Secondary ion mass spectrometry (SIMS)

Article By:

Winograd, Nicholas Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.611700

A surface analysis method for the chemical characterization of multicomponent solids and solid surfaces in many different fields. The powerful capabilities of secondary ion mass spectrometry are particularly needed as the composition of target materials becomes more sophisticated. The technique employs an energetic primary ion beam to remove or sputter atomic or molecular species from the sample. Those species that become ionized, either negatively or positively, during the collision can be detected using mass spectrometry. The sputtered ions constitute the secondary ion beam, leading to the name of the method. The power of this approach lies in the fact that the sputtered material can be analyzed with extraordinarily high chemical specificity. SIMS imaging and SIMS depth profiling, as explained below, are the two most powerful operational modes that distinguish it from other techniques. The SIMS technique is inherently destructive, since part of the sample is transported into the detector system. The kinetic energy of the primary ion beam is generally greater than several hundred electronvolts, and certainly greater than typical bond strengths, which are of the order of a few electronvolts. As a consequence, the material that is sputtered retains some chemical representation of the sample, but often contains fragment components. Moreover, the percent of neutral particles that is actually converted into measurable ions is often very small, sometimes less than 1 in 10,000. See also: Ion; Ion sources; Mass spectrometry; Sputtering

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