Bismuth adducted intact molecular ions [M + Bi]+ under low-energy bismuth cluster ion beams

The authors propose the use of a low-energy (sub-keV/atom) bismuth cluster ion beam for time-of-flight secondary ion mass spectrometry (TOF-SIMS). 2 keV Bi3+ at an incident angle of 65° generated bismuth-adducted secondary molecular ions [M + Bi]+, which are not observed under normal TOF-SIMS conditions. This low-energy Bi primary ion beam was used for the depth profiling of Irganox1010/Irganox1098 multilayered organic thin films. [M + Bi]+ gave a better dynamic range for both Irganox1010 and Irganox1098 layers. The results suggest that a 2 keV Bi3+ ion beam is more suitable for the depth profiling of organic thin films than a 54 keV Bi3++ ion beam of typical TOF-SIMS conditions.