Figure 3
AFM images of three MoS 2 nanotubes. There is low interaction strength between the nanotubes and underlying HOPG substrate and the corresponding values of COF with marked areas of the friction measurements; scale bars = 500 nm. (a) A kink of the tube, 200 nm in diameter (trace image), COF (0.018 ± 0.004); (b) the nanotube, 14 nm in diameter, laid over surface steps, COF (0.022 ± 0.005); (c) partially detached nanotube, 110 nm in diameter, with the line profile A (inset), COF (0.033 ± 0.001); and (d) the same nanotubes put into contact with substrate with the line profile B (inset), COF (0.057 ± 0.01).