title: Friction at atomic-scale surface steps: experiment and theory.
abstract: Experiments performed by friction force microscopy at atomic-scale surface steps on graphite, MoS2, and NaCl in ambient conditions are presented. Both step-down and step-up scans exhibit higher frictional forces at the edge, but distinguish in their load dependence: While the additional frictional force due to the step edge increases linearly with load if the tip has to jump a step up, it remains constant for downward jumps. This phenomenon represents a universal effect that can be explained in terms of a modified Prandtl-Tomlinson model featuring a Schwoebel-Ehrlich barrier at steps.
authors.affiliation: Institute for Microstructure Technology, Forschungszentrum Karlsruhe, P.O. Box 3670, 76021 Karlsruhe, Germany. hendrik.hoelscher@imt.fzk.de
authors.forename: Hendrik
authors.initials: H
authors.lastname: Hölscher
authors.forename: Daniel
authors.initials: D
authors.lastname: Ebeling
authors.forename: Udo D
authors.initials: UD
authors.lastname: Schwarz