ION-BEAM-INDUCED DESORPTION WITH POSTIONIZATION USING HIGH REPETITIONFEMTOSECOND LASERS

Static SIMS has shown itself to be a powerful tool for surface analysi s 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 ver y limited amount of material in each image pixel. Generally the sputte red neutral yield is significantly greater than the secondary ion yiel d. To attain the high sensitivities required it is therefore critical that the ejected neutrals be ionized efficiently with minimal fragment ation. This paper explores the application of a high repetition rate T i: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 polyst yrene. The effects of photon wavelength (800, 400, and 266 nm) and pow er density on ionization and molecular fragmentation have been studied .