Carbon segregation at Σ3 {1 1 2} grain boundaries in silicon

Abstract First-principles calculations were carried out to systematically investigate the carbon segregation along Σ3 {1 1 2} grain boundaries (GBs) in silicon. The energetically favorable segregation sites and corresponding segregation energy at two types of Σ3 {1 1 2} GBs, i.e. symmetric and asymmetric Σ3 {1 1 2}, were determined. A site-selective carbon segregation behavior along these two GBs was revealed, and a maximum segregation energy of −0.418 eV/atom and −0.525 eV/atom was predicted for the symmetric and asymmetric Σ3 {1 1 2} GBs, respectively. It is found that the segregation energy is linearly correlated with the average bond length (ABL) of carbon atoms segregating at the core sites in these two GBs instead of the ABL of core Si sites in the pristine Σ3 {1 1 2} GBs. Such a correlation is primarily attributed to the bonding energy effect caused by the substitution of carbon atom at the Σ3 {1 1 2} GBs, as well as the structural reconstructions of GBs along the [1 1 ¯ 0] direction. This work provides, at the atomic level, a fundamental theoretical understanding on the carbon segregation behavior at Σ3 {1 1 2} GBs in Si.