Model experiments of superlubricity of graphite

Graphite is known to be a good solid lubricant. The low-friction behavior is traditionally ascribed to the low resistance to shear. We have recently observed that the ultra-low friction found in friction force microscopy experiments on graphite is due to a effect called superlubricity [M. Dienwiebel, G. S. Verhoeven, N. Pradeep, J.W.M. Frenken, J.A. Heimberg, H.W. Zandbergen, Phys. Rev. Lett. 92 (2004) 126101]. Here, we provide additional experimental evidence that superlubricity has been taken place between a small graphite flake attached to the scanning tip and the graphite surface. Finally, we speculate about the significance of this for the lubricating properties of graphite. (C) 2004 Elsevier B.V. All rights reserved.