Conductive polymer patterning on a photoswitching polymer layer

Abstract

Patterning of conductive organic thin films in a nanometer level is crucial for the application of many functional organic materials in electronic devices. The conventional photoresist processing used in inorganic device patterning requires etching, which often degrades many functional organic materials during the process and prevents correction or erasure of the formed image. Several other patterning methods have been demonstrated, including laser ablation, direct laser patterning by two-photon polymerization, ink-jet printing, photolithographic undercut formation, dry-film lift-off, electron-beam lithography, and conformal masking using elastomeric membranes. Compared with the current method, conductive pattern formation through photoisomerization should be especially interesting because the pattern formed by photoisomerization is erasable and eventually controls the growth of the conductive polymer in the electropolymerization process. Photochromic materials that exhibit reversible electrical switching properties via photo-isomerization reactions can bring about a new method of electrode patterning by selectively irradiating the desired area through a mask. Although much progress has been seen in photochromic materials and their switching properties due to extensive study on them, hardly any study has been performed on micropatterning and the controllability of conducting layer growth utilizing photo-induced conductivity change. This study presents the growth of a conducting polymer film on a photochromic thin film which controls thickness of conductive polymer layer. Direct patterning of an organic conductive polymer could be formed through the photoisomerization of a diarylethene polymer (1), followed by the electropolymerization of an electroactive monomer such as 1,4-bis(2-[3',4'-ethylenedioxy]thienyl)-2-methoxy-5-2"-ethylhexyloxybenzene (BEDOT-MEHB) (2). The advantages of this method are its capabilities for generating device patterns scale using a simple, rapid and non-destructive process. Also demonstrated herein are the growth and fabrication of conductive polymer arrays with thicknesses ranging from 2 to 400 nm.