Creating Nanohole Arrays with the Helium Ion Microscope

Helium Ion Microscopy has been established as a powerful imaging technique offering unique contrast and high resolution surface information. More recently, the helium ion beam has been used for nanostructuring applications similar to a gallium focused ion beam. A key difference between helium and gallium induced sputtering is the less intense damage cascade which lends this technique to precise and controlled milling of different materials enabling applications. The helium ion beam has been used for drilling 5nm holes in a 100nm gold foil (20: 1 aspect ratio) while the gallium beam sputtered holes of a similar aspect ratio seem to be limited to a 50nm hole size. This paper explores the drilling of nanopores in gold films and other materials and offers an explanation for the observed differences in results between helium and gallium ions.