Tribological investigations of Mo films deposited on thin polyimide substrates

In flexible and/or wearable electronics the thin films deposited on compliant substrates are not only subjected to straining and bending but also to tribological loading conditions. A frequently used method to assess tribological properties of materials systems is the ball-on-disc test. In the current work, Mo films were deposited by high power impulse magnetron sputtering on polyimide substrates to serve as a model system. To establish different tribological contact conditions, a series of different counterpart materials was chosen for the performed ball-on-disc tests. A detailed analysis by 3D confocal laser scanning microscopy and scanning electron microscopy revealed details about the wear mechanisms active during sliding where mainly abrasion of the softer one of the material pair was noticed. The obtained results for friction and wear together with the performed simulations of the induced stresses due to the loading conditions show that ball-on-disc tests can contribute to the understanding of the tribological response of metallic films on compliant substrates which in turn may help to improve the lifetime of components in flexible and/or wearable electronic applications.