In a TOF-SIMS experiment the primary ion beam is pulsed to get good mass resolution.
Consequently the current density and also the resulting erosion speed is very low (< 0.1 nm/min).
Therefore, depth profiling with a TOF-SIMS instrument is done in the so-called dual beam mode. While the first beam is sputtering a crater, the second beam is progressively analysing the crater bottom.
The key advantage of the dual beam mode is the possibility to adjust the analysis and the sputter parameter independently, e. g. the combination of a low energy sputter beam of O2 or Cs to increase the yield of positively and negatively charged secondary ions, with a high-energy, well-focussed beam of the cluster LMIG.
A further advantage is the possibility to combine both analysis and sputter phase within one analysis cycle.
The TOF.SIMS 5 can be operated at a repetition rate of up to 50 kHz in this interlaced mode which guarantees the highest possible data rates and optimum sample structure sampling.
The DSC-S is a high current ion optical column to which two ion sources, one electron impact ion source and one thermal ionization Cesium ion source may be fitted.
This column is optimised for ultra-low energy sputtering in the dual beam depth profiling mode.
Depth profile of a buried multilayer structure. Due to the high repetition rate the structure can be resolved despite of the high sputter rate (100 nm/min).