Chemical and physical origins of friction on surfaces with atomic steps

Friction results from a set of complex processes that act together to resist relative motion. Despite this complexity, friction is often described using simple phenomenological expressions that relate normal and lateral forces via the friction coefficient. The defined parameter encompasses multiple, sometimes competing effects. To better understand the origins of friction, Zhe Chen and an interdisciplinary team of researchers in the departments of chemical engineering, mechanical engineering and materials research studied a chemically and topographically well-defined interface between silica and graphite using a single-layer graphene step edge setup.