Vibrational properties of two boron atoms in silicon - art. no. 073202

We systematically investigated the vibrational properties and total energy of defects containing two boron atoms in Si by a first-principles calculati on. Our calculations were performed for six configurations with two substit utional B atoms, including up to the fifth-nearest neighbors, which are fou nd to be electrically active, and for the (001) B-2 cluster. The total ener gy calculation reveals that two substitutional boron atoms prefer configura tions remote from each other because of tensile stress. Comparing calculate d IR frequencies and isotope shifts with experimental ones, we found that t he previous interpretation is inadequate for the vibrational modes of the f irst-nearest-neighbor B-2 cluster. Furthermore, it is shown that the theore tical IR peaks of (001) B-2 give a reasonable explanation for the experimen tal ones whose origin has not been clarified for more than 30 years. Thus t he existence of (001) B-2 is confirmed with respect to the atomic structure . We further calculated the electronic structure of(001) B-2, and found it to be consistent with near-edge x-ray absorption fine-structure spectroscop y data.