Focused Ion Beam fabrication of Janus bimetallic cylinders acting as drift~tube Zernike phase plates

Modern nanotechnology techniques offer new opportunities for fabricating structures and devices at the micron and sub-micron level. Here, we use focused ion beam techniques to realize drift tube Zernike phase plates for electrons, whose operation is based on the presence of contact potentials in Janus bimetallic cylinders, in a similar manner to the electrostatic Aharonov-Bohm effect in bimetallic wires. We use electron Fraunhofer interference to demonstrate that such bimetallic pillar structures introduce phase shifts that can be tuned to desired values by varying their dimensions, in particular their heights.