Damage Behavior Between Two Pt(111) Surfaces with Adsorbed Benzene Molecules

Hydrocarbon adsorption at the contact interface of nano-electromechanical switches is the main cause of device failure. This study simulated the approaching and separation process between two Pt(111) surfaces with adsorbed benzene molecules by Reactive molecular dynamics (ReaxFF-MD) simulations, to investigate the influence of benzene molecular coverage and relative orientation of substrate crystal surfaces on the adsorption structure of interfacial benzene molecules and substrate surface damage. During the approaching process, the interfacial benzene molecules form horizontal top and hollow adsorption structures in the sub-monolayer and monolayer coverage models, yet tilted adsorption structures in the multilayer coverage model. The formation of top and hollow adsorption structures is significantly affected by the relative crystallographic orientation. When two substrate surface atoms are aligned with each other, the interfacial benzene molecule is easy to form top adsorption structure, otherwise it tends to form hollow adsorption structure. However, the formation of the tilted adsorption structure is independent of the relative crystallographic orientation. Benzene molecules in horizontal hollow adsorption are usually bonded with two surfaces simultaneously. During the separation process, these bridging benzene molecules, simultaneously bonded with two substrates, lead to atomic detachment and other forms of damage on the metal surface. This feature may cause much more substrate damage in the monolayer coverage model than in the other two coverage models. This work provides a deeper insight into the damage mechanism of the contact surface of nano-electromechanical devices.