Direct nanoscale patterning of in-plane-aligned polymer via split-tip NSOM

Polymer electronic devices have been developed for a wide array of applications, including LEDs, organic transistors, solar cells, and more. These devices display ordered regions, where the conducting carbon-carbon backbones all line up in the same direction, and disordered regions, where the carbon-carbon backbones are tangled. Here, we demonstrate the ability to fabricate the ordered regions of a polymer. When placed in a high humidity environment, the polymers in a water-soluble poly(phenylene vinylene) (PPV) precursor film become reorientable. To control this orientation, we use a split-tip, near-field scanning optical microscope (NSOM) system. The split-tip applies a high, localized electric field in the plane of the surface, and subjects that region to UV light. When wet, the electric field forces the polymers to align beneath the tip, and the UV light engenders insoluble PPV, preventing loss of alignment. We align a large rectangular region by scanning a probe using this technique, and use cross-polarization measurements to demonstrate alignment. The ability to fabricate ordered layers removes material variations from studies of conduction and interfacial phenomena, thus represents a significant step towards measuring the intrinsic properties of conducting polymers.