Atomic-scale analysis of polydiacetylene nanowires by scanning tunneling microscopy

Scanning tunneling microscopy (STM) has been used to study polydiacetylene nanowires, a candidate material for molecular electronic interconnects. STM analysis across different voltages shows that the substrate material contributes to hole doping in the nanowires. Changing the substrate material causes a substantial change in the apparent height of the nanowires in STM images, revealing a previously-overlooked dependence of the electronic structure upon the substrate electrode material. Polydiacetylene nanowires are also shown to desorb due to interactions with the STM tip. These nanowires can either fully desorb or be cut into shorter segments depending on the strength of the tip-nanowire interaction. In both desorption cases the surrounding diacetylene-derivative monolayer order is fully restored within 100 ms. Desorption is a critical factor in evaluating the stability of these nanowires.