Whether photoemission probes surface or bulk properties has long been a topic of interest and debate. This work employs angle-resolved photoemission to map the electronic structure of Ag films of varying thicknesses prepared on Si(111). As expected, the discrete quantum-well states or subbands observed at small thicknesses merge into a continuum as the film thickness approaches the bulk limit. However, a number of discrete states remain isolated within gaps or pockets in the bulk continuum. While these Ag surface states have been predicted previously by calculations, most are experimentally identified herein only for the first time. Copyright (C) EPLA, 2009

We have systematically investigated the effect of oxidation on the structural and electronic properties of graphene based on first-principles calculations. Energetically favorable atomic configurations and building blocks are identified, which contain epoxide and hydroxyl groups in close proximity with each other. Different arrangements of these units yield a local-density approximation band gap over a range of a few eV. These results suggest the possibility of creating and tuning the band gap in graphene by varying the oxidation level and the relative amount of epoxide and hydroxyl functional groups on the surface.

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