Revealing the Buried Metal-Organic Interface: Restructuring of the First Layer by van der Waals Forces

TL;DR

This study uses cryogenic scanning tunneling microscopy to reveal how van der Waals forces from additional layers cause restructuring of the first organic monolayer on Cu(110), affecting buried interfaces.

Contribution

It demonstrates that van der Waals forces from subsequent layers can induce significant restructuring of the first organic monolayer at buried interfaces, a novel insight.

Findings

First-layer molecules are restructured by van der Waals pressure.

Additional molecules are incorporated into the monolayer, adopting an edge-on configuration.

External stress from van der Waals forces influences chemisorbed organic layers.

Abstract

Using molecular manipulation in a cryogenic scanning tunneling microscope, the structure and rearrangement of sexiphenyl molecules at the buried interface of the organic film with the Cu(110) substrate surface have been revealed. It is shown that a reconstruction of the first monolayer of flat lying molecules occurs due to the van der Waals pressure from subsequent layers. In this rearrangement, additional sexiphenyl molecules are forced into the established complete monolayer and adopt an edge-on configuration. Incorporation of second layer molecules into the first layer is also demonstrated by purposely pushing sexiphenyl molecules with the STM tip. The results indicate that even chemisorbed organic layers at interfaces can be significantly influenced by external stress from van der Waals forces of subsequent layers.