Abstract
We sputter-deposited oxide thin films such as Y2O3, SiO2, TiO2, Ta2O5, CeO2, and MoO3 and studied water droplet wettability and the surface friction coefficient under the controlled conditions of 20-25°C and 50-60% RH. Water droplet wettability was evaluated by measuring the contact angle. We found that the angle increased and saturated over time for all tested oxide thin films and that contact angle saturation depended on the type of oxide thin films used. The relationship between the contact angle and r/Z (ion radius divided by cation charge) suggests that the oxide surface structure affects adsorption states. We also found that the thin film surface friction coefficient also decreased over time in line with variations in the contact angle. The correspondence between the friction coefficient and adhesion derived from the contact angle means that friction originates in adhesive force.
