Defect induced modification of the surface gap and optical properties of C(111)2 X 1 surface

To resolve the long standing controversy between experimentally measured reflectance anisotropy (RA) of C(111)2 x 1 surface and theoretically calculated optical response, we demonstrated that defects at the C(111) surface in the form of minor hydrogen contamination, missing carbon atoms and/or terraces can be responsible for the appearance of the gap between the surface states, which is absent for the Pandey reconstructed ideal C(111)2 x 1. Ab initio DFT LDA calculations for such non-ideal systems indeed demonstrate that even 6% of residual hydrogen (which is below the standard experimental detection limits) or 40 angstrom wide terraces are enough to sufficiently open the surface gap and account for the observed optical anisotropy. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim