Jm. Themlin et al., UNOCCUPIED SURFACE-STATE ON THE (ROOT-3X-ROOT-3) R30-DEGREES RECONSTRUCTION OF 6H-SIC(0001), Europhysics letters, 39(1), 1997, pp. 61-66
Applying k-resolved inverse photoemission (KRIPES) to the root 3 x roo
t 3 R30 degrees-reconstructed 6H-SiC(0001) face, we have observed a sh
arp surface state U located at 1.10 +/- 0.05 eV above the Fermi level
at the centre of the surface Brillouin zone. Its bandwidth of 0.34 +/-
0.05 eV is in good agreement with the 0.35 eV predicted by first-prin
ciple calculations based on a Si-adatom model. However, LDA calculatio
ns predict a half-filled Sigma(1) state and a metallic character for t
his reconstruction. Together with recent ARUPS data, our results revea
l that the one-electron band Sigma(1) is split into two bands, giving
a semiconducting surface with a reduced indirect bandgap around 2.0 eV
at the <(K)' over bar> point. Many-body correlation effects may give
rise, in the limit of strong localization, to this bandgap opening.