Limitations to low-voltage focused ion beam operation

While standard high energy (30 keV) focused ion beam (FIB) systems have reached a very high level of technological perfection, instrument manufacturers are only just beginning to also explore the possible performance of these systems at lower landing energies of the order of a few keV or even below. Such low-voltage ion beams might be beneficially used in the preparation of cross-sectional transmission electron microscopy samples or as ion probes for depth profiling in secondary ion mass spectroscopy. In the following some of the challenges to low-voltage FIB instrumentation will be addressed using the specific example of a novel ion beam column concept based on immersion optics. Both, limitations arising from practical or operational considerations as well as from the growing impact of Coulomb interaction effects at low landing energy will be discussed.