Focused ion beam (FIB) technology is widely used for micromachining, which includes removal from and addition of material to a substrate with sub-micrometer beams. In order to maximize the rate at which micromachining is done it is necessary to use the highest feasible beam currents, which results in the ion beams being severely affected by spherical aberration. We have investigated the possibility of reducing the spherical aberration of a FIB focusing column by means of space charge, by introducing a negative space charge cloud into an einzel lens.
Jon Orloff, Jon Orloff,
"Spherical aberration correction of a focused ion beam with space charge", Proc. SPIE 3155, Charged Particle Optics III, (25 September 1997); doi: 10.1117/12.279398; https://doi.org/10.1117/12.279398