The topography and dislocation structure of a 6 [001] bi-crystal were studied by means of diffraction-contrast transmission electron microscopy. Saw-tooth arrays, comprising facets with lengths of a few tens of nm, were observed in each of 2 widely-separated sections of the boundary. The facet planes were {110}, {310} and {221}. Further sub-faceting of the (130) facets into a nm-scale saw-tooth configuration of (010) and (110) facets could produce an hierarchy of facets. The dislocation content which was measured in each type of defect agreed well with Frank’s formula. On the other hand, the dislocation content in each type of facet was inhomogeneously distributed; in contrast to the assumption of evenly spaced dislocations that was applied to boundaries of infinite extent. Certain types of dislocation were repeatedly grouped near to the facet centers and ends. Well-separated partial dislocations were frequently observed near to the facet mid-section, but not near to the facet junctions. An extended (about 30nm) strain contrast was observed at all of the junctions which were formed by facets with dimensions of the order of tens of nm.

I.F.Tsu, S.E.Babcock, D.L.Kaiser: Journal of Materials Research, 1996, 11[6], 1383-97