Chemical and structural analysis of sub-20 nm graphene patterns generated by scanning probe lithography

Abstract

We report a combination of force microscopy, high resolution TEM, focused ion beam nanolithography and high spatial resolution electron spectroscopies (Electron Energy Loss Spectroscopy (EELS) and Energy-Dispersive X-ray spectroscopy (EDX)) to characterize the structure and chemical composition of sub-4 nm in height and sub-20 nm in width patterns fabricated by oxidation scanning probe lithography on graphene. The spectroscopic analysis shows that the patterns contain C and O which confirms the existence of graphene oxide. The o-SPL patterns grow 1-3 nm above and below the graphene baseline. This also implies the local modification of the underneath SiC during the o-SPL patterning. However, by tuning the o-SPL oxidation parameters it is possible to restrict the modification to the graphene layer. The patterns have a trapezoidal shape dominated by the length of the base. We have shown that for the smallest and thinnest oxides (total thickness of about 2 nm), the shape is almost rectangular. This is important in order to define the real distance between the dielectric barriers in a quantum dot device.