Relationships between cluster secondary ion mass intensities generated by different cluster primary ions.
Measurements are described to evaluate the constitution of secondary ion mass spectra for both monatomic and cluster primary ions. Previous work shows that spectra for different primary ions may be accurately described as the product of three material-dependent component spectra, two being raised to increasing powers as the cluster size increases. That work was for an organic material and, here, this is extended to (SiO(2))(t)OH(-) clusters from silicon oxide sputtered by 25 keV Bi(n)(+) cluster primary ions for n = 1, 3, and 5 and 1 < or = t < or = 15. These results are described to a standard deviation of 2.4% over 6 decades of intensity by the product of a constant with a spectrum, H(SiOH)*, and a power law spectrum in t. This evaluation is extended, using published data for Si(t)(+) sputtered from Si by 9 and 18 keV Au(-) and Au(3)(-), with confirmation that the spectra are closely described by the product of a constant with a spectrum, H(Si)*, and a simple spectrum that is an exponential dependence on t, both being raised to appropriate powers. This is confirmed with further published data for 6, 9, 12, and 18 keV Al(-) and Al(2)(-) primary cluster ions. In all cases, the major effect of intensity is then related to the deposited energy of the primary ion at the surface. The constitution of SIMS spectra, for monatomic and cluster primary ion sources, is shown, in all cases, to be consistent with the product of a constant with two component spectra raised to given powers.
Seah
Martin P
MP
Quality of Life Division, National Physical Laboratory, Teddington, Middlesex, United Kingdom.
Green
Felicia M
FM
Gilmore
Ian S
IS