Electronic transport and layer engineering in multilayer graphene structures

We demonstrate a reproducible layer engineering technique for multilayer graphene through controllable oxidation via a SiO2 capping layer. The oxidation method is able to reduce the thickness of few layer graphene to a single layer, as determined by a combination of contrast and Raman spectroscopies. We have also studied the electrical transport properties of graphene sheets with different thicknesses by focusing on their minimum conductivity. The average minimum conductivity of single layer graphene was found to be 0.3×4e2∕h, while that of multilayer graphene consisting of n layers is approximately 1.2×4e2∕h for n=2, 2.4×4e2∕h for n=3, and 4ne2∕h for n>3. The results suggest that the substrate plays an important role in determining the transport properties of thin graphene sheets with n<3, while its influence is relatively small in thicker graphene sheets.