Halogen Interaction with the Ge(111) and Ge(100) Surfaces

A comparative study of the interaction of iodine and chlorine with Ge(111) and Ge(100) has been performed using photoelectron spectroscopy. On the Ge(111) surface both adsorbates preferentially occupy the on-top T-1 site. In addition small amounts of GeX2 species are found in bridge sites (X = I or Cl). On Ge(100)-I only Gel is formed at room temperature with one iodine atom on each dimer atom dangling bond. The halogen coverage at saturation has been estimated from survey spectra including both the Ge 3d and the I 4d or Cl 2p levels and from detailed Ge 3d spectra. These two approaches yield significantly different values; this discrepancy is interpreted as reflecting the presence of molecular species on top of the chemisorbed adlayer.