The electro-mechanical behavior of sputter-deposited Mo thin films on flexible substrates

The electro-mechanical performance of Mo thin films grown by dc magnetron sputter deposition on polyimide substrates was investigated. A series of 500 nm thick Mo films was synthesized at different discharge powers to evaluate the effect of deposition conditions on the structure-stress relationship and to correlate the intrinsic properties of the Mo films with their electro-mechanical response. Different in-situ fragmentation tests were performed to assess the crack morphology, the change in electrical resistance and the film stress during straining. A direct relation between the residual stress state of the Mo thin films and the discharge power was noticed as the stress changed from tensile to compressive with increasing discharge power. All Mo films showed brittle fracture when strained in tension and the critical crack onset strain correlated with the residual stress state. In-situ synchrotron diffraction experiments enabled the characterization of the fracture strength, which was unaltered by the discharge power and found to be approximately 1700 MPa for all Mo thin films studied.