Time-of-flight secondary-ion mass spectrometry
Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) is a surface-sensitive technique, probing the outermost surface layers of a sample and providing information about its chemical composition. The great majority (ca. 95%) of the material analysed in a ToF-SIMS experiment originates from within the first two atomic layers of the sample, making the technique highly surface specific. It is also highly sensitive, with a detection limit for some species in the parts-per-million (ppm) to parts-per-billion (ppb) range.
Technique
During a ToF-SIMS experiment, the sample is bombarded with a focussed beam of high-energy primary ions, resulting in the fragmentation and ejection of material at the sample surface. Charged fragment species (the secondary ions) are then extracted from the surface and their masses determined from their flight time through the analyser. The masses of these ions are used to determine their chemical formulæ, and from this, the molecular composition of the sample surface.
Equipment
ION-TOF ToF-SIMS 5 (DSC/EDR)
- Bismuth manganese primary-ion source (Bi+, Bi3+, Bi3++, …).Heavier primary ions with greater charges improve the detection of larger secondary ions.
- Dual beam source (Cs+/O2+) for depth profiling, from a few nanometres to several microns.
- Extended dynamic range time of flight analyser.
- Spectroscopy at mass resolutions up to 10 000.
- Imaging at sub-micron spatial resolution.
- Imaging of sample regions with dimensions measuring several centimetres by rastering the motorised stage.
- Detection of secondary ions with masses up to 10 000 amu.
- Charge compensation (using low-energy-electron flooding, with or without argon-gas flooding) for analysing insulating samples.
- Sample dimensions up to 10 cm × 10 cm × 1 cm.
- Sample heating and cooling; sample rotation during depth profiling.
- In situ sample preparation facilities.
ION-TOF ToF-SIMS 5 (GCIS)
- Bismuth manganese primary-ion source (Bi+, Bi3+, Bi3++, …). Heavier primary ions with greater charges improve the detection of larger secondary ions.
- Gas cluster source (Ar) for depth profiling organic materials and soft matter.
- Spectroscopy at mass resolutions up to 10 000.
- Imaging at sub-micron spatial resolution.
- Imaging of sample regions with dimensions measuring several centimetres by rastering the motorised stage.
- Detection of secondary ions with masses up to 10 000 amu.
- Charge compensation (using low-energy-electron flooding, with or without argon-gas flooding) for analysing insulating samples.
- Sample dimensions up to 10 cm × 10 cm × 1 cm.
- Sample heating and cooling; sample rotation during depth profiling.
- In situ sample preparation facilities.