Simulating the nanomechanical response of cyclooctatetraene molecules on a graphene device

TL;DR

This study uses first-principles calculations to explore how external gate voltage influences the shape, orientation, and mobility of cyclooctatetraene molecules on graphene, revealing controllable nanomechanical responses.

Contribution

It provides a detailed analysis of how carrier density modulates molecular conformation and diffusion on graphene, introducing a method to control molecular behavior via gating.

Findings

Increased hole doping flattens COT molecules and reduces diffusion barriers.

Electron doping causes an abrupt transition to planar conformation at a specific carrier density.

Molecular shape and mobility can be externally controlled by gating graphene devices.

Abstract

We investigate the atomic and electronic structures of cyclooctatetraene (COT) molecules on graphene and analyze their dependence on external gate voltage using first-principles calculations. The external gate voltage is simulated by adding or removing electrons using density functional theory (DFT) calculations. This allows us to investigate how changes in carrier density modify the molecular shape, orientation, adsorption site, diffusion barrier, and diffusion path. For increased hole doping COT molecules gradually change their shape to a more flattened conformation and the distance between the molecules and graphene increases while the diffusion barrier drastically decreases. For increased electron doping an abrupt transition to a planar conformation at a carrier density of -8$\times$10$^{13}$ e/cm$^2$ is observed. These calculations imply that the shape and mobility of adsorbed COT molecules can be controlled by externally gating graphene devices.