Imaging friction tracks on diamond surfaces using reflection electron microscopy (REM)

Abstract

Reflection electron microscopy (REM) has been applied to image the surface structures of polished natural diamond (001) faces before and after frictional sliding. Friction tracks produced by a diamond stylus sliding at a nominal contact pressure of a few GPa can be clearly seen in REM images of the surface. The contact between the stylus and the surface is shown to be non-uniform. At low nominal contact pressures, ∼3·5 GPa, the surface shows relative dark contrast at the contact areas, which it is suggested is due to structural modification of the top atomic layers. At nominal contact pressures of ∼13 GPa, the surface is damaged on a scale less than the height of polishing lines. At high nominal contact pressures, ∼21 GPa, ‘grooves’ are produced on the surface. This result, and the absence of surface cracking, suggested that plastic deformation is involved in the process of frictional sliding on diamond at high contact pressures.