Proposal for emitter shape to obtain higher ion current of gas field ion source

Abstract

The emitter shape dependence of the ion current from a gas field ion source (GFIS) was examined using numerical simulations. The simulator is constructed by an electric field calculation program and the spread sheets which were developed by authors based on the gas supply model. The gas supply for Ar was examined in this article, and was compared with that for He. As a result, when using the same emitter, it demonstrated that the effective capture area of Ar gas is 6.8-8.0 times larger than that of He. For a gas temperature of 300K, the effective capture area of Ar and He were estimated to be 0.0814 and 0.0107 μm2, respectively. It was also estimated that the ion current of Ar was 2-2.3 times larger than that of He. Through an actual experiment, a similar tendency was confirmed. For Ar, the influence of the shank taper angle to the ion current was confirmed and that influence is more effective than He. The emitter of small shank angle is capable of higher ion current. Therefore, it was concluded that the ion current can be increased through optimization of the emitter configuration. © 2010 The Surface Science Society of Japan.