H₂S exposure of (100)Ge surface: Evidences for a (2x1) electrically passivated surface

The experimental study of the bonding geometry of a (100)Ge surface exposed to H₂S in the gas phase at 330 °C shows that 1 ML S coverage with (2x1) surface reconstruction can be achieved. The amount of S on the Ge surface and the observed surface periodicity can be explained by the formation of disulfide bridges between Ge-Ge dimers on the surface. First-principles molecular dynamics simulations confirm the preserved (2x1) reconstruction after dissociative adsorption of H₂S molecules on a (100)Ge (2x1) surface, and predict the formation of (S-H)-(S-H) inter-Ge dimer bridges, i.e., disulfide bridges interacting via hydrogen bonding. The computed energy band gap of this atomic configuration is shown to be free of surface states, a very important finding for the potential application of Ge in future high performance integrated circuits.