Raman spectroscopy of hydrogen molecules in crystalline silicon

We report on a Raman spectroscopy study of float-zone crystalline silicon after exposure to a hydrogen plasma. New lines measured at 3601 and 2622 cm(-1) are attributed to vibrational excitations of H-2 and D-2 molecules, respectively, positioned at the tetrahedral interstitial site within the Si lattice. These results correct a recent identification of molecular hydrogen in Si and confirm recent calculations that the vibrational frequency of the H-2 molecule in Si will be reduced by several hundred wave numbers from the known value for the H-2 molecule in the gas state.