Adsorption of O adatoms on hydrogenated Si cluster

The adsorption of an O adatom on the most stable hydrogenated Si cluster (Si₆H₁₂) has been explored for the first time by using first principles. Two interesting adsorption configurations are found: In the first one, a striking feature is the substitutional adsorption: the O adatom forms a bond with a Si atom in the substrate cluster, which releases a H atom, and the H atom is in turn bonded to the adatom, exhibiting a similar feature to the Si adatom on the hydrogenated Si(100) surface. In the second one, the O adatom breaks the Si-Si bond and is bridge-bonded to two Si atoms, which not only exhibits the key structural feature for Si oxide clusters with ring and chain structure, but also displays the characteristics of oxidation of the Si(001) surface and oxygen impurities in bulk silicon. The latter structure is more stable than the former.