Improvement of field induced oxygen etching method preparing a gas filed ion emitter with ideal shape at the atomic level

A field-induced oxygen etching method (O₂ etching) is a suitable method for preparing a single atom terminated field emitter tip. By modifying the etching conditions, we demonstrated that a nano-protrusion could be fabricated on a tungsten field emitter tip. The nano-protrusion brings about an enhancement of angular current intensity (dI/dΩ) for a gas field ion source (GFIS). The nano-protrusion is realized an ideal shape of GFIS emitter proposed by S. Kalbitzer, because the structure is well-defined at atomic level. In this paper, the model of progress process of O₂ etching is verified experimentally. Next, we mention that a good agreement is obtained in the geometrical sizes of nano-protrusion measured by field ion microscopy (FIM) and by transmission electron microscopy (TEM). Finally, in the viewpoint of practical use, reduction of fabrication time of nano-protrusion is achieved by an O₂ etching at the room temperature.