Dynamical fluctuation and surface phase transition at the SnrGe 111/ 63=63R308-a interface

The 63=63R308-a surface phase of SnrGe 111. transforms reversibly upon cooling into a 3=3 phase. Using high-resolution photoemission, the effect of this transition on the Sn core-level and the Fermi surface FS. has been determined. The topology of the FS show a Fermi momentum along G K and G M of 0.27"0.02 A°y1 and 0.30"0.02 A°y1, respectively. In the low-temperature phase, a well-resolved core-level splitting is observed for the Sn adatoms. Our data are consistent with a local-bonding representation, where the transition is driven by freezing of dynamic fluctuations of two inequivalent types of Sn adatoms, coexisting at room temperature. q2000 Elsevier Science B.V. All rights reserved