Fig. 1: Wear tests of the graphite/graphite contact.

a, b Experimental setup (a) and optical microscopy (OM) image (b) of the graphite/graphite contact in the mesa/substrate setup. c Experimental measurement of the average shear stress below the breakdown pressure. The results include both loading and unloading processes. The error bar represents the standard deviation of 10 repeated experiments, and k is the fitting slope. d, e OM (d) and atomic force microscopy (AFM, e) images of the graphite substrate after sliding tests. The testing procedure includes 2 steps of (1) pre-cleaning the substrate within a region of 26 μm × 14 μm (the large dashed box), and (2) conducting sliding tests at the center of the cleaned region under the pressure of 9.45 GPa with a reciprocating sliding amplitude of 10 μm and a sliding velocity of 10 μm/s (the small dashed box). The sliding distance reached 10 mm in 5 × 10² cycles. f Raman characterization of the graphite substrate at the marked points. g–i Band contrast (BC, g) and inverse pole figures (IPFs, h, i) of HOPG. j–l BC (j) and IPFs (k, l) of normal flake graphite. Source data are provided as a Source Data file.