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Issue 13, 2021
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Selective saturation of step-edges as a tool to control the growth of molecular fibres

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Abstract

The concept of bottom-up self-organisation has become a promising alternative for structuring molecular materials, which are hardly accessible by conventional top-down approaches such as lithography due to their limited chemical robustness. While these materials often tend to form three-dimensional, crystalline islands or fibres upon film growth, the size and orientation of such fibres are mainly governed by appropriate preparation conditions as well as microscopic interactions at the interface with the supporting surface. Substrate surface defects such as vacancies or step-edges, which cannot be completely ruled out on real surfaces on the mesoscopic scale, can act as preferred nucleation sites for molecules that leads to parasitic film growth competing with their intrinsic alignment prevailing on an ideal surface. In the present study, we demonstrate for the case of para-quaterphenyl (p-4P) that the presence of azimuthally disordered, fibres on Ag(111) surfaces can be understood as a superposition of step-mediated nucleation and the intrinsic epitaxial fibre growth on ideal surfaces. We validate the concept by purposely exposing the silver substrates briefly to oxygen or even ambient air to passivate the more reactive step-sites, which hampers subsequently grown molecular films to nucleate at these step-edges. This yields a truly epitaxial alignment as well as an enlargement of the fibres present on the whole sample.

Graphical abstract: Selective saturation of step-edges as a tool to control the growth of molecular fibres

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Article information


Submitted
31 Dec 2020
Accepted
18 Jan 2021
First published
18 Jan 2021

Phys. Chem. Chem. Phys., 2021,23, 8023-8029
Article type
Paper

Selective saturation of step-edges as a tool to control the growth of molecular fibres

M. Dreher and G. Witte, Phys. Chem. Chem. Phys., 2021, 23, 8023
DOI: 10.1039/D0CP06725C

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