An improved Gallium liquid metal ion source geometry for nanotechnology

In this work we present a liquid metal ion source (LMIS) geometry we have developed specifically for evaluating the potential of focused ion beams in nano-fabrication. The ion-emitter we present and detail hereafter was designed to use gallium and developed to improve both the directivity and on-axis current density of the emitted beam. In the case of a gallium beam, experimental test results are presented concerning emission stability, current voltage characteristics and in situ high voltage (1 MV) transmission electron microscope (HVTEM) observations of the emitting apex. We have developed a LMIS with unconventional operational characteristics: the threshold voltage is 17 kV (twice the normal voltage), and the on-axis angular intensity is 80 µA/sr (compared to 20 µA/sr normally). With this source we were able to demonstrate the possibility to realise nano-fabrication experiments close or below the 10 nm scale. The required ion probe properties would have been inaccessible without dedicated source development effort.