We have designed, fabricated and tested a micron-sized electron column with an overall length of about 700 microns comprising two electron lenses; a micro-lens with a minimal bore of 1 micron followed by a second lens with a bore of up to 50 microns in diameter to shape a coherent low-energy electron wave front. The design criteria follow the notion of scaling down source size, lens-dimensions and kinetic electron energy for minimizing spherical aberrations to ensure a parallel coherent electron wave front. All lens apertures have been milled employing a focused ion beam and could thus be precisely aligned within a tolerance of about 300 nm from the optical axis. Experimentally, the final column shapes a quasi-planar wave front with a minimal full divergence angle of 4 mrad and electron energies as low as 100 eV.
@article{arxiv.1504.06962,
title = {Design and Implementation of a Micron-Sized Electron Column Fabricated by Focused Ion Beam Milling},
author = {Flavio Wicki and Jean-Nicolas Longchamp and Conrad Escher and Hans-Werner Fink},
journal= {arXiv preprint arXiv:1504.06962},
year = {2015}
}