Surface state engineering of molecule-molecule interactions

TL;DR

This paper explores how manipulating electronic structures at interfaces can control molecule-molecule interactions, enabling precise self-assembly in organic devices by tuning charge transfer and surface dipoles.

Contribution

It demonstrates the interplay of energy level alignment, charge transfer, and surface dipoles in controlling molecular forces on metal surfaces, advancing interface engineering techniques.

Findings

Charge transfer influences molecular forces significantly.

Energy level alignment governs self-assembly behavior.

Surface dipoles modulate molecule interactions.

Abstract

Engineering the electronic structure of organics through interface manipulation, particularly the interface dipole and the barriers to charge carrier injection, is of essential importance to improved organic devices. This requires the meticulous fabrication of desired organic structures by precisely controlling the interactions between molecules. The well-known principles of organic coordination chemistry cannot be applied without proper consideration of extra molecular hybridization, charge transer and dipole formation at the interfaces. Here we identify the interplay between energy level alignment, charge transfer, surface dipole and charge pillow effect and show how these effects collectively determine the net force between adsorbed porphyrin 2H-TPP on Cu(111). We show that the forces between supported porphyrins can be altered by controlling the amount of charge transferred across the interface accurately through the relative alignment of molecular electronic levels with respect to the Shockley surface state of the metal substrate, and hence govern the self-assembly of the molecules.