Energy Shift and Wavefunction Overlap of Metal-Organic Interface-States

TL;DR

This study investigates the properties of metal-organic interface states using experiments and theory, revealing how molecular distance, density, and bending influence their energy and wavefunction overlap.

Contribution

It combines time-resolved photoemission and density functional theory to elucidate the formation and modulation of interface states on metal-organic interfaces.

Findings

Interface state energy depends on molecular-metal distance.

Bending carboxyl groups increases wavefunction overlap.

Formation mechanism from surface states is identified.

Abstract

The properties of Shockley-type interface states between $\pi$-conjugated organic molecular layers and metal surfaces are investigated by time-resolved two-photon photoemission experiments and density functional theory. For perylene- and naphthalene-tetracarboxylic acid dianhydride (PTCDA and NTCDA) adsorbed on Ag(111), a common mechanism of formation of the interface state from the partly occupied surface state of the bare Ag(111) is revealed. The energy position is found to be strongly dependent on the distance of the molecular carbon rings from the metal and their surface density. Bending of the carboxyl groups enhances the molecular overlap of the interface state.