Atomic configurations and energetics of arsenic impurities in a silicon grain boundary

We report direct atomic-resolution Z-contrast imaging of arsenic impurities segregated in specific atomic columns in a silicon grain boundary. Through a combination of image intensity analysis, first-principles calculations, and statistical mechanics, we establish that segregation occurs in the form of isolated dimers. The formation of As dimers in the boundary is shown to be favored over ordered chains by entropic considerations and kinetic constraints. The observed segregation is consistent with known solubilities.