What is the principle of secondary ion mass spectrometry (SIMS)?

SIMS is an ion source that works as follows; 1. a focused primary ion beam bombards the sample with primary ions. 2. because of this, secondary ions are ejected from the sample. 3. secondary ions are collected and analysed in the mass spectrometer. SIMS is mainly used to analyse the composition of solid surfaces and thin films. the application to biological samples is limited since SIMS has insufficient sensitivity and spatial resolution.