Chemical soldering holds promise for single molecule electronics

Led by Yuji Okawa of the National Institute for Materials Science in Tsukuba, Japan, the team developed a method to wire and bond single molecules by first depositing a small amount of phthalocyanine - a macrocyclic compound commonly used in organic semiconductors - and solar cells on a monomolecular film of a diacetylene on a graphite substrate. Once nanoclusters were formed on the surface, the researchers brought the tip of a scanning tunnelling microscope to one of the phthalocyanine molecules and applied it to a pulsed voltage across the tip and surface. This initiated chain polymerisation of the diacetylene and formed a polymer nanowire that bonded to the phthalocyanine molecule. The researchers named this spontaneous reaction 'chemical soldering'. "The key to single molecule electronics is connecting functional molecules to each other using conductive nanowires," explained Okawa. "This involves two issues; how to create conductive nanowires at designated positions, and how to ensure chemical bonding between the nanowires and functional molecules. Here, we present a novel method that solves both issues." While Okawa maintained that the research is unlikely to bring single molecule electronics to the market any time soon, he said his next challenge is to test phthalocyanine molecules as diodes and to try wiring up other molecules. "The final goal of our research is to fabricate and demonstrate a single molecule electronic circuit," he concluded.