Surface state on the SiC(0001)-(root 3x root 3) surface

An angle resolved photoemission study of a surface state on the SiC(0001)-(root 3 x root 3) surface is reported. Experiments carried out on the 6H and 4H polytypes give essentially identical results. A surface state band with semiconducting occupation is observed, centered around 1.0 eV above the valence band maximum VBM and with a width of about 0.2 eV, Recently calculated results for a Si-adatom-induced root 3 x root 3 reconstruction give a metallic surface state band centered about 1.3 eV above the VBM and with a width of 0.35 eV. The dispersion determined experimentally is smaller than calculated but exhibits the same trend, the surface state disperses downwards towards the VBM with increasing parallel wavevector component along both the <(Gamma) over bar>-(M) over bar and <(Gamma) over bar>-(K) over bar; directions of the root 3 x root 3 Surface Brillouin zone. The VBM is determined to be located at about 2.(+/-0.2) eV below the Fermi level. The results indicate that Si adatoms on top of an outermost SI-C bilayer mag. be an inadequate structural model for explaining recent experimental findings for the SiC(0001)-(root 3 x root 3) surface.