SIMS physical basis

The techniques of field desorption (FD) and electrohydrodynamic ionization (EHD) differ from SIMS, LD, and FAB in their physical basis and in features seen in the spectra. For example, the diquaternary ammonium salts discussed above yield intact doubly-charged ions, and fragmentation is less extensive. Nonetheless, the three classes of ions described for molecular SIMS are generally seen in FD (50). An EHD study of a series of diquaternary ammonium salts (51) led to the conclusion that the amount of internal energy deposited in EHD is less than in SIMS and FAB. The same study also indicated that FAB (liquid matrix) deposits less energy than SIMS (solid matrix), so in this case the order of energy deposition is SIMS > FAB > EHD. 

Physical and chemical mapping using AFM and ToF-SIMS are appropriate means for studying surfaces of flame retarded materials. Various interactions may take place between ammonium polyphosphate (APP), pentaerythritol (PER) and tetraethoxy-silane (TES). Whereas the reaction between APP and PER has been described [820], no direct reaction could be found between APP and TES. Marosi et al. [821] have reported imaging ToF-SIMS of APP-PER-ME-TES intumescent flame retarded (IFR) polypropylene. The image prepared on the basis of SiOjc ions proved the existence of a silicone layer between polymer and solid APP particles covered by PER. 

---