Secondary ion mass spectrometry

Secondary-ion mass spectrometry (SIMS) is a technique used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. The mass/charge ratios of these secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface to a depth of 1 to 2 nm. Due to the large variation in ionization probabilities among elements sputtered from different materials, comparison against well-calibrated standards is necessary to achieve accurate quantitative results. SIMS is the most sensitive surface analysis technique, with elemental detection limits ranging from parts per million to parts per billion.