Quantitative analysis of low alloy steels by secondary ion mass spectrometry

Abstract

Positive secondary ion currents from oxygen or argon ion bombardment of iron standards have been measured. In either case, the singly-charged monatomic ion currents I/sub M/sup +// may increase when oxygen gas is introduced into the bombardment chamber, but both the amount of the increase and the oxygen pressure dependence can vary dramatically from one element to another in the same sample. When sufficient oxygen is present to saturate every I/sub M/sup +//, these currents can be corrected by a simple procedure based on Andersen's approach to obtain the concentrations of most elements to within a factor of 2 of their actual values; deviations of the remaining elements are discussed and remedies proposed. The parameter T, needed for this correction procedure, is independent of primary ion current density and equals 6300 K for O/sub 2//sup +/ or Ar/sup +/ bombardment at 5.5 keV in sufficient oxygen gas; this value apparently increases if only higher energy secondary ions are monitored. The meaning of this parameter and the origin of the oxygen enhancement effect are discussed. (auth)