Adsorption geometry and electronic properties of flat-lying monolayers of tetracene on the Ag(111) surface

TL;DR

This study uses DFT calculations to analyze the adsorption geometry and electronic properties of tetracene monolayers on Ag(111), revealing stable adsorption sites, the role of dispersive interactions, and the behavior of interface states.

Contribution

It provides a systematic DFT analysis of tetracene monolayers on Ag(111), identifying stable adsorption sites and elucidating electronic state behaviors with respect to substrate lattice constants.

Findings

Bridge and hollow sites are most stable for adsorption.

Binding energy is dominated by dispersive interactions.

Interface state position depends on substrate lattice constant.

Abstract

The geometrical and electronic properties of the monolayer (ML) of tetracene (Tc) molecules on Ag(111) are systematically investigated by means of DFT calculations with the use of localized basis set. The bridge and hollow adsorption positions of the molecule in the commensurate $\gamma$-Tc/Ag(111) are revealed to be the most stable and equally favorable irrespective to the approximation chosen for the exchange-correlation functional. The binding energy is entirely determined by the long-range dispersive interaction. The former lowest unoccupied orbital remains being unoccupied in the case of $\gamma$-Tc/Ag(111) as well as in the $\alpha$-phase with increased coverage. The unit cell of the $\alpha$-phase with point-on-line registry was adapted for calculations based on the available experimental data and the computed structures of the $\gamma$-phase. The calculated position of the Tc/Ag(111) interface state is found to be noticeably dependent on the lattice constant of the substrate, however its energy shift with respect to the Shockley surface state of the unperturbed clean side of the slab is sensitive only to the adsorption distance and in good agreement with the experimentally measured energy shift.