Recent theoretical work found that isolated As impurities in Ge grain boundaries exhibit minimal binding, leading to the suggestion that the observed segregation is likely to occur at defects and steps. We report ab initio calculations for As in Si and show that segregation is possible at defect-free boundaries through the cooperative incorporation of As in threefold-coordinated configurations: As dimers, or ordered chains of either As atoms or As dimers along the grain boundary dislocation cores. Finally, we find that As segregation may drive structural transformations of certain grain boundaries.

• Received 25 March 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.1306