ADSORBATE-INDUCED DE-RECONSTRUCTION IN THE INTERACTION OF H2S WITH GE(001) 2X1

The room temperature adsorption of H2S on Ge(001) 2 x 1 has been studied using surface-extended x-ray-absorption fine structure, low-energy electron diffraction and Auger electron spectroscopy. The Ge(001) 2 x 1-S system formed by a saturation dose followed by an anneal to remove H has a S-Ge bond length of 2.36 +/- 0.05 angstrom, with S sitting in twofold bridge sites, consistent with breaking of the Ge-Ge dimer reconstruction. Further adsorption of H2S at low or elevated temperatures is kinetically unfavourable, and it is proposed that this is consistent with the surface Ge atoms sitting in non-ideal rather than bulk-terminated positions.