FRICTION FORCE STUDIES ON LAYERED MATERIALS USING AN ATOMIC-FORCE MICROSCOPE

We have studied friction force versus normal load on the nanometer sca le on three layered materials which are expected to exhibit different mechanical properties: 2H-MoS2, 2H-NbSe2, alpha-MoO3. Different behavi ours have been observed, such as plastic deformation and local wear. U nder well-defined conditions there exists an analogy between nanoscopi c experimental results and macroscopic friction results predicted by m odels (Amontons' law for instance). It is then possible to extract mea n values of the friction coefficient on the nanometer scale. We are in terested in friction measurements under atmospheric conditions which c orrespond to real sliding conditions. The influence of parameters such as surface pollution and scan speed appears to be determinant for the reliability of the results. (C) 1997 Elsevier Science B.V.