HIGH ATOM DENSITY IN THE 1X1 PHASE AND ORIGIN OF THE METASTABLE RECONSTRUCTIONS ON SI(111)

We report unambiguous atomic scale evidence demonstrating that the ato m density in the '' 1 x 1 '' high temperature phase of Si(111) is appr oximately 6% higher than the 7 x 7. Such evidence is provided by scann ing tunneling microscopy observation of excess adatom density and rela ted island formation on surfaces prepared by a novel method which prov ides a low step density. The presence of the excess adatom density is also correlated to the observation of areas of metastable reconstructi ons, i.e., 9 x 9, 2 x 2, c2 x 4, and square-root 3 x square-root 3, mu ch larger than previously reported and for the first time, the existen ce of metastable 11 x 11 on Si(111).