Vibrational absorption of carbon and carbon-oxygen complexes in silicon

Abstract

Vibrational absorption of isolated carbon and carbon-oxygen complexes has been studied in silicon containing various carbon isotopes. The energies of the isolated carbon fundamentals and second harmonics have been determined at 290° and 77°K and compared with the corresponding results for boron. The strength of the local mode absorption has been remeasured and the high value of η 0 ≅ 2.5 e has been confirmed. A search has been made for band mode absorption due to carbon with essentially negative results; this fits in with current theoretical ideas on long range impurity induced polarization effects in silicon. Satellite lines near the carbon fundamental at 588, 640 and 690cm −1 for 12C and corresponding lines for 13C and 14C have been correlated in strength with satellite lines at 1104 and 1052cm −1. The latter lines show no splitting or broadening at 4.2°K when different carbon isotopes are present and it is concluded that they are due to vibrations of oxygen in a centre where the rotational motion is quenched. Detailed models of possible C-O pair structures are discussed and compared with isolated oxygen and Li-O centres. It is concluded that the carbon atom in the pair probably occupies a second or third neighbour site to the interstitial oxygen.