How Cracks Induced by Straining Influence the Tribological Properties of Mo Films Deposited on Polyimide Substrates

Abstract

Thin film materials used in flexible electronics are deposited on polymer substrates and must withstand a variety of static and dynamic mechanical loading conditions to ensure adequate reliability of the device. Tribological loads are also among these loading conditions, and suitable characterization methods and strategies are required for analyzing friction and wear for a variety of tribological contact situations. In the present work, Mo films were deposited on polyimide substrates by high-power impulse magnetron sputtering and then pre-conditioned by straining to several strain levels, including crack onset strain and strains within the crack saturation regime. Subsequently, ball-on-disk tests against different counterpart materials, namely glass, steel, and polymer, were performed to evaluate different tribological contact situations. The comparison of the results of morphologies and characteristics of the films using surface images for strained and unstrained samples provide insight into how increasing straining of the films and crack formation affect the enhanced fracture of the deposited Mo films, which served as a model system in these investigations.