Hydrogen molecules trapped by multivacancies in silicon

We report an observation of a Raman line of H-2 in silicon after Si+-ion implantation followed by a hydrogen atom treatment. The vibrational frequency of the H-2 is 3822 cm(-1) between the two different vibrational frequencies, 4158 and 3601 cm(-1), of H-2 observed so far in silicon. The assignment is confirmed by the observation of isotope shifts to 2770 cm(-1) for D-2 and to 3353 cm(-1) for HD. The ion-fluence dependence of the Raman intensity of the H-2 at 3822 cm(-1) correlates with the total intensity of peaks in the Si-H stretching region that are attributed to H-terminated dangling bonds in multivacancies and/or interstitial-H complexes. We propose that the hydrogen molecule corresponding to the 3822 cm(-1) vibrational line is trapped in or adjacent to H-terminated multivacancies. [S0163-1829(99)12739-5].