Damage nucleation and vacancy-induced structural transformation in Si grain boundaries

Atomic resolution Z-contrast scanning transmission electron microscopy reve als preferential nucleation of electron-beam-induced damage in select atomi c columns of a Si tilt grain boundary. Atomic scale simulations find that t he region of initial damage nucleation corresponds to columns where the for mation energies of vacancies and vacancy complexes are very low. The calcul ations further predict that vacancy accumulation in certain pairs of column s can induce a structural transformation to low-density dislocation "pipes" with all atoms fourfold coordinated. (C) 1999 American Institute of Physic s. [S0003-6951(99)00742-1].