On-Surface Synthesis of Single Conjugated Polymer Chains for Single-Molecule Devices

Although single-molecule electronic devices have been of great interest for several decades, the fabrication of practical circuits remains challenging due to the lack of reliable ways to wire individual molecules. On-surface synthesis of single conductive polymer chains will be a key technology to solve this problem. We already found that stimulating a molecular layer of diacetylene compound by the tip of scanning tunneling microscope (STM) could initiate chain polymerization. As a result, we could systematically fabricate a single conjugated polydiacetylene chain at designated positions. Subsequently, we developed a novel method ('chemical soldering') for connecting the conjugated polymer chains to single organic molecules. The connection of two polydiacetylene chains to a single phthalocyanine molecule was demonstrated. Nanoscale characteristics of the connection were also experimentally and theoretically investigated. Here, we briefly review tip-induced chain polymerization and the chemical soldering methods. This work will help to advance single-molecule electronics.