Atomic configurations, stability, and impurity vibrations of carbon-oxygen complexes in silicon

We investigated the atomic configurations, stabilizing mechanism, and impurity vibrations of carbon-oxygen (C-O) complexes in crystalline silicon both theoretically (by calculating total energy using norm-conserving pseudopotentials), and experimentally (by measuring low-temperature infrared absorption). We found that the second neighbor interstitial site of a substitutional carbon atom is more stable for an oxygen atom than the first neighbor site. Lattice relaxation is essential to this stability. The calculations on the impurity vibrations of the C-O complex of the second-neighbor configuration closely agree with the experimental results. The existence of several kinds of C-O complexes with different configurations, which is suggested by the calculations, was confirmed by experiment.