  We report nanoscale patterning of graphene using a helium ion microscope
configured for lithography. Helium ion lithography is a direct-write
lithography process, comparable to conventional focused ion beam patterning,
with no resist or other material contacting the sample surface. In the present
application, graphene samples on Si/SiO2 substrates are cut using helium ions,
with computer controlled alignment, patterning, and exposure. Once suitable
beam doses are determined, sharp edge profiles and clean etching are obtained,
with little evident damage or doping to the sample. This technique provides
fast lithography compatible with graphene, with ~15 nm feature sizes.
