ELECTRON AND ION EMISSION PROPERTIES OF IRIDIUM SUPERTIP FIELD EMITTERS

Supertip-type field emitters, consisting of a small protrusion (simila r to 1 nm) on a large base tip (similar to 100 nm), are novel powerful sources for both finely focused electron and ion beams. Due to the ch emical reactivity of the commonly used W, only noble gas and hydrogen ions can be obtained. We report the reproducible production of superti ps on chemically inert Ir-[1 1 0] single crystals. While the noble-gas ion emission properties are comparable to those of W supertips, long- time O-2(+) operation of similar to 0.1 nA has been found to leave the Ir supertip unchanged. A new explanation for the temperature dependen ce of the supertips ion current predicts the optimum operation conditi ons. In addition, stable electron currents have been obtained with int ensities of more than 100 nA at a 1% stability level. (C) 1998 Elsevie r Science B.V.