Cleavage cracking across triple grain boundary junctions in freestanding silicon thin films

Abstract

This article is focused on a fractography study of cleavage cracking at triple grain boundary junctions in freestanding silicon thin films. At a triple junction, as the crystallographic orientations of the two grains ahead of the crack are different by only a few degrees, the cleavage front advance becomes quite jerky. The crack first enters the grain of smaller boundary toughness and then turns into the other grain from the lateral direction. Consequently, the overall fracture resistance cannot be analyzed in the framework of line-average theory. The nonuniform characteristic of crack behavior can be attributed to the increase in local stress intensity. A few typical crack front advance modes are identified.