NANOSCALE INVESTIGATION OF INDENTATION, ADHESION AND FRACTURE OF DIAMOND (111) SURFACES

Molecular dynamics simulations have been used to model the dynamics of indentation and the resulting damage for a (111) surface of a (1x1) hydrogen terminated diamond tip interacting with the (111) surface of both a (1x1) hydrogen terminated diamond crystal and a non-hydrogen terminated diamond crystal. In both cases, indentation can result in a non-adhesive (i.e., elastic) or an adhesive (i.e., plastic) interaction depending on the maximum value of the applied load. Further, adhesion is usually accompanied by fracture and is independent of where the tip contacts the surface. In the case of the hydrogen terminated crystal, the diamond crystal structure is significantly disrupted as a result of the indentation. When the hydrogen is removed from the crystal's surface, adhesion occurs at lower loads than previously observed. However, the crystal structure is not significantly altered as a result of the indentation. The state of the surface dictates the type of indentation mechanism.