Band gap engineering in graphene nanoribbons and their heterostructures

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It is now well-established that an electronic band gap which is typical for a semiconductor can emerge in the gap-less 2D material graphene if it is synthesized in the form of nearly-one-dimensional stripes. Such stripes, commonly called graphene nanoribbons, or GNRs, are particularly amenable to controlled manipulation of their electronic band gap, using their width, edge structure and chemical doping as parameters. The goal of this proposal is to perform a basic scientific study of GNRs and GNR-based semiconductor heterojunctions, which are constructed by appropriate selection of precursors from a family of molecules that is derived by systematic structural modification of the well-known cGNR-forming monomer 6,11- dibromo-1,2,3,4-tetraphenyltriphenylene. One objective to achieve this goal is to determine the dependence of the electronic structure of the GNRs on systematic, atomically precise structural and chemical modification. A second objective is to construct heterojunctions by connecting two types of precursor molecules that are known to form GNRs of distinctly different band gap (type 1 semiconductor junction), or by connecting two types of precursor molecules that form GNRs of similar but staggered gap (type 2 semiconductor junction). A third objective is to perform pioneering experiments that seek to connect GNRs, especially those with chemically modified edges, via metalation to form two-dimensional metal-graphenic hybrid structures. The outcomes of this basic scientific project are a set of design rules for band gap engineered GNR heterojunctions based on the selected family of precursor molecules, which might help enable some new and interesting materials for applications, such as carbon-based nano-electronic devices, and optical materials.