Fabrication of a Boersch phase plate for phase contrast imaging in a transmission electron microscope

The Boersch phase plate for a transmission electron microscope (TEM) offers major advantages over other phase plate concepts. However, due to its miniature dimensions, it could not be constructed and implemented so far. We report the first successful fabrication of a Boersch phase plate, which was produced by a combination of electron-beam and focused ion-beam lithography on a freestanding silicon nitride membrane. The manufactured multilayer electrode structure was tested for its functionality as an electrostatic einzel lens in a TEM. First experiments show that it can be used as a phase shifting device, as proposed by Boersch, to optimize phase contrast transfer in transmission electron microscopy.