Secondary ion emission from polymer surfaces under Ar+, Xe+ and SF5+ ion bombardment

We investigated the characteristic molecular secondary ion emission from polymer surfaces under 10 keV Ar+, Xe+ and SF+5 bombardment. Secondary ion yields of PET, PP, PTFE, PS, PC, PMMA and PEG were determined under static SIMS conditions. Damage cross sections were measured for PS and PC. We applied a time-of-flight mass spectrometer, equipped with a pulsed EI-source allowing the application of mass separated primary ion beams. Spin coated multilayers as well as surfaces of bulk polymers have been studied. Changing from Ar+ to Xe+ and to SF+5 bombardment we found a strong increase of the yield Y (up to a factor of 1000) and a much smaller increase in the corresponding damage cross sections σ (up to a factor of 6) for characteristic molecular secondary ions. Both effects are more pronounced in the high mass range. The corresponding increases in secondary ion formation efficiencies ranges between a factor of 5 and 50, depending on the polymer species, the sample preparation and the mass range. Preliminary results for monomolecular overlayers on Ag and Si indicate a similar behaviour of their characteristic secondary ion emission.