Local vibrational modes of the metastable dicarbon center (C-s-C-i) in silicon

The metastable dicarbon center (C-s-C-i) in silicon has been studied by infrared absorption spectroscopy. After electron irradiation of carbon-doped silicon, new infrared absorption lines at 540.4, 543.3, 579.8, 640.6, 730.4, and 842.4 cm(-1) are observed. The lines are identified as local vibrational modes of the C-s-C-i center in its a form. Illumination of the sample with band-gap light at similar to 60 K converts the B to the A form, and local modes of the Pt form are identified at 594.6, 596.9, 722.4, 872.6, and 953 cm(-1). The observed local mode frequencies of both forms are in excellent agreement with those calculated from ab initio theory. Our findings provide strong support for the atomic structure suggested previously for the two forms. [S0163-1829(99)07635-3].