Local vibrations of thermal double donors in silicon

The local vibrational modes (LVM’s) of the oxygen chains assigned to thermal double donors (TDD’s) and other related oxygen defects in silicon are studied using accurate total-energy calculations. We find that the calculated LVM frequencies as well as their isotopic shifts and charge-state dependences (temperature dependences) for the oxygen chains agree closely with the corresponding experimental quantities, which supports our assignments of the O2i−O2r chain to TDD1 and the Oi−Onr−Oi chains to TDDn (n>1) (Oi is an interstitial oxygen and Or a threefold coordinated oxygen belonging to a ring).