Field emission from metal-coated silicon tips

Microfabrication processes previously described by D. Stephani and J. Eibl (1989) were refined and used to fabricate silicon tips coated with layers of titanium, tantalum, or platinum using physical vapor deposition techniques. The emphasis was upon creating tips with a large ratio of length to diameter. The emission properties of various groupings of emitters thus formed were investigated using an accurately positioned counterelectrode. The counterelectrode was made of tungsten coated with nickel and had a well-defined tip geometry. Measurements were performed on individual groups of one, four, or nine field emitters. Fowler-Nordheim plots were made for a variety of coating materials, emitter-to-electrode spacings, and tip geometries. It is concluded that, for many applications, tip optimization should not be aimed solely at the achievement of high field strengths but that the emitting area should also be as large as possible