First-principles study of hydrogen incorporation in multivacancy in silicon

We report first-principles total-energy calculations which reveal microscop ic structures of multivacancies in Si and their feasibility of hydrogen inc orporation. We find that the hexavacancy V-6 and the decavacancy V-10 are s table, and that the multivacancies are capable of containing hydrogen atoms depending on its chemical potential. We also find that an H-2 molecule is trapped in the H-decorated multivacancy. The trapped H-2 molecule as well a s the Si-H bonds exhibit peculiar vibration spectra. Recent experimental da ta is interpreted on the basis of the present theoretical results.