Effects of backsputtered material on gallium liquid metal ion source behavior

Abstract

Backsputtered material is demonstrated to be a major factor in determining gallium liquid metal ion source (LMIS) lifetimes and I-V characteristics during operation in ultrahigh vacuum. The behavior of LMIS emission current is extremely sensitive to the type of material backsputtered onto the source tip, shaft, and reservoir. The assimilation of sputtered material is important in maintaining stable ion emission and is found to depend on the miscibility of the contaminant material in gallium. Materials which do not form solid phases when mixed with liquid gallium have the least effect on ion currents.