Effect of Alloy Composition in Liquid AuSi Ion Source

The enrichment of the Si concentration on the needle surface of a liquid Au60Si40 (in at%) alloy ion source proceedes up to 80 at% during ion emission, resulting in fatting at the top region of the needle. The temperature dependences of the composition in the emitted ion fluxes show that the Si ion flux concentration varys proportionally to the composition of the liquidized alloy at the reservoir according to the phase diagram of an Au-Si system. At the same time, the ratio of Au++ to Au+ increases with a decrease in the Si concentration in the liquidized alloy, which shows an increase in the electric field strength at the ion-emitting site. It is shown that the Si enrichment is due to the precipitation of Si atoms in the liquidized alloy induced by a temperature difference between the reservoir and the top of a needle.