Theoretical and isotopic infrared absorption investigations of nitrogen-oxygen defects in silicon

The vibrational spectroscopy of NNO defects in Si introduced by 16 O, 14 N and 15 N ion implantation is studied, and especially the N-isotopic shifts of the localized vibrational modes. These investigations show that the local modes of the three impurity atoms comprising the defect are only weakly coupled dynamically. Ab initio cluster calculations of the local mode frequencies of the defect are performed. Several models are investigated, and the model consisting of a bridging O atom adjacent to the N pair defect accounts for its dynamic properties.