How to restore superlow friction of DLC: The healing effect of hydrogen gas

Among diamond-like carbon coatings, hydrogenated amorphous carbon films have the characteristic of exhibiting superlow friction under ultra-high vacuum. However, most of the films reach this superlow friction regime only for a very short duration. The role of hydrogen on such phenomena is paramount. This paper focuses on the loss of superlow friction and on its restoration through the introduction of hydrogen gas in the friction (or sliding) environment. "Triboscopy", which is a special way of plotting friction data, enabled the understanding of the degradation of the friction coefficient and the healing mechanisms by hydrogen. © 2004 Elsevier Ltd. All rights reserved.