A quantitative assessment of microelectrodes

In order to improve the performance and applicability of atom probe tomography, the application of microelectrodes has been suggested and is realized in modern commercial instruments. In contrast to the original proposition by Nishikawa, in practical realization the down scaling of the microelectrode is limited to about 10 μm due to the requirements of a stable measurement. In this work, the field enhancement by electrodes of this size was measured in the FIM mode and compared to finite element calculations of the electric field. The experimental data reveal considerable scattering between individual microelectrodes and specimen tips, but on the average the predictions by the finite element calculation are confirmed. Even a microelectrode of 50 μm diameter yields a reasonable field enhancement close to a factor of two.