Fig. 3.

Surface analysis of the wear track. Raman 2D mapping of the wear track for the characteristic E_2g peak (at ~383 cm⁻¹) of molybdenum disulfide and characteristic G peak (at ~1600 cm⁻¹) of carbon-layered structures after initial 300 cycles (a, c) and 3000 cycles (b, d). Insets demonstrate typical MoS₂ (a, b) and graphitic carbon (c, d) signatures inside the wear track. e Twelve points across the wear track for which LDSPI analysis performed. Increase in intensity for f molecular sulfur S₂ peak at 64 atomic mass units and g molybdenum carbide Mo₂C peaks at 204 atomic mass units indicates transformation of molybdenum and sulfur after disintegration of molybdenum disulfide. The samples were analyzed immediately after the test without cleaning. The scale bars are 50 μm