SPATIALLY MULTIDIMENSIONAL SECONDARY-ION MASS-SPECTROMETRY ANALYSIS

This article gives a survey on recent technical developments in imaging secondary ion mass spectrometry (SIMS) analysis. In the first section, the three instrumental imaging principles (scanning ion microprobe, ion microscope, image dissector) are shortly described and their capabilities are compared. In the second section, data acquisition and data handling techniques are treated, with particular emphasis on 2-dimensional imaging and its natural extension to 3 spatial dimensions via image stacking. The potential of retrospective analytical evaluation of 3D image stacks is demonstrated. The third section concentrates on quantification techniques for mass spectra and ion images. The state of the art of image quantification is described and the limitations of the standard method, sensitivity factor correction, are demonstrated. In the fourth section the concept of ''imaging'' of an analytical sample is treated as a process of (imperfect) information transfer, transforming the spatially 3-dimensional elemental atomic density in the sample into an ''ion image'' stored in a computer. This view offers a natural mathematical concept of ''resolution'' and its dependence on instrumental as well as sample parameters. This concept can be naturally extended to statistically limited imaging where spatial resolution is not limited by instrumental parameters but rather by the number of atoms available for analysis.