Experimental results using an improved low-energy focussed ion beam column with booster principle and free-standing target

The design and experimental results achieved with an improved low-energy focussed ion beam (LEFIB) column are presented. The ion optical column is based on booster principle and electrostatic immersion lenses which are operated in the internal acceleration mode. Ion beam retarding is accomplished within the objective lens. Therefore the target is free-standing, i.e. on ground and in a field-free region, and the secondary electrons can easily be detected. The simulated diameters of the high-current gallium ion probe including the important underlying physics of Coulomb interaction have been confirmed in experiment, e.g. 780 nm at 1 keV landing energy, 1 nA beam current and a free working distance of 10 mm.