High-brightness Cs focused ion beam from a cold-atomic-beam ion source
Adam V. Steele, Andrew Schwarzkopf, Jabez J. McClelland, Brenton Knuffman
We present measurements of focal spot size and brightness in a focused ion beam system utilizing a laser-cooled atomic beam source of Cs ions. Spot sizes as small as (2.1 ± 0.2) nm (one standard deviation) and brightness values as high as (1.3 ± 0.1) x 107 A m-2 sr-1 eV-1 are observed with a 10 keV, 1.0 pA beam. The measured brightness is over 13 times higher than the highest brightness observed in a Ga liquid metal ion source. The behavior of brightness as a function of beam current and probe angle, and the dependence of effective source temperature on ionization energy are examined, and the performance is seen to be consistent with earlier predictions. The demonstration of this source with very high brightness producing a heavy ionic species such as Cs+ promises to allow significant improvements in resolution and throughput for such applications as next-generation circuit edit and nanoscale secondary ion mass spectrometry.