Nanoscale Friction of Manganite Superlattice Films Controlled by Layer Thickness and Fluorine Content

Abstract Frictional losses play a major role in global energy consumption, making control of friction across length scales essential for improving efficiency. Since friction at the mesoscale often originates from processes at the nanoscale, understanding and controlling nanoscale friction is key to designing low‐friction, high‐performance materials. Here, nanoscale friction in [LaMnO ₃ ] _m /[SrMnO ₃ ] _n superlattice films using lateral force microscopy is investigated, focusing on the effects of fluorine doping and top‐layer thickness. Across all films, the friction force scales linearly with the sum of the applied normal load and adhesion force. While absolute friction forces vary locally due to adhesion variations, the friction coefficient remains consistent for each film but is systematically influenced by fluorine concentration and top‐layer thickness. The thickness dependence indicates that frictional energy dissipation extends up to ≈5 nm below the surface, underscoring the role of subsurface structure. This dissipation is attributed to viscoelastic losses in the stress field and evanescent waves generated by the sliding tip, which quantitatively explain the observed friction coefficients. These results demonstrate that, once adhesion is accounted for, the friction coefficient is a reproducible material property that can be systematically tuned—offering a general strategy for tailoring frictional behavior through controlled surface and subsurface modifications.