Ge-derived Si(1 1 1)(7 × 7) structure studied by low-energy electron diffraction and angle-resolved electron-energy-loss spectroscopy

Abstract

Using low-energy electron diffraction (LEED) and angle-resolved electron-energy-loss spectroscopy (AR-EELS), we find that a new Ge-derived Si(7 × 7) superstructure is formed as the stable surface phase at a Ge coverage of 1.5 monolayers. A new surface one-electron transition appears at 1.15 eV ( at δk| ( the momentum transfer) = 0 A ̊ −1 ) and the Si dangling bond surface state transition at 1.5 eV ( at δk| = 0 A ̊ −1 ) disappears, while loss peaks due to SiSi back-bond surface states still remain. We ascribe the new peak to the Ge dangling-bond surface state transition and propose that the Ge atoms substitute the Si surface atoms which have surface dangling bonds.