A new methodology to investigate fracture toughness of freestanding MEMS and advanced materials in thin film form

Abstract—This paper presents a novel membrane deflection fracture experiment (MDFE) to investigate the fracture tough-ness of microelectromechanical systems (MEMS) and other advanced materials in thin film form. It involves the stretching of freestanding thin-film membranes, in a fixed-fixed configu-ration, containing preexisting cracks. The fracture behavior of ultrananocrystalline diamond (UNCD), a material developed at Argonne National Laboratory, is investigated to illustrate the methodology. When the fracture initiates from sharp cracks, produced by indentation, the fracture toughness was found to be 4 5 0 25 MP m 1 2. When the fracture initiates from blunt notches with radii about 100 nm, machined by focused ion beam (FIB), the mean value of the apparent fracture toughness was found to be 6.9 MPa m1 2. Comparison of these two values, using the model proposed by Drory et al. [9], provides a correc-tion factor of two-thirds, which corresponds to a mean value of 2 = 1 2. [1083] Index Terms—Fracture toughness, microelectromechanical sys-tems (MEMS), thin films, ultrananocrystalline diamond. I