Some aspects of liquid metal ion sources

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Abstract
SUMMARY: Liquid metal ion sources (LMIS), in view of their very high brightness, have opened new horizons in the field of ion beam technology and microscopy. In this paper some basic ion‐optical problems of LMIS‐based systems are discussed, and also some of the fundamental mechanisms concerning the operation of LMIS. While a type of field‐evaporation is a strong candidate for the main ion emission mechanism, a space‐charge based theoretical treatment successfully predicts the current‐voltage curves of LMIS of low liquid flow impedance. These conclusions are based on the most detailed measurements to date of the ‘peak energy deficit' of the ion energy distribution, and on the comparison with theory of the current‐voltage curves of a variety of LMIS. Finally, from data on gallium LMIS it is shown that an optimum operating current exists around 2 μA.