Secondary Ion Mass Spectrometry (SIMS)

Secondary ion mass spectrometers (SIMS) analyze solid surfaces and thin films using a directed stream of positive or negative "primary" ions to produce "secondary" ions that are then directed into a mass spectrometer capable of determining the molecular makeup of a sample. The interface of the principal ion beam with the sample supplies adequate energy to ionize many elements. If the main beam consists of positively charged ions, the resulting ionization generates negative ions; principal beams of negative ions generally lead to the production of positive ions. While most atoms and molecules taken from the sample by the interaction are neutral, a portion of these are ionized. These ions are then sped up, concentrated and examined via a mass spectrometer.