Combination of imaging mass spectrometry and electron microscopy for quasi nondestructive surface analysis

We report on a combination of imaging mass spectrometry (MS) and scanning electron microscopy (SEM) developed in a custom designed time-of-flight (TOF) MS instrument with laser post-ionization of sputtered atoms. Elemental (by MS) and topographical (by SEM) mapping of surfaces of heavily contaminated Si collectors from the NASA Genesis sample return mission enabled obtaining much more accurate and detailed depth distribution of the Solar Wind Mg and Ca implanted in these collectors. This is because the cleanest areas were identified by the SEM/MS mapping, and high resolution sputter depth profiling at these locations revealed near-surface (0-15 nm) depth distribution of Mg and Ca, that were used for more accurate fluence calculations of these Solar Wind species. MS imaging was virtually nondestructive at primary ion fluence 1012 cm-2, causing no effect on accuracy and precision of quantitative depth profiling that followed the imaging. We also demonstrate importance of such an approach by directly comparing high resolution depth profiles measured on clean areas versus arbitrarily selected areas.