Atomic-Scale Spectroscopy of Polydiacetylene Nanowires

In recent years, the appeal of organic electronic devices has spurred interest in conducting polymers, such as polydiacetylene. Polydiacetylene nanowires offer numerous possibilities for application in molecular electronics, and they are a model system for understanding conduction mechanisms in polymers. We have used scanning tunneling microscopy to investigate monolayer films of pentacosadiynoic acid formed on highly ordered pyrolytic graphite using the Langmuir-Blodgett and Langmuir-Schaeffer deposition techniques and subsequently polymerized to form polydiacetylene nanowires. By applying a novel method of microwave frequency mixing at the STM tip junction, we have obtained capacitance-voltage spectroscopic data to characterize the wires across a range of bias voltages, tunneling gap resistances, and microwave mixing frequencies.