Abstract
A polydiacetylene nanowire fabricated on a highly ordered pyrolytic graphite surface was studied by scanning tunneling microscopy/spectroscopy (STM/STS). The spectroscopy of individual polydiacetylene nanowires revealed the theoretically predicted π-band and band edge singularities, which are characteristics of a one-dimensional π-conjugated polymer. Furthermore, under a high electric field intensity applied to the polymer wire, the spectrum shows a narrow band gap caused by polaron injection. When a much higher electric field intensity was applied to the wire, an avalanche current flow that rises abruptly has been observed. We consider that such a large current flow originates from an electrical property of the polymer wire, which was changed by a dynamical modulation of the injected polaron.