Despite the recent progress in developing various microanalytical tools of better spatial resolution and more sensitivity to chemical analyses for the study of various defects in metallic solids the Field-Ion Microscope (FIM) still remains the only instrument up to now to resolve single atoms in the surface of a metal. Fifteen years after Milller!) invented the FIM he was also the first to combine the FIM with a time-of-flight (To F) mass spectrometer – the so-called Atom-Probe Fl M – to identify the chemical nature of single atoms imaged in the FIM2). Originally the motivation to develop the To F atom probe was to use this method to obtain some more fundamental understanding of field ionization and field evaporation, the most basic physical processes in field-ion microscopy. Even after the successful combination of a FIM with a To F atom probe had been accomplished, the technique was rarely applied to metallurgical investigations since for a fairly long period only refractory metals such as tungsten, molybdenum, iridium, etc. could be imaged in the FIM. How- ever, these metals do not playa very important role in metallurgy. Only when Turner et 3 al. ) substituted the conventional phosphorescent screen of the field-ion microscope with micro-channel electron multiplier arrays, termed micro channel plates, did it become possible to image in the FIM the less refractory metals like Fe, Cu, Ni and even AI.
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