The carbon-fibre field emitter

The applications of and the problems encountered in the use of field electron emitters as cold cathode sources for electron beam devices have been reviewed. The possibility of using an etched carbon fibre as a cold electron source in such devices has been examined. A simple scanning electron microscope using a carbon-fibre field emitter has been constructed and produced stable pictures with a resolution of approximately 0·2 μm at a system pressure of 10 −5 Pa. Unlike tungsten, the fibres will emit electrons for many thousands of hours at estimated current densities of the order of 10 5 A cm −2 . Recently emission currents as high as 1 mA at applied voltages of approximately 3·5 kV have been obtained without any sign of breakdown after running continuously for 100 h.