  We demonstrate the local oxidation nanopatterning of graphene films by an
atomic force microscope. The technique provides a method to form insulating
trenches in graphene flakes and to fabricate nanodevices with sub-nm precision.
We demonstrate fabrication of a 25-nm-wide nanoribbon and sub-micron size
nanoring from a graphene flake. We also found that we can write either trenches
or bumps on the graphene surface depending on the lithography conditions. We
attribute the bumps to partial oxidation of the surface and incorporation of
oxygen into the graphene lattice.
