A pulsed source of mono- or multi-atomic primary ions (Ga+, Bin+, Au+, C60+, ...) with an energy of a few keV bombards the sample surface. The secondary ions resulting from the interaction between the primary ions and the sample are accelerated with the same kinetic energy towards the time-of-flight analyzer, which separates them according to their m/z ratio with very good mass resolution (M/ΔM > 10,000 at mass 28). The mass spectra thus obtained represent the number of secondary ions as a function of their travel time to the detector, which is proportional to the square root of the m/z ratio.
Other complementary techniques can also be used to study the surface structure of a sample (TEM, SEM) and to analyze its chemical composition (EDX, XPS).