First principles total energy calculations of the adsorption of Cl, Cl2, and HCl on Ge(0 0 1)-c(2×4)

We have performed first principles total energy calculations to investigate the adsorption of Cl, Cl2, and HCl on the Ge(0 0 1)-c(2×4) surface. Based on previous experimental and theoretical results of Cl on Si(0 0 1), we have considered two different geometries for the adsorption of a single Cl atom on Ge(0 0 1). We have found that the most stable configuration corresponds to adsorption of the Cl atom along the dangling bond of a Ge atom. This geometry is similar to the one formed by a Cl atom on Si(0 0 1). For the adsorption of a Cl2 molecule, several geometries were considered. First of all, our results indicate that the adsorption of Cl2 as a molecule is not energetically favorable. Instead, Cl2 dissociates into two Cl subunits. The most stable geometry was achieved when each Cl subunit is bonded to a Ge atom of the same surface dimer, along the dangling bonds. Finally we have considered the adsorption of a single HCl molecule. Again, several geometries were tested. Similar to Cl2, adsorption of HCl as a molecule is not energetically favorable. Again, the most stable structure was obtained when HCl dissociates in to H and Cl subunits, and they are adsorbed along the dangling bonds of the same Ge-dimer.