Development of ionic liquid ion source with porous emitter for surface modification

Ionic liquid (IL) ion sources with three different emitter tip materials, stainless steel, tungsten and graphite were developed and examined on ion beam characteristics with respect to its ILs wettability. It was observed that EMIM-BF4 ion beam produces mostly single cations or anions for positive or negative modes respectively, and exhibits a few cation-anion pairs attached with a cation or an anion. On the other hand, the main content of the BMIM-PF6 ion beam was the cation-anion pairs while the single ions were minor components. As a result of ion current measurements, the largest and the most stable emission current were obtained for the graphite emitter tip. The results indicate that the emitter wettability plays an important role in the current stability.