Electron and ion emission properties of iridium supertip field emitters

Supertip-type field emitters, consisting of a small protrusion (similar 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 chemical reactivity of the commonly used W, only noble gas and hydrogen ions can be obtained. We report the reproducible production of supertips 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 dependence of the supertips ion current predicts the optimum operation conditions. In addition, stable electron currents have been obtained with intensities of more than 100 nA at a 1% stability level. (C) 1998 Elsevier Science B.V.