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Your guide to PVD technology, theory and applications

SNMS, Sputtered Neutral Mass Spectrometry

Posted by mark00 On March - 26 - 2010

This technique is similar to SIMS and is also known as ‘Sputtered Neutral Mass Spectrometry’. The neutral atoms are detected by post-ionising any atoms that are ejected from the surface. This post-ionisation can be accomplished by using lasers or electron bombardment of the atoms entering the mass analyser.

Ionization probabilities for particles sputtered from a surface can vary between 10^-5 to 10^-1. The remaining particles are neutral and thus vary between 90% and 99.9999% which is a much smaller variation in total flux. This fact leads to much better quantitative estimations using SNMS than SIMS.

In SNMS the sputtered neutrals are ionised at some distance away from the surface whilst suppressing the SIMS ions thereby decoupling the sputtering and ionisation effects. The technique therefore overcomes the SIMS matrix effects providing more accurate quantification in binary and ternary compounds or other complex matrices. The detection limits in SNMS are around 1e18 atoms/cc which is considerably superior to those for Auger but inferior to SIMS. The technique is particularly powerful analytical tool for obtaining compositional depth profiles.