Ab initio calculations of a vacancy in a Ge nano-cluster and its passivation with atomic and molecular hydrogen

Abstract The mechanism of passivation of germanium vacancies by atomic and molecular hydrogen is investigated at the atomic level by employing ab initio calculations. The deformation provoked by the reconstruction of Ge–Ge dangling bonds is found to propagate in to the network beyond the second neighbors of the vacancy. The structures of the partially passivated vacancies (VH n , n =1,2,3 and 4) are also calculated. For a VH 1 , a 3-center-3-electron structure is found. It is also found that the reconstruction of a Ge–Ge bond in these hydrogen passivated VH n vacancies is, to a certain extent, controlled by the degree of distortion allowed by the covalent bonds between Ge atoms. The passivation of the vacancy by molecular hydrogen is also studied. The calculations indicate that a VH 3 vacancy cannot be passivated by a H 2 molecule. The energetics calculated for the Ge–Ge bond reconstruction is discussed.