Top or underneath? Revealing the structure of multilayer graphene domains with atomic force microscopy and theoretical analysis

The structure of multilayer graphene domains on Cu foil is revealed with atomic force microscopy and theoretical analysis. The phase images of force microscopy enable the separation of the graphene domains from the naked areas of Cu foil. Furthermore, the phase images enable the discrimination of the different graphene layers and structures. For example, some of small graphene layers show a darker phase contrast than the surrounding single layer districts while other small layers have a brighter contrast with respect to the surrounding single layer areas. Then, we proceed to determine whether the few-layer graphene domains are wedding cake (WC) or inverted wedding cake (IWC) structures. The graphene samples with the artificial WC, IWC and sandwich structure were fabricated on Cu through layer by layer method. Based on the results of the artificial structures, we can know that the areas showing darker contrast in the as-grown samples correspond to the WC structure and the areas showing bright contrast are the IWC domains. Theoretical discussions disclose that the different energy dissipated on Cu or the respective graphene layer is responsible for the variation of the phase contrast.