Fig. 2: Tribological tests between graphite flakes and nanostructured silicon surface.

a Measured friction force during 5120 continuous sliding cycles with a displacement amplitude of \(1\,{{{{{\rm{\mu }}}}}}{{{{{\rm{m}}}}}}\) and speed of \(2\,{{{{{\rm{\mu }}}}}}{{{{{\rm{m}}}}}}/{{{{{\rm{s}}}}}}\) under a normal force of \(14.65\,{{{{{\rm{\mu }}}}}}{{{{{\rm{N}}}}}}\). b and c are the topography of the nanostructured surface before and after 5120 sliding cycles, respectively, where the yellow dashed frame is the boundary of the sliding region. d Measured friction force of graphite flake/nanostructured silicon interface in situ under different normal load with a displacement amplitude of \(1\,{{{{{\rm{\mu }}}}}}{{{{{\rm{m}}}}}}\) and speed of \(2\,{{{{{\rm{\mu }}}}}}{{{{{\rm{m}}}}}}/{{{{{\rm{s}}}}}}\); each point and error bar were obtained by 10 tests and had friction coefficients of 0.00045\(\pm\)0.00025. e–h The Raman characterization results of the sliding region on nanostructured silicon, where e is the optical observation, the red frame is the scan area of \(6\,{{{{{\rm{\mu }}}}}}{{{{{\rm{m}}}}}}\times 6\,{{{{{\rm{\mu }}}}}}{{{{{\rm{m}}}}}}\) (including the whole sliding region), f–h The intensity distributions of D peak (1350 \({{{{{\rm{c}}}}}}{{{{{{\rm{m}}}}}}}^{-1}\)), G peak (1580 \({{{{{\rm{c}}}}}}{{{{{{\rm{m}}}}}}}^{-1}\)) and 2D peak (2700 \({{{{{\rm{c}}}}}}{{{{{{\rm{m}}}}}}}^{-1}\)), respectively, there is no observable graphite composition. i Single-point Raman spectrum at the blue cross mark position in e, the illustration is an enlarged view of the black dash frame region, there are no observable D, G and 2D graphite peaks. j Raman characterization of the bottom surface of graphite flake after 5120 sliding cycles; points 1–9 represent the test positions, there is no observable D peak, and the illustration is the optical observation of flipped graphite flake. Source data are provided as a Source Data file.