Experimental and theoretical electronic structure determination of theβ−SiC(001)c(4×2)surface reconstruction

Abstract

We study the electronic band structure of the $\ensuremath{\beta}\text{\ensuremath{-}}\text{SiC}(001)c(4\ifmmode\times\else\texttimes\fi{}2)$ surface reconstruction by combined angle-resolved ultraviolet photoemission spectroscopy experiments and first principles electronic structure calculations. The experimental and theoretical dispersion curves are found to be in good agreement. Four occupied electronic surface states are found along the two high symmetry directions ($\overline{\ensuremath{\Gamma}}$-$\overline{\mathrm{J}}$ and $\overline{\ensuremath{\Gamma}}$-$\overline{{\mathrm{Y}}^{\ensuremath{'}}}$-$\overline{{\mathrm{J}}^{\ensuremath{'}}}$) of the surface Brillouin zone. The surface state located around $\ensuremath{\approx}1.5\phantom{\rule{0.3em}{0ex}}\text{eV}$ below the Fermi level displays a strong dispersion along the $\overline{\ensuremath{\Gamma}}\text{\ensuremath{-}}\overline{\mathrm{J}}$ direction and a weak dispersion along $\overline{\ensuremath{\Gamma}}$-$\overline{{\mathrm{Y}}^{\ensuremath{'}}}$-$\overline{{\mathrm{J}}^{\ensuremath{'}}}$. A weak coupling is found between up- and down-dimers belonging to two different adjacent dimer rows. The electronic structure is discussed in the context of the available real-space models for the $c(4\ifmmode\times\else\texttimes\fi{}2)$ reconstruction. The experimental band structure is inconsistent with a model of missing rows of asymmetric dimers (MRAD) while in reasonable agreement with the alternately up- and down-dimer (AUDD) model of the $\ensuremath{\beta}\text{\ensuremath{-}}\text{SiC}(001)c(4\ifmmode\times\else\texttimes\fi{}2)$ surface reconstruction.