Hydrogen molecules trapped by multivacancies in silicon

We report an observation of a Raman line of H2 in silicon after Si+-ion implantation followed by a hydrogen atom treatment. The vibrational frequency of the H2 is 3822 cm-1 between the two different vibrational frequencies, 4158 and 3601 cm-1, of H2 observed so far in silicon. The assignment is confirmed by the observation of isotope shifts to 2770 cm-1 for D2 and to 3353 cm-1 for HD. The ion-fluence dependence of the Raman intensity of the H2 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