Silicon micro-valves

New techniques have been developed at GEC Hirst Research Centre to form closely spaced silicon cathodes with a base of one micron diameter and tip radii of 300 Å. In addition to these allowing a high packing density the method of production is easier to control and the structure more reproducible over large areas. Deposition of dielectric results in an undulating surface and methods of planarisation are used before metallisation and grid definition. The excess dielectric is then removed from around the emitter leaving a completely exposed cathode surrounded by a metal grid. It can be shown that electron emission from such structures is very dependent on both the work function of the cathode material, the shape of the cathode and the radius of curvature of the emitter