Bifurcation and Deviation of Cleavage Paths at Through-Thickness Grain Boundaries

The behavior of cleavage crack fronts at grain boundaries in free-standing silicon thin films is investigated through a microtensile experiment. In addition to the crystallographic orientation, the orientation of grain boundary plane also plays a critical role. With respect to the initial crack surface, if the inclination angle is relatively small, the crack tends to penetrate across the boundary; if the angle is large, the crack may either bifurcate along the boundary or turn back on another crystallographic plane. The former is triggered by crack front transmission, and the latter may result in a higher critical crack growth driving force.