Friction Dissymmetry on Hexagonal Boron Carbon Nitride

The classical friction law posits that macroscopic friction is directly proportional to the normal force, represented by a constant friction coefficient. However, frictional behavior becomes increasingly complex at the nanoscale. We reveal a counterintuitive instance of dissymmetric friction during the sliding of a graphene flake on a hexagonal boron carbon nitride (<i>h</i>-BCN) substrate. This dissymmetry is marked by significantly different friction coefficients in opposing directions along the same sliding path. We attribute this unexpected behavior to the dissymmetric potential energy landscape of <i>h</i>-BCN, which fundamentally differs from the symmetrical profiles seen in graphene and <i>h</i>-BN, despite <i>h</i>-BCN being perceived as a composite of these materials. Our findings enhance the understanding of nanoscale friction and pave the way for the development of innovative nanodevices that utilize directional friction control.