INVERSE VELOCITY TRENDS IN SECONDARY-ION MASS-SPECTROMETRY - A NEW METHOD FOR QUANTIFICATION

Secondary ions from the elements of As, Cu, Ni, P, and Zn, from two standard reference materials analysed with a Cameca IMS 3f SIMS instrument were found to exhibit strong exponential-like dependences on escape velocity, particularly over the higher emission energy range. These dependences were noted under O-, O2+, and Cs+ primary ion beam conditions. After accounting for their known concentrations, the inverse velocity curves (secondary ion intensities corrected for instrument transmission and sputter yield effects plotted against the inverse of the velocity) were found to merge as infinite velocity was approached. These observations agree with quantum mechanical arguments used to describe secondary ion formation, and, in addition, suggests a new method for undertaking quantitative analysis by secondary ion mass spectrometry (SIMS). Quantification would be carried out by referencing infinite velocity values for each element of interest to that obtained from an element for which the concentration is already known.