Molecular Simulation of Contact/Separation Behavior of Platinum Surfaces with Adsorbed Acetylenes

CH Li and FL Duan, TRIBOLOGY LETTERS, 72, 116 (2024).

DOI: 10.1007/s11249-024-01917-6

Ambient hydrocarbons adsorbed on the contact surface of nanoelectromechanical (NEM) switches would impact its performance. In this study, we utilized reactive molecular dynamics simulations to investigate the cyclic contact/separation process of Pt(111)/C2H2/Pt(111) systems. Our results demonstrate that substrate damage decreases as acetylene coverage increases from sub-monolayer to multilayer. This suppression occurs due to the presence of acetylene molecules, which can suppress direct (Pt-Pt connection) and indirect (Pt-(Cx)-Pt-like connection) interfacial bonding between the two substrates, depending on their coverage. Moreover, we observed the formation of chain-like oligomers after multiple contact/separation simulations in the monolayer model, much more significantly compared with the sub-monolayer and multilayer models. These oligomers arise from polymerization reactions among fragmented acetylene molecules, primarily formed through acetylene dehydrogenation. In the sub-monolayer model, numerous transferred Pt atoms at the interface hinder bonding between acetylene fragments, whereas in the multilayer model, only a few acetylene fragments form during the contact process, due to the well- organized and dense acetylene layer adsorbed on the substrate surfaces. These insights shed light on the atomic-scale mechanisms underlying substrate damage and chain-like oligomers formation in metal NEM switches.

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