Quantification of Sulfur in Copper by Secondary Ion Mass Spectrometry (SIMS)

Abstract

Secondary Ion Mass Spectrometry (SIMS) measurements were performed for oxygen-free copper-base alloys with various sulfur concentrations from 0.02 to 14.0 mass ppm, and the influence of molecular ions 16 O 2 - on the analysis of sulfur was studied. The secondary ion yield ratios of 34 S - to 32 S - were nearly the same as their isotopic abundance ratio in the analyzed sulfur concentration range. The secondary ion yield ratio of 16 O 2 to 16 O - decided by the high mass resolution analyses was 1.3 ± 0.5 x 10- 3 , which suggested that only 3% of the secondary ions of the 32m /e signal, where m is the mass number and e is the electric charge, would come from 16 O 3 - ions in the most dilute alloy case. From these facts, the interference by 16O 2 - ions can be neglected as far as oxygen-free copper concerns. The determination limit on the measurement of 32 S - ions was less than 0.02 mass ppm, and that on the measurement of 34 S - ions was 0.02 mass ppm with the normal resolution analyses.