Polyatomic Primary Ion Beams

Gillen, G, Roberson, S. (1998) Preliminary evaluation of an SFs polyatomic primary ion beam for analysis of organic thin films by secondary ion mass spectrometry. Rapid Commun. Mass Spectrom., 12,1303-1312. 

Today, secondary ion mass spectrometry (SIMS) is frequently used for analysis of trace elements in solid materials, especially in semiconductors and in thin films [62,63]. Primary beam species useful in SIMS include Cs+, Oj, O, Ar+, and Ga+ at energies from 1-30 keV. The bombarding primary ion beam produces monatomic and polyatomic particles of sample... 

Figure 6.8 Interference problem in SIMS polyatomic ion formation by sputtering of borophosphosilicate glass using an 02+ primary ion beam. (R. C. Wilson, F. A. Stevie and C. W. Magee, Secondary Ion Mass Spectrometry (1989). Reproduced by permission of John Wiley Sons, Inc.)...

Investigations of cluster formation serve to explain the evaporation and atomization of sample material and ion formation processes. A further aim of cluster research is to find out under what conditions cluster or polyatomic ion formation can be influenced in order to avoid disturbing interferences and decrease the detection limits of elements. On the other hand, polyatomic ions have also been used as analyte ions for analysis, e.g. the application of MCs+ and MCs2+ dimeric and trimeric ions as analyte11 or of cluster primary ion beams (e.g., of bismuth and gold primary clusters)15 16 by the bombardment and sputtering of a solid surface in SIMS.17-21 Especially in SIMS, a multitude of cluster ions with high ion formation rates are observed.18 22 23... 

Secondary ions emitted from the sample surface are monoatomic and polyatomic ions, and single-charge and multicharge ions. Polyatomic ions are not necessarily representative of the chemical composition of the analyzed sample. In fact, polyatomic ions can be generated by the recombination of emitted monoatomic ions from contaminating elements or by the combination of a target component and the primary ion beam. 

Bombarding a sample with a primary beam of ions results in several secondary species being sputtered from a sample surface. These secondary species include monatomic and polyatomic ions of the sample material, neutrals of the sample material, resputtered primary ions, electrons and photons. The sputtered species of most analytical interest are the neutrals and secondary ions. There are techniques for... 

Appelhans AD, Delmore JE. Comparison of Polyatomic and atomic primary beams for secondary ion mass spectrometry of organics. Anal Chem 1989 61 1087-1093. 

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