Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) enables us to determine the atomic and molecular composition of the outermost 1 - 3 monolayers of a solid (Static SIMS). The surface under investigation is bombarded by charged particles (primary ions) with energies up to 30 keV. The resulting collisions in the sample lead to the emission of secondary ions from its outer layers. These can be subsequently analyzed with respect to their mass. Elements and molecules can be detected simultaneously. The use of time-of-flight mass analyzers allows for very low detection limits (ppb, fmole). Quantification of the data is possible by use of reference samples. Semiquantitative data can be obtained when the samples to be compared have similar compositions.

In scanning mode, the method yields chemically-resolved images with lateral resolutions down to 300 nm (100 nm in favorable cases). By maintaining the ion bombardment, the sample can be eroded layer by layer (depth profiling, sputtering, dynamic SIMS). In this way, information about elements is registered as a function of depth. Although in general the intensive ion bombardment will damage organic bonds, it is possible, under certain circumstances, to obtain molecular information (organic depth profiling). When imaging and depth profiling are combined the 3-dimensional build-up of a sample can be made visible (3D-micro area analysis).

The restrictions to samples are relatively minor. Usually, samples can be analyzed "as-received". The material needs to be stable enough in a vacuum environment. Besides solids, also powders and liquids can be analyzed.

Synonyms / Related Techniques

  • Time-of-Flight Secondary Ion Mass Spectrometry
  • Secondary Ion Mass Spectrometry (SIMS)