Ion beam mixing effects in focused ion beam time-of-flight secondary ion mass spectrometry

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is one of the most precise techniques for measuring elemental composition and is suitable for light elements where other methods, such as x-ray energy dispersive spectroscopy, struggle. Coupled with the spatial resolution available in a focused ion beam (FIB), FIB ToF-SIMS is potentially very powerful for characterization of materials with wide-ranging applications from batteries to biomaterials. One important limitation of FIB ToF-SIMS measurements is ion beam interaction with the sample. We report that ion beam induced mixing in metallic bilayer thin films systematically exhibits correlation with the heat of mixing of the binary alloys. Our results suggest that maximum spatial resolution is obtained by minimizing ion beam interactions with the sample.