Design and Implementation of a Micron-Sized Electron Column Fabricated by Focused Ion Beam Milling

TL;DR

This paper presents the design, fabrication, and testing of a micron-sized electron column with integrated lenses, achieving a coherent low-energy electron wave front with minimal divergence, using focused ion beam milling.

Contribution

It introduces a novel micron-scale electron column with precisely aligned lenses fabricated by focused ion beam, enabling low-energy coherent electron wave shaping.

Findings

Achieved a divergence angle of 4 mrad.

Successfully fabricated lenses with 1 and 50 micron apertures.

Demonstrated coherent electron wave shaping at 100 eV.

Abstract

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.