| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Friday Sessions |
| Session TF-FrM |
| Session: | Self-assembled Monolayers and Organic/Inorganic Interface Engineering |
| Presenter: | Peter Beton, The University of Nottingham, UK |
| Authors: | V.V. Korolkov, The University of Nottingham, UK M. Baldoni, The University of Nottingham, UK K. Watanabe, National Institute for Materials Science, Japan T. Taniguchi, National Institute for Materials Science, Japan E. Besley, The University of Nottingham, UK P.H. Beton, The University of Nottingham, UK |
| Correspondent: | Click to Email |
The formation of two-dimensional supramolecular arrays provides a highly flexible route to the control of the spatial organization, down to the molecular scale, of the chemical functionality of a surface. These molecular networks, which can be formed through self-assembly processes on a variety of different substrates including semiconductors, metals, insulators0 and layered materials, are, in almost all cases, limited to monolayer thickness. Progress towards the growth of higher layers has so far been much more limited, with demonstrations of bilayer growth and site-specific molecular adsorption. Specifically, the additional functional control, which may be achieved through the formation of heterostructures realized by placing one supramolecular layer on another and resulting in growth into the third dimension perpendicular to the substrate, has not been widely explored for these materials. Such additional control of material properties is well established for semiconductors, both organic and inorganic, and, more recently, layered materials, providing a strong motivation to explore analogue materials derived from stacked supramolecular networks. Here we describe the successful formation of heterostructures formed by the sequential growth of distinct one- and two-dimensional arrays. It is possible, using high resolution atomic force microscopy (AFM) to determine an epitaxial alignment between successive layers. Furthermore, we demonstrate using classical molecular dynamics (MD) simulations that the placement and dimensions of the layers may be robustly predicted using well established force-fields.
Supramolecular heterostructures1 are formed by growing sequential layers of bi- and mono-component two-dimensional molecular arrays stabilized by hydrogen bonding. The heterostructures are formed on hexagonal boron nitride by depositing cyanuric acid/melamine (CA.M) followed by terephthalic acid (TPA) or trimesic acid (TMA) and imaged using atomic force microscopy under ambient conditions with resolution approaching 0.1 nm. A clear epitaxial arrangement is observed between these layers having intrinsically distinct symmetries and lattice constants, which for TMA/CA.M corresponds to a (√3 x √3)R30o phase, while TPA forms rows with a molecular separation that matches the CA.M period. Structures calculated using classical molecular dynamics are in excellent agreement with the orientation, registry and dimensions of the epitaxial layers. Calculations confirm that van der Waals interactions provide the dominant contribution to the adsorption energy and registry of the layers.
1 Korolkov et al., Nat. Chem., 2017, in press.