Low-energy electron and ion projection microscopy

We have built a projection microscope by positioning an ultrasharp tip, prepared by field-ion microscopy techniques, in close proximity to a partly transparent carbon foil. The short distance between the perforated carbon film and the tip, achieved with an STM-like approach mechanism, leads to electron emission from the emitter at only 30 V. This arrangement provides a bright source for low-energy electrons or noble gas ions. With a detector at a macroscopic distance opposite the emitter side, a projection image of the holes and structures in the foil of about 30 nm diameter is generated by the low-energy electron beam. © 1989.