First-principles calculations were made of the vibrational properties and total energy of defects which contained two B atoms. The calculations were performed for 6 configurations of 2 substitutional B atoms, and included neighbours up to fifth-nearest. These were found to be electrically active. The <001>B2 cluster was also studied. The total energy calculations revealed that 2 substitutional B atoms preferred configurations which were remote from each other, because of tensile stresses. By comparing calculated infra-red frequencies and isotope shifts with experimental ones, it was found that previous interpretations were inadequate for explaining the vibrational modes of the first-nearest neighbour B2 cluster. It was shown that the theoretical infra-red peaks of <001>B2 gave a reasonable explanation of the experimental data. The existence of <001>B2 was confirmed with regard to the atomic structure. The electronic structure of <001>B2 was found to be consistent with near-edge X-ray absorption fine-structure spectroscopic data.

Vibrational Properties of Two Boron Atoms in Silicon. J.Yamauchi, N.Aoki, I.Mizushima: Physical Review B, 2001, 63[7], 073202 (4pp)