Metastable triplet state of the vacancy-oxygen center in silicon: An ab nitio cluster study.

Abstract

An ab initio quantum chemical cluster study of the neutral vacancy-oxygen or (V-O${)}^{0}$ center in silicon, is presented, with emphasis on its metastable triplet state. We calculate a singlet-triplet splitting of 0.16 eV for (V-O${)}^{0}$. By calculation of the anisotropy of the nonradiative triplet life times we prove that the nonradiative decay occurs through combined spin-orbit and vibronic interaction. The observed ${\mathit{C}}_{2\mathit{v}}$ off-center displacement is shown to be an effect of chemical bonding. Relaxation effects of nearest-neighbor Si and local vibrational modes are studied. As a check on the approach we study the effect of cluster size and compare our theoretical values for the hyperfine interactions with $^{17}\mathrm{O}$ and the three nearest $^{29}\mathrm{Si}$ neighbor shells to experiment.