Abstract

Ultra high intensity post ionization mass spectrometry combines many positive features of secondary ionization mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS). All of these techniques use ion beam sputtering to sample the material or structure in question, affording both depth profiling and surface analysis with excellent depth resolution. Post-ionization is one form of SNMS, using a laser to photoionize sputtered atoms and is relatively free from SIMS-type matrix effects. The main question of ultra high intensity post ionization is can most or all elements be detected with nearly equal efficiency? If so, then no standards are required for quantitative analysis. The ratio of signals would be equal to the ratio of elemental concentrations. By contrast, SIMS requires a standard for each analyte determined in each matrix present in the sample because ionization yields vary by many orders of magnitude. Ideally, ultra high intensity post-ionization(1) detects all species similarly with one set of laser conditions, including electronically excited atoms or molecules. Other forms of SNMS detect neutrals with varying efficiency (electron impact) or require different laser parameters (like resonant post-ionization) for multi element detection. This paper will address the sputtering of the sample, which determines the species to be ionized. The partitioning into atoms, molecules or ions strongly affects the uniformity of detection efficiency.

© 1996 Optical Society of America