Tailoring molecular island shapes: influence of microscopic interaction on mesostructure

Simon Aeschlimann,Angelika Kühnle,Martin Aeschlimann,Lu Lyu,Benjamin Stadtmüller

doi:10.1007/s12274-020-2705-0

Abstract

Controlling the structure formation of molecules on surfaces is fundamental for creating molecular nanostructures with tailored properties and functionalities and relies on tuning the subtle balance between intermolecular and molecule-surface interactions. So far, however, reliable rules of design are largely lacking, preventing the controlled fabrication of self-assembled functional structures on surfaces. In addition, while so far many studies focused on varying the molecular building blocks, the impact of systematically adjusting the underlying substrate has been less frequently addressed. Here, we elucidate the potential of tailoring the mesoscopic island shape by tuning the interactions at the molecular level. As a model system, we have selected the molecule dimolybdenum tetraacetate on three prototypical surfaces, Cu(111), Au(111) and CaF2(111). While providing the same hexagonal geometry, compared to Cu(111), the lattice constants of Au(111) and CaF2(111) differ by a factor of 1.1 and 1.5, respectively. Our high-resolution scanning probe microscopy images reveal molecular-level information on the resulting islands and elucidate the molecular-level design principles for the observed mesoscopic island shapes. Our study demonstrates the capability to tailor the mesoscopic island shape by exclusively tuning the substrate lattice constant, in spite of the very different electronic structure of the substrates involved. This work provides insights for developing general design strategies for controlling molecular mesostructures on surfaces.

Highlights

One of the crucial challenges in the miniaturization of device structures for further information technology and photonic applications is to devise novel concepts to fabricate active functional units on surfaces with atomic or molecular precision at the nanoscale
The mesh phase, which is formed by flat-lying molecules, is not considered any further, because in this work we will focus on the chain phase solely, which is composed of upright-standing molecules
A strategy is presented for tuning the mesoscopic island shape by rationally changing the underlying substrates’ lattice constant

Summary

Introduction

One of the crucial challenges in the miniaturization of device structures for further information technology and photonic applications is to devise novel concepts to fabricate active functional units on surfaces with atomic or molecular precision at the nanoscale In this context, molecular self-assembly processes on surfaces have emerged as a powerful tool for creating functional molecular nanostructures on surfaces [1,2,3,4,5,6]. The focus of intense research has been on exploring the variability of the molecular building blocks [24], while the influence of systematically varying the underlying substrate is rarely addressed This is unfortunate as the substrate can act as a template [40, 41], directing molecular structure formation and providing a further dimension in rationally controlling molecular self-assembly on surfaces [42]. We focus on this aspect and show that the mesoscopic shape of self-assembled molecular islands can be controlled by tuning the involved interactions

Methods

Results

Discussion

Conclusion