Abstract
We studied optical absorption spectra of Si crystals grown in a hydrogen ambient. Specimens were grown by the floating-zone growth method in a hydrogen ambient of 1 atm. Optical absorption spectra of those specimens were measured at 6 K. Many optical absorption lines were observed in the range of 1900–2200 cm−1. They were observed only when the concentrations of carbon or boron were high. To understand these results, we referred to a report according to which a so-called A-type swirl, an interstitial-type dislocation loop, was observed when impurities of smaller covalent radii than that of Si were doped. Hence, we concluded that the above optical absorption lines were due to localized vibration of hydrogen atoms bound to interstitial Si atoms.