Adsorption of Molecular Oxygen onto Si1-xGex/Si(001) Surface

On the basis of ab initio calculations, the adsorption of O2 molecules onto a Si1-xGex/Si(001) surface has been considered at a qualitative level, and stable adsorption configurations of molecular oxygen have been determined. The O2 molecule was found to be chemisorbed without dissociation onto the Si1-xGex/Si(001) surface. In the case where the Si1-xGex/Si(001) surface is presented by pure Si-Si or mixed Si-Ge ad-dimers, the adsorption of O2 molecules was found to be barrierless. In the case where the surface is presented by pure Ge-Ge ad-dimers, the chemisorption barrier was found to be lower than 0.1 eV. The adsorption of O2 molecule on the Si1-xGex/Si(001) surface is accompanied by a change of the spin state of the system from the triplet to the singlet one and by a reduction of the surface chemical reactivity.