TOF-SIMS

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a highly sensitive analytical technique that provides chemical characterisation of the surfaces of materials. This is achieved by using a focused ion beam at typical energies of 10-30 keV, which impinges on the surface of the sample and as a result secondary ions (SI) are emitted from the uppermost atomic layers of the specimen.
The interaction volume generated by ions is of the order of few nanometers which is much smaller than that generated by an electron beam - typically of the order of few microns. As a result, TOF-SIMS can achieve better lateral and depth resolution compared to other common chemical analytical SEM techniques such as EDX.)

TOF-SIMS provides a characterisation of the surface of materials by means of mass spectra, depth profiles and elemental/molecular maps. Mass spectra allow the identification and quantification of elements, and molecular species present in the surface layers of the sample as well as the distinction of isotopes and species with similar nominal mass.

Depth profiling – an advantageous capability of this technique - is used to detect trace elements of dopants and other impurities at different depth ranges. Light elements such as Be, B and Li can be detected in very low concentrations of few ppm.

In addition, 3D chemical characterisation with high mass resolution and high spatial resolution imaging is also possible. TOF-SIMS is the ideal characterisation technique for those fields of science and technology where the composition of surfaces, thin films or layers plays an essential role in performance.

In particular, TOF-SIMS has proven to be a powerful analytical technique for the battery manufacturing industry. While techniques based on X-ray analysis fail to detect Li, the light element detection capability offered by TOF-SIMS makes it an ideal technique for conducting research in Li-ion based batteries.


The TESCAN solution for secondary ion mass spectrometry is based on integration of an orthogonal TOF-SIMS analyser with TESCAN FIB-SEM systems. Such combination enables in-situ FIB depth profiling with high mass resolution and high spatial resolution imaging. This superior performance provides the user with 3D chemical characterization and molecular information from solid materials.

Two solutions are available:


 

C-TOF analyzer highlights:

  • compactness
  • high sensitivity
  • light-element detection
  • distinguishing between isotopes
  • no need of additional ionization source
  • positive & negative ions detected
  • 3D chemical mapping
  • charge compensation possible with SEM

H-TOF analyzer highlights:

  • provides all features mentioned above
  • retractable design
  • longer flight path gives substantially higher mass resolution
Any of these two TOF-SIMS analysers can be integrated into the TESCAN FIB-SEM systems with the following additional advantages:
 

Ga+ primary ions (LYRA3, GAIA3)

Xe+ primary ions (FERA3, XEIA3)

  • high lateral resolution
  • low currents
  • high detection limit
  • limited ion implantation


TOF-SIMS
3D reconstruction of TOF-SIMS data shows 27Al+ signal (blue) and 69Ga+ (red)