Atomically precise construction of uniform single-molecule junctions for molecular electronics

Atomically precise construction of ultra-small electronic devices meets the urgent need for further device miniaturisation and enables numerous electronic applications. In particular, single-molecule junctions are attractive because they serve as platforms for studying fundamental scientific laws at the single-molecule level and can be used to build functional devices. Here, we present a robust methodology using anisotropic hydrogen plasma etching of graphene and in situ Friedel-Crafts acylation reaction to construct, with atomic precision, uniform covalently bonded graphene-molecule-graphene (GMG) single-molecule junctions with clear zigzag graphene edges. Applying the methodology to an azulene-type molecule, stable GMG single-molecule junctions are constructed with high yield (~82%) and high uniformity (~1.56% conductance variance over 60 devices). The reliability of the platform is shown via real-time and direct electrical monitoring of the three-level conductance fluctuation of an individual azulene molecule. This work demonstrates a universal single-molecule platform that offers countless opportunities to reveal intrinsic molecular properties and build high-performance functional molecular nanocircuits.