ION-BEAM-INDUCED DESORPTION WITH POSTIONIZATION USING HIGH REPETITION FEMTOSECOND LASERS

Static SIMS has shown itself to be a powerful tool for surface analysis with high chemical specificity. Because of the destructive nature of the sputtering process, high spatial resolution analysis (sub-200-nm regime) requires very high yields of emitted ions since there is a very limited amount of material in each image pixel. Generally the sputtered neutral yield is significantly greater than the secondary ion yield. To attain the high sensitivities required it is therefore critical that the ejected neutrals be ionized efficiently with minimal fragmentation. This paper explores the application of a high repetition rate Ti:sapphire based femtosecond laser to the ionization of sputtered and gas phase species from a variety of representative materials including silver, indium, tryptophan, benzo[a]pyrene, p-nitroaniline and polystyrene. The effects of photon wavelength (800, 400, and 266 nm) and power density on ionization and molecular fragmentation have been studied.