Atomic scale displacement field induced by a near-Σ9 twin boundary in silicon

Abstract

The structure of a near-Sigma 9 symmetrical tilt boundary of a silicon bicrystal is observed at atomic scale by high-resolution transmission electron microscopy using the [0,1,1] common tilt axis. The experimentally observed positions of atomic rows nearby the boundary are compared to theoretically predicted row positions using an elastic displacement field u generated by a planar semicoherent interface containing a periodic array of edge DSC dislocations. These dislocations accommodate a small angular departure (1.70 degrees) fromthe perfect Sigma 9 twin orientation, as a small-angle symmetrical tilt grain boundary accommodates the misorientation. The investigation includes a large region containing two successive dislocation cores (spacing 6.1 nm). A good agreement between the experimental and theoretical atomic rows is obtained, except in the vicinity of the dislocation cores. This observation shows that the elastic field of the DSC dislocation array behaves like that of a planar periodic semicoherent interface separating two different crystals: it does not generate a long-range displacement or rotation field. (C) 2016