Isotopic ratio measurements by time-of-flight secondary ion mass spectrometry

Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is often consider ed synonymous with SIMS in the static limit where the ion fluence on the sa mple surface is so low that damage is negligible. For this same reason, its use in measuring isotopic ratios has generally been ruled out. However, th e high-spatial-resolution Ga+ ion beams typically used in ToF-SIMS make it a potentially attractive technique for the isotopic characterization of sma ll features such as particles. We have developed a technique to measure iso topic ratios by ToF-SIMS with a spatial resolution of < 1 Am. Peak-fitting and interference-stripping algorithms have been developed and are presented in this work. The precision of the measurements is close to counting stati stical limits, and the variability in mass bias is comparable to dynamic SI MS. (C) 2001 Elsevier Science B.V.