Scratching the Surface: Fundamental Investigations of Tribology with Atomic Force Microscopy.

Abstract

A few years after the invention of the scanning tunneling microscope (STM), the atomic force microscope (AFM) was developed. Instead of measuring tunneling current, a new physical quantity could be investigated with atomic-scale resolution: the force between a small tip and a chosen sample surface. This paper reviews progress and recent results obtained with AFM and other closely related techniques in the field of nanotribology, and attempts to point out many of the unresolved questions that remain. The goal of this paper is to demonstrate that AFM is capable of producing atomic-scale knowledge. As such, the authors will focus upon some of the contributions of the AFM to nanotribology. They will almost exclusively discuss results that shed light on the actual atomic and molecular processes taking place, as opposed to the more applied investigations of microscale properties which are also carried out with AFM. They will accompany this discussion by mentioning related theoretical efforts and simulations, although their main emphasis will be upon experimental results and the techniques used to obtain them, as well as suggested future directions. In many ways, AFM techniques for quantitative, fundamental nanotribology are only in a nascent stage; certain key issues such as force calibration,more » tip characterization, and the effects of the experimental environment, are not fully resolved or standardized. The authors thus begin with a critical discussion of the relevant technical aspects with using AFM for nanotribology. 289 refs.« less