A novel scanning tunneling microscope controlled field emission microlens electron source

A field emission electron source that combines scanning tunneling microscope (STM) technology with a micromachined aperture has been explored. The STM is used to position the field emission tip over a metal aperture of 0.4–2.5 μm diam. An extraction voltage ranging from 50 to 200 V applied between the tip and the aperture results in the field emission of electrons, which pass through the aperture and can be collected on the other side. The aperture is fabricated on a silicon nitride membrane using electron beam lithography and reactive ion etching. Such a source can potentially provide a very bright, high current, low voltage source of electrons. The simple aperture can be replaced by a microlens consisting of a stacked structure of two or three thin film electrodes separated by thin film insulating spacers, and a compact, high performance electron source or complete optical system can be realized. While the concept of a miniature field emission cathode is well known, incorporation of an STM into the desi...