Ionic liquid ion sources for focused ion beam applications: A review

Focused ion beam (FIB) technology has transformed materials science by enabling precise micro- and nano-scale modifications through ion beam interactions. Originally developed for semiconductor doping and device fabrication, FIBs use different ionization sources such as liquid metals (e.g., gallium), gas field ionization, and plasma sources. Recent advancements include the use of Ionic Liquid Ion Sources (ILIS), which promise enhanced capabilities for materials research and applications. Recent progress in the Ionic Liquid Ion Sources- Focused ion beam (ILIS-FIB) technology is presented in this overview paper. ILIS-FIB systems operate similarly to conventional systems but employ ionic liquids (ILs) as ion sources, ionizing IL molecules at the emitter tip with applied voltage and using standard focusing components to refine the ion beam. Challenges which are reviewed in this article, include maintaining pure ionic emission for stable operation, necessitating optimization of tip emitting properties, IL characteristics, and voltage settings. It was reviewed in this paper that, ILIS-FIB systems use room-temperature ILs with low melting points, low vapor pressures, and customizable chemical compositions to ensure pure ion emission and improve beam performance for emerging applications. Despite challenges in beam composition and commercial readiness, ILIS-FIB research focuses on developing mathematical models to predict beam stability and performance, advancing theoretical groundwork for refinement and eventual commercialization of ILIS-based FIB technologies in materials science. This overview can shed light on the understanding of ionic liquid ion sources for Focused Ion Beam applications.