SINGLY - AND DOUBLY-CHARGED ION FORMATION IN LIQUID-METAL-ION SOURCES

Abstract
The process of singly- and doubly-charged ion formation in liquid-metal-ion sources is studied using Cu-P, Pt-P and Pt-P-Sb alloys. Strong matrix effects are observed on the intensity ratio of P⁺⁺ to P⁺ ions and their energy widths, ΔE. This effect is explained by an increase in electric field, F, of as little as 10 % from F = 27 to 30 V/nm, which is estimated from the post-ionization model. Experimental data on ΔE agree with the prediction that a higher F brings about less space-charge effect on the emitted ions, resulting in a narrower ΔE. The origins of energy tails observed on the M⁺ energy distribution curves are discussed.