Dynamics of Interaction of Magnesium Atoms on Methoxy-Terminated Self-Assembled Monolayers: An Example of a Reactive Metal with a Low Sticking Probability

Abstract

The collision of low-flux vapor-generated Mg atoms with a methoxy-terminated self-assembled monolayer (SAM) at room temperature results primarily in nonreactive scattering from the surface. Those atoms that adsorb undergo reaction via O−C bond insertion to form Mg−O−R products, with an estimated activation energy of 38 ± 9 kJ mol-1. These products, in turn, provide nucleation sites for the subsequent formation of Mg clusters. As growth continues, a nonuniform Mg overlayer eventually forms. These behaviors contrast with that of vapor-deposited Al (which shows a high sticking probability and low chemical reactivity under the same experimental conditions). This behavior is consistent with quantum chemical predictions of differences in the ability of the −OCH3 group to stabilize these metal atoms. Overall, these results highlight the importance of dynamic processes in controlling the interfacial chemistry and metal overlayer morphology in vapor-deposited films on organic surfaces.