(363d) Maskless Electrodeposited Contact to Conducting Polymer Nanowires

One-dimensional (1-D) nanostructures, such as nanowires (NWs) and nanotubes (NTs), are attractive materials for sensors and spintronic devices because of their potential for device miniaturization and unique properties which arise from size dependent quantum confinement effects. These building blocks of nanotechnology can be further complexed with axial and radial interfaces, for segmented, multilayered, or core/shell structures. Additionally, the use of polymeric constituents has attracted interest as hybrid organic/inorganic nanostructures have demonstrated enhanced functionalities for logic and sensing applications. However, lithographic contact of assembled nanostructures is a bottleneck procedure increasing processing time and complexity with alignment requirements. Moreover, the seemingly benign lithographic processing conditions can be harsh environments for organic materials, subjecting the nanowires to high intensity ultra violet light and organic solvents that may permanently degrade, stress, or dissolve polymeric nanowire surfaces.

This work investigates a post-assembly electrodeposition technique to create core/shell hybrid polymer/ferromagnetic structures and single conducting polymer nanowire devices. Polyethylenedioxythiophene (PEDOT) and polypyrrole (Ppy) nanowires were synthesized by template directed electrodeposition and dielectrophoretically assembled on prefabricated Au electrodes. The single wire devices were subsequently electroplated with different selectivities ranging from complete coating of both nanowire and electrodes to a discriminating electrodeposition, which occurs solely on the electrodes to embed the nanowire ends. The high resistance of the polymer nanowire was critical for selective deposition, inhibiting electrodeposition on the wire. The applied potential and plating electrolytes were also found to have a significant impact on the substrate selectivity. Different dopants were also investigated to understand the polymer reduction during cathodic metal deposition. Selective Au and Ni electrodeposition was used to integrate PEDOT and Ppy nanowires, respectively, with solid mechanical joints and intimate contact for single nanowire devices. Electrical and gas sensing properties for these devices are reported herein. Hybrid core/shell nanostructures were also fabricated by electrodepositing of Ni on PEDOT and were show to have unique angle dependent magnetotransport properties.