Numerical simulations on capture area of gas molecules for high brightness gas field ion source

Recently, the helium ion microscope was developed by adopting a built-up W(111) emitter tip[1]. The shape of microscopic protrusion on a tip apex, i.e., single atom or trimer termination, has been actively researched. On the other hand, the shank shape of emitter remains a matter of research for obtaining an ion beam with higher brightness. To improve the brightness of gas field ion source (GFIS), in this paper, numerical simulations of field distribution around the tip apex and the shank were performed taking into account an increase of gas capture area for field ionization.