Bulk silicon is susceptible to fatigue

It has long been held that bulk silicon is immune from fatigue. We present contrary evidence demonstrating severe fatigue in macroscale cracks produced in cyclic loading of single-crystal silicon with a sphere indenter. The key ingredient is a component of shear stress acting on the cracks during contraction and expansion of the contact circle. This gives rise to frictional sliding at the crack walls, dislodging and ejecting slabs of material and debris onto the silicon surface. The damage expands with continued cycling, leading to progressive degradation of the surface. The results have implications concerning the function of silicon-based devices.