Impact of local atomic stress on oxygen segregation at tilt boundaries in silicon

Using the atom probe tomography, transmission electron microscopy, and ab initio calculations, we investigate the three-dimensional distributions of oxygen atoms segregating at the typical large-angle grain boundaries (GBs) ( Σ 3 { 111 } , Σ 9 { 221 } , Σ 9 { 114 } , Σ 9 { 111 } / { 115 }, and Σ 27 { 552 }) in Czochralski-grown silicon ingots. Oxygen atoms with a covalent radius that is larger than half of the silicon's radius would segregate at bond-centered positions under tensile stresses above about 2 GPa, so as to attain a more stable bonding network by reducing the local stresses. The number of oxygen atoms segregating in a unit GB area N GB (in atoms/nm²) is hypothesized to be proportional to both the number of the tensilely-stressed positions in a unit boundary area n bc and the average concentration of oxygen atoms around the boundary [ O i] (in at. %) with N GB ∼ 50 n bc [ O i ]. This indicates that the probability of oxygen atoms at the segregation positions would be, on average, fifty times larger than in bond-centered positions in defect-free regions.