This work investigates the friction between polydimethylsiloxane (PDMS) and silicon oxide (SiO_x) in single asperity sliding contact by atomic force microscopy (AFM). Two friction dependences on the normal force are identified: a tensile regime and a compressive regime of normal forces. In the compressive regime, friction is governed by the shear deformation and rupture of junctions between PDMS and SiO_x. In this case, the shear strength τ ≈ 10 MPa is comparable with the cohesive strength of PDMS under compressive loading. In contrast, friction in the tensile regime is also affected by the elongation of the junctions. The single SiO_x-asperity follows a stick–slip motion on PDMS in both normal force regimes. Statistical analysis of stick–slip as a function of the normal force allows determining the necessary amount of energy to break a SiO_x/PDMS junction. Friction between a SiO_x-asperity and a PDMS surface can be rationalized based on an energy criterion for the deformation and slippage of nanometer-scale junctions.

We have investigated the sliding friction behavior of metallic couples with different enthalpy of mixing or reaction by friction force microscopy. Comparing the friction behavior of miscible and immiscible couples we find that in the first case friction is governed by adhesion while the shear strength is low (τ = 3–6 MPa). In the latter case of immiscible couples, adhesion is found to be low and the shear strength is large (τ ≈ 70 MPa). Statistical analysis of atomic stick-slip images recorded on an Au(111) surface with tips of different affinities with gold allows for a deeper understanding of our results. The periodicity of atomic stick-slip images corresponds to the interatomic distance of gold for immiscible counter-bodies. In contrast, for a reactive couple the periodicity of atomic stick-slip significantly differs from the gold interatomic distance and may correspond to the structural length of an ordered intermediate phase at the tip-surface interface.

Thermally grown surface oxide layers dominate the single-asperity tribological behavior of a Zr₆₀Cu₃₀Al₁₀ glass. Increase in oxidation time leads to an increased contribution of shearing and a corresponding decreased contribution of ploughing to friction. This change in the dominating friction and wear mechanism results in an overall minor decrease of the friction coefficient of oxidized surfaces compared to the metallic glass sample with native surface oxide. Our results demonstrate the importance of creating a stable oxide layer for practical applications of metallic glasses in micro-devices involving sliding contact.