Nanoindentation Response of Self-Assembled Monolayers on Gold with Conical Carbon Indenters

Nanoindentation characteristics of 1-hexadecanethiol self-assembled monolayers (SAMs) on an Au surface are studied using molecular dynamics (MD) simulation. The effects of different conical angles of indenter and indentation depths on the mechanical properties of the SAMs are simulated. The interaction of SAM atoms is described by a general universal force field (UFF), the second-moment approximation for tight-binding (TB-SMA) is used for Au substrate, and Lennard-Jones potential function is employed to describe interaction among the indenter, the SAMs, and the Au substrate atoms. The simulation results show that the adhesion force and relaxation force increase with increasing the indentation depth and conical angle of the indenter. In addition, the plastic energy of the SAMs is an order larger than the elastic energy.