The electronic structure of nanographene depends on its edge geometry. In zigzag-edged nanographenes, nonbonding edge state is created around the edge region. This is a consequence of broken symmetry of pseudo-spin in the massless Dirac fermion, or it is understood in terms of degraded aromaticity. The large LDOS populated around edges and its strong spin polarization cause electronic/chemical/magnetic activities. In armchair-edged nanographene, the inter-valley scattering creates a standing wave, or we can understand it on the basis of fully benzenoid structure. We investigate the geometry-dependent electronic structure using STM/STS, AFM and Raman spectra. STM/STS observations show the presence of edge state in well defined zigzag edges. Raman spectra and STM observations confirm the presence of a standing wave in armchair-edged nanographene. Systematic STM observations of various graphene nanostructures embedded in graphene oxide allow us to understand the geometry dependent electronic structure in terms of Clar's aromatic sextet rule.

Edge geometry and electronic structure of nanographene

245th National Meeting (2013)

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