Friction Scaling at the Interface of 2D van der Waals Heterostructures

Much of tribology research in the past has been hindered by the fact that friction measurements are overwhelmingly dominated by surface roughness, where a significant experimental limitation has been designing experiments with a well-controlled interface. Two-dimensional (2D) heterostructures present a fantastic new avenue in this regard. Atomically ordered and pristine interfaces can be realized over micron length scales, providing unprecedented opportunity to mix and match material properties, without being limited by issues inherent to the growth process of conventional semiconductor heterostructures, such as interfacial chemistry and lattice matching. To date, the interfacial interactions of these new structures remains relatively poorly understood. Here we investigate the area and temperature scaling of friction as a function of angle between two atomically flat 2D materials with different lattice constants, graphite and h-BN, using atomic force microscopy. We show both the area and temperature scaling of friction varies with the angle of relative alignment, with a stronger dependence close to alignment, suggesting a relationship between the friction force and the presence of a moiré superlattice.