Surface electronic structure of Ge(111) from 300 to 1100 K by metastable deexcitation spectroscopy

Metastable atom deexcitation spectroscopy is applied to the study of the temperature dependence of the electronic structure of the Ge(111)c(2X8) surface. The present work is stimulated by the debate on temperature induced surface phase transitions. In this field the application of high surface sensitive atomic beam spectroscopy appears to be extremely promising. Metastable deexcitation spectra are taken in the 300-1100 K temperature interval, i.e., up to similar to 100 K below the bulk melting point. Spectra show a monotonic variation with temperature. Restatom and adatom contributions are identified and their evolution with temperature is followed. In particular, the persistence of the adatoms up to the highest investigated temperatures and the progressive metallization of the surface, already visible since 670 K, are observed. Data seem to indicate more agreement with surface models where order is preserved at high temperatures.