ELECTRONIC SRUCTURE OF THE ROOT-3X-ROOT-3-ALPHA AND 3X3 PERIODICITIESOF SN GE(111)/

Angle-resolved photoemission shows that the root 3 x root 3 and the 3 x 3 surfaces have almost identical surface band structures with two di spersive bands, one of which crosses the Fermi level. The close resemb lance between the electronic structures strongly points to a common at omic structure which is further supported by the two Sn 4d core-level components observed for both the root 3 x root 3 and the 3 x 3 surface s. The existence of two surface state bands on the root 3 x root 3 sur face calls for there evaluation of the T-4 model for Sn/Ge(111) and ot her related group IV adatom surfaces.