Fermi surface ofSi(111)7×7

Abstract

Surface states at the $\mathrm{Si}\left(111\right)\mathrm{}7\times 7$ surface are mapped by angle-resolved photoemission with $E,\vartheta$ multidetection. The adatom states near the Fermi level form a well-defined, two-dimensional energy surface consisting of closed loops that nearly fill the $7\times 7$ unit cells. The width of the occupied adatom bands is 0.28 eV, twice as large as predicted by local density theory. Of the 49 possible locations inside the $1\times 1$ cell, the loops centered at ${\overline{\Gamma }}_{7\times 7}=(2/7,0)\mathrm{}$ and ${\overline{\Gamma }}_{7\times 7}=(3/7,-1/7)$ dominate in intensity, whereas those near (0,0) are suppressed by more than a factor of 20. These results provide quantitative input for characterizing narrow bands with substantial correlation effects at surfaces with large-scale reconstructions.