Understanding Size Effect in Cleavage Cracking in Thin Materials

In a specially designed tensile fracture experiment on bicrysal thin films, it was discovered that the fracture toughness of a thin film is not a material constant; rather, as the film becomes thinner it decreases much faster than the prediction of conventional theory. A detailed analysis revealed that this is caused by the mismatch of crystalline structures and, more importantly, with an appropriate crystalline orientation distribution the decrease may be suppressed. This result shed light on the fundamentals of crystal behaviors in pressurized matters. It also provides a promising solution to minimize unexpected failures in nano/micro-electromechanical systems, and therefore is of immense technological importance