Phark, S.-H., Borme, J., Leon Vanegas, A., Corbetta, M., Sander, D., Kirschner, J.

Direct observation of electron confinement in epitaxial graphene nanoislands

ACS Nano

**5**, (10),pp 8162-8166 (2011)

One leading question for the application of graphene in nanoelectronics is how
electronic properties depend on the size at the nanoscale. Direct observation of the quantized
electronic states is central to conveying the relationship between electronic structures and local
geometry. Scanning tunneling spectroscopy was used to measure differential conductance dI/dV
patterns of nanometer-size graphene islands on an Ir(111) surface. Energy-resolved dI/dV maps
clearly show a spatial modulation, indicating a modulated local density of states due to quantum
confinement, which is unaffected by the edge configuration. We establish the energy dispersion
relation with the quantized electron wave vector obtained from a Fourier analysis of dI/dV maps. The
nanoislands preserve the Dirac Fermion properties with a reduced Fermi velocity.