Focused ion beam fabrication of Janus bimetallic cylinders acting as drift tube Zernike phase plates for electron microscopy

Modern nanotechnology techniques offer new opportunities for fabricating structures and devices at the micrometer and sub-micrometer level. Here, we use focused ion beam techniques to realize micrometer-sized Janus bimetallic cylinders acting as drift tube devices, which are able to impart a controlled phase shift to an electron wave. The phase shift results from the presence of contact potentials in the cylinders, in a similar manner to the electrostatic Aharonov-Bohm effect in bimetallic wires. We use electron Fraunhofer interference to demonstrate that such bimetallic structures introduce phase shifts that can be tuned to desired values by varying the dimensions of the pillars, in particular their heights. Such devices are promising for electron beam shaping and for the realization of electrostatic Zernike phase plates (i.e., devices that are able to impart a constant phase shift between an unscattered and a scattered electron wave) in electron microscopy, in particular, cryo-electron microscopy.