Fermi surface of Si(111)7X7

Surface states at the Si(111)7x7 surface are mapped by angle-resolved photoemission with E, theta multidetection. The adatom states near the Fermi level form a well-defined, two-dimensional energy surface consisting of closed loops that nearly fill the 7x7 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 1x1 cell, the loops centered at <(Gamma)over bar>(7x7)=(2/7,0) and <(Gamma)over bar>(7x7)=(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.