Ab initio study of origin and properties of a metal-organic interface state of the PTCDA/Ag(111) system

TL;DR

This study uses density functional theory to analyze the origin and properties of an interface state in the PTCDA/Ag(111) system, revealing how adsorbate interaction transforms a surface state into an unoccupied interface state.

Contribution

It provides a detailed ab initio analysis of the interface state formation in PTCDA/Ag(111), linking theoretical results with experimental observations.

Findings

One of two Ag(111) surface states becomes an unoccupied interface state due to PTCDA adsorption.

The interface state is related to experimentally observed unoccupied states.

The state transformation depends on the substrate thickness.

Abstract

We present a detailed study of a monolayer film of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on Ag(111) (the PTCDA/Ag(111) system). The study is done within density functional theory with the use of the periodic slab model. The slab is chosen to contain a PTCDA monolayer film on a silver thin film of different thicknesses (6, 9, and 12 layers) with the (111) orientation. We show that one of two surface states of the pure Ag(111) films transforms into an unoccupied interface state due to the adsorbate-substrate interaction. The relation of the resulting state to the unoccupied state that has been experimentally observed in the PTCDA/Ag(111) system by scanning tunneling and two photon photoemission spectroscopy is discussed.