Stability Measurement of Ion Beam Current from Argon Field Ion Source

Abstract

We have been developing a next generation finely focused ion beam (FIB) system with noble gas field ion source (GFIS), which could reduce the contamination of irradiated ion species. Ion current stability of GFIS is one of the most fundamental factors for FIB applications. In this study, we report a preliminary measurement of current stability of field-ionized Ar+ ions from a tungsten emitter-tip which has a specific nanoprotrusion terminated by a trimer on the tip-apex. As a measure of long-term stability of Ar+ ion beam, current fluctuation of ∼5% for 1800 seconds was typically obtained at the beam current of 1.3 pA and the argon gas pressure of 5× 10-3 Pa. Furthermore it was found in argon-GFIS that the spike-like current fluctuation was correlated with the trimer-dimer transformation in a tungsten trimer-tip. [DOI: 10.1380/ejssnt.2011.371]