Extended Point Defect Structures at Intersections of Screw Dislocations in Si: A Molecular Dynamics Study

Molecular dynamics computer simulations have been employed with the Tersoff interatomic potential to examine the atomic structure of (a=2) h110i screw dislocations forming regular two-dimensional arrays in silicon. The main attention is focused on the atomic configurations of dislocation intersections. The dislocations are assumed to be undissociated, following HREM observations on the low-angle (001) twist boundaries produced by silicon wafer bonding in ultrahigh vacuum. It is shown that cores of the dislocation intersections are formed by closed characteristic groups of atoms (extended point defects). The symmetry of these defects strongly depends on the fact whether the screw dislocation arrays generate a twist or a shear boundary.