Substitutional oxygen-oxygen pair in silicon

The electronic structure and stability of an oxygen-oxygen pair occupying a single substitutional site in crystalline silicon are explored by the cluster scattered-wave Xα and the cluster modified neglect of diatomic overlap methods. These calculations support the existence of a stable 〈100〉-oriented pair, where the oxygens in the vacant lattice site are well separated and only weakly interacting. No electrical levels are found in the gap for the equilibrium configuration, which indicates that the oxygen pair completely passivates the vacancy dangling bonds while introducing no new electrical activity. We also consider the previous suggestion that a strain-confined version of the pair is the core of the thermal donor in silicon.