SURFACE-STATE TRANSITIONS ON THE RECONSTRUCTED DIAMOND C(100) SURFACE

The diamond C(100) surface was investigated with a high-resolution ele ctron energy loss spectrometer (HREELS) in both the electronic excitat ion and surface vibrational excitation regimes. The 0-15 eV electronic excitation spectra on the bare C(100) surface revealed three dominant loss features at 3.5, 4.7 and 5.9 eV. These peaks have been attribute d to two mid-gap surface states. These states were absent on the H-ter minated surface, indicating that they were localized at the surface an d were due either to pi-bonded dimers or dangling bonds on the surface . The separation between the states, and their possible positions rela tive to the valence band maximum, were compared to recent surface band structure calculations, and provide evidence for symmetric dimers on the C(100) surface. (C) 1998 Elsevier Science B.V.