We report measurements and modeling performed on an ion source based on ionization of a laser-cooled atomic beam. We show a high brightness and a low energy spread, suitable for use in next-generation, high-resolution focused ion beam (FIB) systems. Our measurements of total ion current as a function of ionization conditions support a model that also predicts the cross-sectional current density and spatial distribution of ions created in the source. The model predicts a peak brightness of 2×107 Am 2sr 1eV 1 and an energy spread < 0.34 eV. The model is also combined with Monte-Carlo simulations of the inter-ion Coulomb forces to show that the source can be operated at several picoamperes with a brightness above 1×107 Am 2sr 1eV 1. We estimate that when combined with a conventional ion focusing column, an ion source with these properties could focus a 1 pA beam into a spot smaller than 1 nm. A total current greater than 5 nA was measured in a lower-brightness configuration of the ion source, demonstrating the possibility of a high current mode of operation.
Citation: Japanese Journal of Applied Physics
Pub Type: Journals
focused ion beams, cold atoms, laser cooling