Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) uses a pulsed primary ion beam (Bin+ Cs+, Arn+, etc.) to impact on a sample surface and induce a fragmentation cascade. The result is the desorption of neutrals, secondary ions (+/-) and electrons from the first few monolayers of the sample. The secondary ions can then be accelerated into a "flight tube" and their mass is determined by measuring the exact time at which they reach the detector (i.e. time-of-flight).

A single secondary ion mass spectrum can be used to describe the constituents of one point on a surface. Alternatively, if the incident beam is rastered across several points within a given surface area, it is possible to build a chemical image map of that surface. By using incident ions such as Cs+ and Arn+ in a dual beam approach it is also possible to sputter through the top layers of the inorganic or organic surfaces respectively while monitoring the incidence profile of elemental or molecular species (i.e. depth profiling).