Reduction of friction at very low normal loads and for very small contact areas is important for the development of micro devices. High performance hard coatings such as diamond-like carbon (DLC) films and improved surfaces with nanostructures are being investigated with respect to their friction reduction properties. Previously, difficulties associated with the production of nano-scale periodic structures in DLC films have prohibited the study of such films.
In the present study, the friction properties of the DLC film with periodic structures were investigated at the nano-scale using an atomic force microscope (AFM). These periodic structures were generated on the surface of the DLC film by means of a femtosecond (fs) laser having the fluence near the ablation threshold. Friction tests were carried out under normal loads ranging from 20 nN to 130 nN, and the frictional directions were 0º, 45º and 90º (relative to the line along which the periodic structures were created). The lateral force of the DLC film with the periodic structures was lower than that of the film without the periodic structures. We have concluded that decreases in adhesive forces produce significant decreases in lateral forces for the same normal loads.