Evaluation of atomic-scale wear by an atomic force microscope with a conductive tip

A carbon film deposited by electron cyclotron resonance plasma sputtering is scanning-scratched by an atomic force microscope with a conductive diamond tip by contact pressure smaller than 26GPa and contact resistance between the tip and the scratched surface is evaluated. Fractional change in resistance, which is defined as the ratio of the increase in the contact resistance by the scanning-scratching to the contact resistance on unscratched surface, increases with increase in scratching load and number of scanning-scratching and decreases with increasing scratching velocity, although wear depth is almost constant (0.2-0.4nm). It also increases with increase in environmental humidity above 50 or 60%RH. The mechanism of such changes of the fractional change in resistance is discussed by taking tribachemical oxidation and disordering of crystal structure of the scratched surface into consideration.