Electrostatic interference control of a high-energy coherent electron beam using three-element Boersch phase shifters

Abstract

Static phase shifters have been intensely studied for generating two- and three-dimensional electron beam patterns. However, those are restricted to specific electron beam energies and microscope settings. Aiming at overcoming such limitations, the development of programmable phase shifters based on e.g. a Boersch phase is an active field of research. We recently demonstrated a three-element Boersch phase shifter device [Thakkar et al., J. Appl. Phys. 128, 134502 (2020)], which was fabricated by electron beam lithography and is compatible with up-scaling. However, it suffers from parasitic beam deflection and cross-talk. Here, we report a five-layer phase shifter device, which is based on a metal–insulator–metal–insulator–metal structure as originally envisioned by Boersch that reduces cross-talk. We demonstrate a three-element Boersch phase shifter that shows minimal beam deflection of voltage-controlled three-electron-beam interference patterns in a transmission electron microscope operated at 200 keV. The feasibility of using such multi-element phase shifter arrays is discussed in this article.