Achieving high mass resolution with the NanoSIMS 50 while preserving signal transmission from submicron probe impact areas

Abstract

Elemental and isotopic local analysis using secondary ion emission induced by the impact of a submicron ion probe (SIMS) requires: (i) efficient collection of ejected ions (sensitivity) (ii) high mass resolving power (MRP) to discard interfering species (selectivity). Matching the extracted secondary beam with the acceptance of the spectrometer is then an essential issue. The NanoSIMS 50 fits those requirements fairly well. Nonetheless, a thoughtful study of its mass spectrometer has led to higher performance and suggested further improvements.12C2D and 12C2H2 with similar peak amplitudes were separated, MRP ≅ 16 800, while preserving half of the maximum signal. MRP of about 9 000, with flat top peaks and a few percent valley between 16OD and 17OH, were obtained while maintaining about 2/3 of maximum signals. Such complete separation should allow D/H ratio measurements via 16OD/16OH with much better sensitivity than that obtained with monoatomic species.