Work-function modification of au and ag surfaces upon deposition of self-assembled monolayers: Influence of the choice of the theoretical approach and the thiol decomposition scheme

We have characterized theoretically the work-function modifications of the (111) surfaces of gold and silver upon deposition of self-assembled monolayers based on methanethiol and trifluoromethanethiol. A comparative analysis is made between the experimental results and those obtained from two widely used approaches based on density functional theory. The contributions to the total work-function modifications are estimated on the basis of two decomposition schemes of the thiol molecules that have been proposed in the literature. The contributions are found to differ significantly between the two approaches, as do the corresponding adsorption energies. Radical versus molecule: Modification of the Ag and Au work function upon deposition of self-assembled monolayers based on CH₃SH and CF₃SH is characterized theoretically. A comparative analysis is made between the experimental results and those obtained from two DFT approaches. The contribution of the molecular and interfacial parts to the work function is assessed on the basis of two known decomposition schemes of the thiolated molecule.