A new type of gaseous field ion source (GFIS) was developed. The GFIS has several advantages that includes small energy spread (～1eV), a virtual source size of ～2nm and can be operated with inert gases such as neon, argon or helium among a wide range of gases. Research to overcome the problem of their relatively low angular current densities that hinders the use of such source in technological applications, was carried out in order to confine the ion current to a small area on the emitter surface. Small protrusions were formed by the field evaporation of a multiphase alloy that contains ultrafine (1-5nm in diameter) spherical precipitates [1]. Such type of metallurgical system is called precipitation-hardened alloy. Following field evaporation, the precipitate will protrude from the surface producing a brightly-imaging region in the field ion image. This is due to the precipitate having a higher evaporation field than the surrounding base material. The source material used was the equiatomic Ni-Al (B{sub}2-ordered) alloy doped with small amounts of W and C. The composition of the alloy and its heat treatment produced high number density of ultrafine brightly-imaging WC or W{sub}2C precipitates and low solubility of W and C in the matrix phase. Those have good mechanical strength to withstand the high stress associated with the application of high electric field.
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