Direct nano-patterning of graphene with helium ion beams

Helium ion microscopy (HIM) was used for direct nano-patterning of single-layer graphene (SLG) on SiO2/Si substrates. This technique involves irradiation of the sample with accelerated helium ions (He+). Doses of 2.0 x 10(16) He+ cm(-2) from a 30 kV beam induced a metal-insulator transition in the SLG. The resolution of HIM patterning on SLG was investigated by fabricating nanoribbons and nanostructures. Analysis of scanning capacitance microscopy measurements revealed that the spatial resolution of HIM patterning depended on the dosage of He+ in a non-monotonic fashion. Increasing the dose from 2.0 x 10(16) to 5.0 x 10(16) He+ cm(-2) improved the spatial resolution to several tens of nanometers. However, doses greater than 1.0 x 10(17) He+ cm(-2) degraded the patterning characteristics. Direct patterning using HIM is a versatile approach to graphene fabrication and can be applied to graphene-based devices. (C) 2015 AIP Publishing LLC.