Near-field optical lithography of a conjugated polymer

We report the fabrication of poly(p-phenylene vinylene) nanostructures by direct scanning near-field lithography of its soluble precursor. The technique is based on the spatially selective inhibition of the precursor solubility by exposure to the ultraviolet optical field present at the apex of scanning near-field fiber probes with aperture diameters between 40 and 80 nm (+/-5 nm). After development in methanol and thermal conversion under vacuum we obtain features with a minimum dimension of 160 nm. We demonstrate the use of the technique for the direct writing of two-dimensional photonic crystals with intentional defects and a periodicity relevant to applications in the visible range. Using a Bethe-Bouwkamp model, we then discuss the influence of probe size, tip-sample distance, and film thickness on the resolution of the lithographic process. We also discuss limitations to the resolution that can arise from physical properties of the lithographic medium. (C) 2003 American Institute of Physics.