Molecular Dynamics Study of the Formation of a Self-Assembled Monolayer on Gold

Molecular dynamics simulations have been used to study the formation of nanoscale islands of self-assembled monolayers (SAMs) starting from alkanethiol molecules initially lying down in a disordered physisorbed layer on gold. These islands form when tens of alkane thiols stand up together within tens of ns after chemisorption begins. The alkane chains in these islands are found to be tilted, and the tilt direction precesses around the center of the island. This precession, together with the packing of the sulfur atoms, signals the formation of a SAM island, occurring prior to the tilting and orientation ordering of the chains.