Stretching the limits of static SIMS with C60 +

Pristine and Au-covered molecular films have been analyzed by ToF-SIMS (TRIFTTM), using 15 keV Ga+ (FEI) and 15 keV C60 + (Ionoptika) primary ion sources. The use of C60 + leads to an enormous yield enhancement for gold clusters, especially when the amount of gold is low (2 nmol/ cm2), i.e. a situation of relatively small nanoparticles well separated in space. It also allows us to extend significantly the traditional mass range of static SIMS. Under 15 keV C60 + ion bombardment, a series of clusters up to a mass of about 20,000 Da (Au100 : 19,700 Da) is detected. This large yield increase is attributed to the hydrocarbon matrix (low-atomic mass), because the yield increase observed for thick metallic films (Ag, Au) is much lower. The additional yield enhancement factors provided by the Au metallization procedure for organic ions (MetA-SIMS) have been measured under C60 + bombardment. They reach a factor of 2 for the molecular ion and almost an order of magnitude for Irganox fragments such as C4H9 +, C15H23O+ and C16H23O .