Polyatomic primary ion bombardment of organic materials: experiences in routine analysis

摘要

In order to investigate the differences between monoatomic (Au_1) and polyatomic (Au_3) primary ion bombardment with respect to routine TOF-SIMS analysis, systematic studies were performed by taking ion spectra and images for identical sample positions with total primary ion dose densities below the static SIMS limit. Samples were mainly of organic origin but also inorganic materials were included. The data were evaluated qualitatively (peak patterns) as well as quantitatively (secondary ion yields). It could be shown that with few exceptions the overall peak patterns are very similar and secondary ion yields for Au_3 bombardment are significantly higher than those for Au_1. Differences occur, however, with respect to the order of this enhancement. Highest differences (more than a factor of 100) are observed for intact molecular ions from thick layers or substrates of low density. Additionally, selective enhancement effects could be observed for nitrogen containing species, sulphates and phosphates. A selective yield reduction was found for monolayer coverages of fatty acid residues on metal substrates.