Secondary ion mass spectrometry (SIMS) is one of the ion beam techniques. The sample is fired at with primary ions, which can be monatomic or cluster ions, with an energy of 0.2-25 keV. This produces neutral, positively and negatively charged particles.
The neutral particles, which represent over 90 % of the emitted material, are lost in the SIMS for analysis. The charged particles are separated with mass analyzers (mass filters). Most common are the quadrupole mass analyzer, the time of flight mass analyzer (TOF) and the magnetic sector field mass analyzer. The last two achieve mass resolutions that can resolve even the smallest mass differences. For example, Al+, BO+ and C2H3+ ions can be reliably separated from these, although all three have a nominal mass of 27. Today, resolution values of one tenth of the ion mass are reached or sometimes even undershot. After passing through the analyzer, the ions reach a detector or a detector group. The signal height as a measure for the particle quantity is used to evaluate the composition.