Those who remember the efforts by Phillip Chang and colleagues to develop micro-columns may be interested to see that development continues apace in the physics department at the University of Zurich. This group chose to rely on FIB for the critical machining steps, and strove to minimize spherical aberration along the way.
Ref: F Wicki, et al., “Design and Implementation of a Micron-Sized Electron Column Fabricated by Focused Ion Beam Milling”, arXiv:1504.06962.