Sample charging during static SIMS studies of polymers

The effects of charging during the bombardment of poly(ethylene terephthalate) (PET) and poly(tetrafluoroethylene) (PTFE) with primary ion and atom beams are explored, with a view to developing our understanding of charge-compensation mechanisms in static secondary ion mass spectrometry (SIMS). A simple model based on a resistor and capacitor in parallel may be used to predict the behaviour of PET during atom bombardment, but PTFE exhibits anomalous behaviour, and the behaviour of both polymers during ion bombardment is complex. Simple models are inadequate to predict and explain charging phenomena in SIMS when common charge-compensation procedures are employed. An outline is sketched for a more complex model, but a full understanding will only be possible when we are able to develop an accurate description of the surface electrostatic phenomena which occur during ion and atom bombardment of polymers.