Mechanical response of diamond at nanometer scales: diamond polishing and atomic force microscopy

摘要

Total energy pseudopotential methods are used to study two different processes involving the mechanical interaction of diamond nanoasperities and diamond surfaces: the wear processes responsible for diamond polishing, and the mechanical deformation of tip and surface during the operation of the Atomic Force Microscope in contact mode (CM-AFM). The strong asymmetry in the rate of polishing between different directions on the diamond (110) surface is explained in terms of an atomistic mechanism for nano-groove formation. The post-polishing surface morphology and the nature of the polishing residue predicted by this mechanism are consistent with experimental evidence. In the case of CM-AFM, our calculations show that a tip terminated in a single atom is able to sustain forces in excess of 30 nN. The magnitude of the normal force was unexpectedly found to be very similar for the approach on top of an atom or on a hollow position on the surface. This behaviour is due to tip relaxations induced by the interaction with the surface. These forces are also rather insensitive to the chemical nature of the tip apex.