Temperature and velocity dependent friction of a microscale graphite-DLC heterostructure

One of the promising approaches to achieving large scale superlubricity is the use of junctions between existing ultra-flat surface together with superlubric graphite mesas. Here we studied the frictional properties of microscale graphite mesa sliding on the diamond-like carbon, a commercially available material with a ultra-flat surface. The interface is composed of a single crystalline graphene and a diamond-like carbon surface with roughness less than 1 nm. Using an integrated approach, which includes Argon plasma irradiation of diamond-like carbon surfaces, X-ray photoelectron spectroscopy analysis and Langmuir adsorption modeling, we found that while the velocity dependence of friction follows a thermally activated sliding mechanism, its temperature dependence is due to the desorption of chemical groups upon heating. These observations indicate that the edges have a significant contribution to the friction. Our results highlight potential factors affecting this type of emerging friction junctions and provide a novel approach for tuning their friction properties through ion irradiation.