Ion microscope and microprobe studies of surfaces and interfaces

Secondary ion mass spectrometry (SIMS) in its spatially-resolved forms, the ion microscope and ion microprobe, offers elemental, isotopic, and molecular detection, wide dynamic intensity range spanning major to trace concentrations in the part per million (ppm) range or lower, high lateral spatial resolution in the micrometer to sub-micrometer range, shallow sampling depths to the nanometer range, and the possibility of "microanalytical tomography", the reconstruction of three-dimensional distributions. With this broad range of capabilities, SIMS has special advantages for the characterization of surfaces and interfaces that complement the measurement capabilities of other microanalysis/surface analysis techniques such as electron probe x-ray microanalysis (EPMA), analytical electron microscopy (AEM), Raman and infrared microscopy, scanning Auger electron microanalysis (SAM/AES), and spatially-resolved x-ray photoelectron spectroscopy (XPS). Examples of applications will highlight the special contributions of SIMS to surface/interface characterization studies.1. Surface studiesFigure 1 shows an example of characterization with extreme surface sensitivity. Changes in surface chemistry induced on a passivated silicon surface by scanning tunneling microscopy in air are revealed by time-of-flight secondary ion mass spectrometry (TOF-SIMS).