Force microscopy is a versatile instrument to investigate physical phenomena on surfaces. The first emphasis is on the study of friction on the nanometer-scale, also called nanotribology. It will be shown that atomic-scale stick-slip is relatively well understood, where the dependence on velocity and normal force is experimentally investigated and interpreted in terms of an extended Tomlinson model. It is essential to include thermal actuation to understand the observed phenomena. The transition from atomic-scale stick slip to continuous sliding will be described [1]. The detailed analysis yields the energy corrugation and the lateral contact stiffness as a function of load. It is found that continuum mechanics is not anymore valid at these dimensions. Recently, it has been shown that atomic friction can be controlled with rather high accuracy by electrostatic actuation [2]. It will be shown that this type of actuation leads to variations of the energy barriers, which makes it possible to enter the regime of superlubricity. Recent experiments on hetero-structures of KBr on NaCl have shown that the energy barriers can also vary in space, which leads to transition from regions with atomic stick slip to regions with smooth sliding [3].

[1] A. Socoliuc, R. Bennewitz, E. Gnecco and E. Meyer, Transition from Stick-Slip to Continuous Sliding in Atomic Friction: Entering a New Regime of Ultra-low Friction, Phys. Rev. Lett. 92, 134301-1 (2004).

[3] S. Maier et al., to be submitted (2007).

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