Graphene nanomeshes are mainly produced through top-down lithography, resulting in unavoidable defects or contamination. In this article, we demonstrate a bottom-up approach through partial intercalation of fluorine between the carbon buffer layer and the underlying SiC (0001) substrate by low temperature annealing of a deposited molecular layer of fluorinated fullerenes C60F48. Due to the inherent periodicity of the bonding between the buffer layer and the underlying SiC (0001) substrate, selective fluorination and partial intercalation takes place. Using scanning tunneling microscopy and spectroscopy as well as density functional theory calculations, the existence of a graphene nanomesh with the local atomic arrangement of a graphene sheet and surface corrugation of long-range periodicity is revealed. Surprisingly, the nanomesh exhibits electronically an intermediate state between the conventional buffer layer, and quasi-free-standing graphene. Specifically, unlike the buffer layer, which is bonded covalently to the SiC (0001) surface so that the characteristic graphene π network about the K point of the Brilluoin zone is destroyed, this intermediate state retains the wavefunction characteristics of graphene, but a two peak structure in the local density of states (LDOS) is introduced about the K point. This graphene nanomesh with a two peak LDOS structure about the K point presents another playground for the study of transport properties in supported two-dimensional materials.
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This research is supported by the Institute of Materials Research and Engineering, A*STAR. Grant number is not applicable. KHK and SYQ gratefully acknowledge S. Kim and Y.-W. Son for providing the relaxed atomic coordinates for the buffer layer, as well as support from the Singapore National Research Foundation under grant NRF-NRFF2013-07.