Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

Relative elemental sensitivity factors in secondary neutral mass spectrometry

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Using the first commercially available electron gas secondary neutral mass spectrometer (SNMS) the relative sensitivity factors D ofe/D ox were determined for 29 elements from a variety of standards of known composition. The results show an average standard deviation which increases with decreasing energy of the bombarding Ar +ions from 30% at 2 keV to 53% at 250 eV. Detailed analysis revealed that a standard deviation of 2% is due to the day-to-day reproducibility of the experimental system conditions, e.G., plasma and ion optics parameters. The remaining variations observed between different samples are attributed at least partly to matrix-dependent angular distributions of the sputtered neutral particles. Particularly the observed difference between angular distributions of alloy constituents, being most pronounced if elements of very low mass like Be, B, C, N, and O, are present in the sample, leads to a characteristic dependence of the relative sensitivity factors for these elements on the bombarding energy. It is concluded that the most reliable quantification is obtained with SNMS data taken at bombarding energies E0 >1 keV. With few exceptions, the average D fe /D ox values measured for E0 = 2 keV are found to agree reasonably well with theoretical predictions. © 1988, American Vacuum Society. All rights reserved.