Acquisition of field ion microscope image using deflector during atom probe analysis

Abstract

Atom probe (AP) is an elemental analysis technique that ionizes surface atoms by a strong field formed by a sharp needle-shaped sample and identifies ions in an atom-by-atom manner by the time of flight mass spectrometer. The detection efficiency of AP has been estimated to be extremely high by the correlation to field ion microscopy (FIM) observations, which show the surface morphology change in atomic scale during the field evaporation of the surface layer. The estimation of detection efficiency has been indirectly done by the comparison of AP data and FIM observation. We evaluated the detection efficiency of AP directly from ion data and counting spot change in FIM images by repeating two measurements sequentially in this work. The experimentally obtained ratio between the detected count over disappeared spots was 10/33 ≈ 0.30, which was ca. 1/2 of the optimal value expected from the opening area ratio of the microchannel plate (∼0.60).