Confinement of Dirac electrons in graphene quantum dots

We observe spatial confinement of Dirac states on epitaxial graphene quantum dots with low-temperature scanning tunneling microscopy after using oxygen as an intercalant to suppress the surface state of Ir(111) and to effectively decouple graphene from its metal substrate. We analyze the confined electronic states with a relativistic particle-in-a-box model and find a linear dispersion relation. The oxygen-intercalated graphene is p doped [ED=(0.64±0.07) eV] and has a Fermi velocity close to the one of free-standing graphene [vF=(0.96±0.07)×106 m/s]