Direct fabrication of nanopores in a metal foil using focused ion beam with in situ measurements of the penetrating ion beam current.

A through hole with a diameter less than 100 nm was fabricated in an Ag foil using only a focused ion beam (FIB) system and in situ measurements of the penetrating ion beam. During the drilling of the foil by a FIB of Ga+ ions, the transmitted part of the beam was measured with an electrode mounted on the back face of the foil. When the beam current penetrating through the nanopore reached a certain value, irradiation was stopped and the area of the created aperture was measured with a scanning electron microscope. The resulting area was correlated with the current of the penetrating ion beam. This suggests that we can fabricate a nanopore of the desired size by controlling the ion beam via penetrating ion beam measurements. The smallest aperture thus created was circular with diameter of 30 nm. [ABSTRACT FROM AUTHOR]