Structure and Effects of Vacancies in Sigma3 (112) Grain Boundaries in Si

Using the first-principle density-functional theory, we study the structure and effects of vacancies in σ3 (112) grain boundary with the coincident-site lattice structure in Si. We find that the formation energy for a Si vacancy in the grain boundary is significantly lower than that in Si perfect region, indicating strong segregation of Si vacancy in grain boundary regions. The formation of Si vacancies in grain boundaries either cleans up the deep levels or facilitates complete passivation by H atoms. Our results suggest that vacancies in grain boundaries may play important role in determining grain boundary physics and passivation behavior.