Ion formation in alloy liquid-metal-ion sources

Abstract

Mass and energy analyses are carried out for ions emitted from liquid-metal-ion sources (LMISs) using Cu-P base, Pt-P, and Ni-B-Si alloys. A strong matrix effect of about 10−1 and 1 is observed on the intensity ratio of P++/P+ for Cu-P and Pt-P alloys, respectively. The electric field at the ion emitting surface is estimated to be 27–30 V/nm from the post-ionization model. A difference of only 10% in the field strength between these alloys is responsible for this matrix effect. The Ni-B-Si alloy LMIS, on the other hand, does not present an identical field strength for each component. The relationships of [ΔE(M++)/2≤ΔE(M+) <ΔE(M++)] for the energy width and [Ep(M+)≥Ep(M++)/2] for their most probable energy are observed in the energy analysis of mass-analyzed ions. Most M++ ions are formed in the post-ionization process on field-evaporated M+ ions.