Demonstration of the voltage-controlled three-beam interference of high-energy coherent electron beam

A Boersch phase plate facilitates in-situ control of electron phase shift by altering the phase of electrons proportionally to the applied electrical potential. A device comprising of multiple such phase shifter elements will be able to modulate the wavefront of a coherent electron beam and control electron interference. In this work, we develop a fabrication method for multi-element electron phase shifter by utilizing state-of-the-art electron beam lithography and reactive ion etching techniques. We fabricated a device with three phase shifter elements in metal-insulator-metal structure and tested its electron transmission characteristics in a transmission electron microscope at beam energy of 200 keV. The experiment confirmed the voltage-controlled evolution of electron interference for individual phase shifter element. We demonstrate the voltage-controlled phase shifting properties of phase shifter elements and analyze the experimental results in comparison with 3-dimensional electrostatic simulation.