Focused ion beam (FIB) milling in a cryogenic environment has the potential to serve as a cryotome to section frozen biological samples, or as a patterning tool for submicron features on organic materials. Although FIB milling of inorganic materials has been investigated extensively, ion-ice interactions and the effects of process parameters on milling characteristics remain largely unexplored. In this study, the effect of the incident angle during FIB milling of water ice was investigated. In particular, the sputtering yield and surface morphology that result from sputtering were examined. The experiments involved ion bombardment by 30 keV Ga+ on a thin film of water ice with temperature maintained at 97 K. The results show that the sputtering rate, determined by a volume loss method, increased with increasing incident angle. The maximum sputtering rate was achieved at an incident angle of approximately 70°, and dramatically decreased from 70° to 90°. Depending on the angle of incidence, different surface morphologies developed during ion bombardment and were confirmed by SEM imaging and texture analysis. At near normal incidence, dome/pillar morphology was observed and it evolved to step/terrace morphology as the incident angle approached 40°. The smoothest ion bombarded surfaces were observed at grazing angles.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Mechanics of Materials
- Mechanical Engineering
- Electrical and Electronic Engineering