PLASMA DESORPTION MASS-SPECTROMETRY IN STUDIES OF FORMATION AND SPUTTERING OF FULLERENES BY MEV ATOMIC IONS

An account is presented on plasma desorption mass spectrometry (PDMS) studies of different carbon-containing organic solids utilizing megael ectronvolt (MeV) atomic ions from the Uppsala EN-tandem accelerator. P ositive ions of even-numbered carbon clusters (C-n(+), n = 40 to >200) are ejected as a result of the interaction of the fast MeV ions with the target. The distribution of cluster sines suggests that stable, cl osed carbon-cage structures - fullerenes - are formed. Among the inves tigated materials that produce carbon clusters are poly(vinylidenefluo ride) and fluorinated fullerenes - C60F2m. For comparison purposes dat a from C-60 targets have been also collected and analyzed. PDMS has be en used for the in situ assessment of the damaging of C-60 films by Me V heavy ions. Results on delayed electron emission from C-60(-) sputte red by MeV ions from C-60 fullerene targets are also presented. A mode l of fullerene formation as a result of MeV ion interactions with the organic solid, including the yield dependence on primary ion charge st ate, is summarized. Both the data and the model suggest that fullerene s are formed as a result of a single primary ion impact and that they are ejected from an axially expanding infratrack plasma region. Result s on different types of coalescence reactions in synthetic C-60 fuller ene targets and in blends of pure (synthetic) C-60 With polystyrene le ading to ejection of higher mass positive fullerene ions (C-k(+), K fr om 60 to more than 200) are also reported. The coalescence reactions a re induced by the interaction of a single MeV ion with the solid. We a rgue that our data contribute to elucidating some general patterns of the fullerene formation mechanism.