@article{MaassUtechtStremlauetal.2017,
  author    = {Maass, Friedrich and Utecht, Manuel Martin and Stremlau, Stephan and Gille, Marie and Schwarz, Jutta and Hecht, Stefan and Klamroth, Tillmann and Tegeder, Petra},
  title     = {Electronic structure changes during the on-surface synthesis of nitrogen-doped chevron-shaped graphene nanoribbons},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {96},
  journal   = {Physical review : B, Condensed matter and materials physics},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-9950},
  doi       = {10.1103/PhysRevB.96.045434},
  pages     = {7},
  year      = {2017},
  abstract  = {Utilizing suitable precursor molecules, a thermally activated and surface-assisted synthesis results in the formation of defect-free graphene nanoribbons (GNRs), which exhibit electronic properties that are not present in extended graphene. Most importantly, they have a band gap in the order of a few electron volts, depending on the nanoribbon width. In this study, we investigate the electronic structure changes during the formation of GNRs, nitrogen-doped (singly and doubly N-doped) as well as non-N-doped chevron-shaped CGNRs on Au(111). Thus we determine the optical gaps of the precursor molecules, the intermediate nonaromatic polymers, and finally the aromatic GNRs, using high-resolution electron energy loss spectroscopy and density functional theory calculations. As expected, we find no influence of N-doping on the size of the optical gaps. The gap of the precursor molecules is around 4.5 eV. Polymerization leads to a reduction of the gap to a value of 3.2 eV due to elongation and thus enhanced delocalization. The CGNRs exhibit a band gap of 2.8 eV, thus the gap is further reduced in the nanoribbons, since they exhibit an extended delocalized pi-electron system.},
  language  = {en}
}
@article{UtechtPalmerKlamroth2017,
  author    = {Utecht, Manuel Martin and Palmer, Richard E. and Klamroth, Tillmann},
  title     = {Quantum chemical approach to atomic manipulation of chlorobenzene on the Si(111)-7 x 7 surface},
  series = {Physical review materials},
  volume    = {1},
  journal   = {Physical review materials},
  number    = {2},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2475-9953},
  doi       = {10.1103/PhysRevMaterials.1.026001},
  pages     = {5},
  year      = {2017},
  abstract  = {We present a cluster model to describe the localization of hot charge carriers on the Si(111)-7 x 7 surface, which leads to (nonlocal) desorption of chlorobenzene molecules in scanning tunneling microscope (STM) manipulation experiments. The localized charge carriers are modeled by a small cluster. By means of quantum chemical calculations, this cluster model explains many experimental findings from STM manipulation. We show that the negative charge is mainly localized in the surface, while the positive one also resides on the molecule. Both resonances boost desorption: In the negative resonance the adatom is elevated; in the positive one the chemisorption bond between the silicon surface adatom and chlorobenzene is broken. We find normal modes promoting desorption matching experimental low-temperature activation energies for electron-and hole-induced desorption.},
  language  = {en}
}