Voltage-controlled three-electron-beam interference by a three-element Boersch phase shifter with top and bottom shielding electrodes

We report a three-element Boersch phase shifter for the wavefront manipulation of coherent electron beam. A device with five-layer structure is fabricated by the state-of-the-art lithography. In a recently reported simplified three-layer device, parasitic beam deflection by contacting wires was observed, which poses a critical obstacle for device upscaling. To minimize the effect, a five-layer structure including a top-contact-shielding electrode is adopted in this work. Despite the mechanical stresses caused by the additional layers, we successfully produced the five-layer device on a suspended thin silicon nitride membrane and tested its performance of the voltage-controlled phase shift of coherent electron beam. The experiment confirmed that the parasitic beam deflection was suppressed. Our work paves a way toward the realization of a multi-element Boersch phase shifter for a programmable holographic synthesis of electron waves in two- and three-dimensions.