Boron Nitride Nanomesh as a Scaffold for Functional Surfaces, Nanocatalysts and Molecular Electronics

In the recent past substantial efforts have been devoted to define mechanisms that lead to self-assembly of regular nanostructures at surfaces, including the exploitation of regular arrays of misfit dislocations, long-range adsorbate-adsorbate interactions mediated by metallic surface states, or short-range adsorbate-adsorbate interactions based on hydrogen bonds. Very recently, a new type of self-assembly mechanism has been found in a purely inorganic system. It leads to a surprising new nanostructured material based on a bilayer of hexagonal boron nitride (h-BN) on a Rh(111) surface [M. Corso et al., Science 303, 217 (2004)]. A highly regular mesh forms by self-assembly, with a 3.2 nm periodicity and a 2 nm hole size. Two layers of mesh cover the surface uniformly after high-temperature exposure of the clean rhodium surface to borazine (HBNH)3. The two layers are offset in such a way as to expose a minimum metal surface area. Hole formation is likely driven by the lattice mismatch of the film and the rhodium substrate. This regular nanostructure has remarkable properties and can serve as a template to organize molecules, as is exemplified by the decoration of the mesh by C60 molecules.
The main objectives of the NanoMesh project are to understand the self-assembly processes leading to this highly interesting and non-trivial nanostructure, to find routes for controlling the mesh parameters and for mass production, and to demonstrate its prospects for future applications as a sturdy oxygen- and carbon-free template for the production of nanocatalysts, nanomagnets and functionalized surfaces. Rather than taking a broad approach on self-assembly in general, the NanoMeshproject thus focuses on this particular h-BN material. The NanoMesh project brings together leading specialists in Europe with unique expertise in synthetic chemistry as well as novel experimental and theoretical techniques to investigate the processes leading to the selfassembly of the nanomesh in situ, and to explore new combinations of chemical precursors and substrates in order to control the mesh size and shape. It also includes the expertise for fabricating self-assembling hydrogen-bonded molecular networks in order to try to achieve higher hierarchies of self-assembly on top of the nanomesh, leading to regular structures that bridge the nanoscopic and the mesoscopic scale, and to demonstrate the design of functionalized surfaces for sensing and biological applications. An industrial partner will investigate the nanomeshes as potential substrates for electronic devices, specifically for spintronic and quantum computing applications. The results will enable the application specific tailoring of regular nanostructures and the prediction of their physical, chemical and maybe also biological properties.