Atomic and electronic-band structures of anomalous carbon dimers on 3C-SiC(001)-c(2 x 2)

The atomic structure of the c(2 X 2) reconstruction of the C-terminated 3C- SiC(001) surface was unambiguously determined by scanning tunneling microsc opy and surface-core-level-resolved photoelectron diffraction studies. This surface is found to uniquely and uniformly consist of anomalous bridge-bon ded C dimers with a C-C bond length of 1.22 Angstrom. Furthermore, an exten sive angle-resolved photoemission study clearly identifies two occupied pi state bands due to the surface-normal and -parallel pi orbitals of the trip le-bonded C dimers. This provides an electronic explanation of the stabilit y of this unique surface reconstruction.