Irregular cleavage front transmission at grain boundaries in free-standing polysilicon thin films was reported. When the orientations of 2 adjacent grains were correlated, the crack could bypass the boundary via a so-called tunnelling process. Similar behavior could also be achieved if the crack path curves in the grain-boundary-affected zone. Moreover, the separation of crack flanks could be aided by secondary cracking. These irregular modes of crack front behavior tended to lower the effective boundary toughness.

Secondary Cracking at Grain Boundaries in Silicon Thin Films. J.Chen, Y.Qiao: Scripta Materialia, 2007, 57[12], 1069-72