Field of the Invention
The invention is in the field of scientific instrumentation and more specifically in the field of electron generation.
Prior Art
Electron sources are used in a variety of systems. These include, for example, electron guns, electron microscopes, and electron ionization systems. A typical electron source includes a filament, such as a wire or ribbon heated by the passage of a current. These sources include disadvantages such as substantial heating of the filament. In various instances heating limits filament lifetime, causes undesirable reactions with background gasses, results in heating of surroundings and/or causes movement of the filament. All of these results may limit utility of an electron source.
“Field emission” electron sources utilize a fine tip or tips, such as a needle or series of microneedles to produce a very high electric field. As a result of the high field electrons are spontaneously emitted. Unfortunately the wide distribution in electron energies that results from this source makes it unsuitable or inconvenient for many applications. In addition, microneedles typically consist of micro-scale carbon structures having an abundance of reactive sites. The reactive sites result in operational lifetimes or stability periods that are limiting. These carbon structures have an abundance of reactive sites because they are typically poorly ordered structures.