SIMS Instrumentation: SIMS Primary Ion Sources
Typical SIMS instruments use either a duoplasmatron or a surface ionization primary ion source (or both).
The duoplasmatron can operate with virtually any gas, but oxygen is the most common because oxygen implantation into the sample surface enhances ionization efficiency for electropositive elements. Before this oxygen enhancement effect was discovered, argon was commonly used. The oxygen plasma within the duoplasmatron source contains both O- and O2+, and either can be extracted.
The cesium surface ionization source produces Cs+ ions as Cs atoms vaporize through a porous tungsten plug.