Graphene nanoribbon superlattices fabricated via He ion lithography.

Single-step nano-lithography was performed on graphene sheets using a helium ion microscope. Parallel "defect" lines of ~1 lm length and ≈5 nm width were written to form nanoribbon gratings down to 20 nm pitch. Polarized Raman spectroscopy shows that crystallographic orientation of the nanoribbons was partially maintained at their lateral edges, indicating a high-fidelity lithography process. Furthermore, Raman analysis of large exposure areas with different ion doses reveals that He ions produce point defects with radii ~2× smaller than do Ga ions, demonstrating that scanning- He^þ-beam lithography can texture graphene with less damage. [ABSTRACT FROM AUTHOR]