Favorable source material in liquid-metal-ion sources for focused beam applications

The variety of ion species is increased by using alloys as well as pure elements as the source material of liquid-metal-ion sources (LMIS’s) in focused-ion-beam (FIB) technology. Some experiments show that the base elements of the alloy affect the charge and energy distributions of emitted ions. Doubly charged ions, which have a narrower energy spread per charge and smaller energy tail than the singly charged ions, form a finer FIB. The intensity ratio of doubly to singly charged ions is expected to increase with selection of an alloy with higher surface tension, because this will strengthen the electric field at the ion emitting surface. LMIS characteristics in connection with source materials are discussed.