Bass*, T. E. Madey, L. Sanche

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    28 Scopus citations

    Abstract

    The electron stimulated desorption (ESD) of anions is used to explore the effects of electron irradiation on a thiophene film and we report measurements for electron impact on multilayer thiophene condensed on a polycrystalline platinum substrate. Below 22 eV and at low electron dose, desorbed anions include H - (the dominant signal) as well as S -, CH 2 -, SH - and SCH 2 -. Yield functions show that anions are desorbed both by dissociative electron attachment (DEA) with resonances observed at 9.5, 11, and 16 eV, and for energies >13 eV, by dipolar dissociation (DD). An increase in the S - signal from electron irradiated (beam-damaged) thiophene films and the appearance of a new DBA resonance in the S - yield function at 6 eV are linked to rupture of the thiophene ring and the formation of sulfur-terminated products within the film. The threshold energy for ring rupture is 5 eV. The desorption of new anions such as C 4H 3S - (Thiophene-H) -is also observed from electron irradiated films and these likely arise from the decomposition of large radiation product molecules synthesized in the film. The yield functions of H -, S -, SH -, (Thiophene-H) -, and (Thiophene+H) - anions from irradiated thiophene films that have been annealed to 300 K, each exhibit a single resonant feature centered around 5.1 eV, suggesting that all signals derive from DBA to the same molecular radiation product. In contrast, only H - and S - are observed to desorb from films of 2-2-bithiophene and no resonance is seen below ∼10 eV in the anion yield functions. These data suggest that electron irradiation causes formation of ring-opened oligomers, and that closed-ring or "classical" oligomers, (similar to bithiophene) if formed, contribute little to the BSD of anions.

    Original languageEnglish (US)
    Article number094704
    JournalJournal of Chemical Physics
    Volume125
    Issue number9
    DOIs
    StatePublished - 2006

    Bibliographical note

    Funding Information:
    M. N. H. and T. E. M. acknowledge support of this work by the National Science Foundation (NSF) through Grant No. CHE 0315209. The work in Sherbrooke was funded by the Canadian Institutes of Health Research, The Canadian Foundation for Innovation, Valorisation-Rechereche Québec, and l’Université de Sherbrooke. M. N. H. acknowledges financial support from l’Agence Universitaire de la Francophonie.

    ASJC Scopus subject areas

    • Physics and Astronomy(all)
    • Physical and Theoretical Chemistry

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