Role of Surface Reconstructions in (111) Silicon Fracture

The (111) cleavage in crystalline silicon was investigated by hybrid quantum/ classical atomistic simulations showing that its remarkable stability is largely due to asymmetric pi-bonded reconstructions of the cleavage surfaces created by the advancing crack front. Further simulations show that the same reconstructions can induce an asymmetric dynamical response to added shear stress components. This explains why [2 (1) over bar(1) over bar] upward steps are much more common than [(2) over bar 11] downward steps on (111) cleavage surfaces, while zigzag'' cleavage with alternated (111) and (11 (1) over bar) facets will still occur in crystal samples fractured under [110] uniaxial loading.