Nanopatterning and Fabrication of Memory Devices from\nLayer-by-Layer Poly(3,4-ethylenedioxythiophene)−Poly(styrene\nsulfonate) Ultrathin Films

Abstract

A write−read−erasable memory device was fabricated on layer-by-layer (LbL) ultrathin films prepared from\npoly(3,4-ethylenedioxythiophene)−poly(styrene sulfonate) (PEDOT−PSS) and poly(diallyldimethylammonium chloride)\n(PDDA). By use of current-sensing atomic force microscopy (CS-AFM), nanopatterns were formed by applying a\nbias voltage between a conductive tip (Pt-coated Si₃N₄ cantilever) in contact with the polymer film and gold substrate.\nThe dependence of the nanopatterns on film thickness, applied bias, and writing speed was studied. Moreover, the\nheight of the patterns was 3−5 times higher than the original thickness of the films, opening the possibility for\nthree-dimensional nanopatterning. The ability of the patterns to be erased after nanowriting was also investigated. By\ncomparing the <i>I</i><i>−</i><i>V</i> characteristics under ambient conditions and under N₂ environment, a joule-heating activated,\nwater meniscus-assisted anion doping mechanism for the nanopatterning process was determined. Write−read−erase\nmemory device capability was demonstrated on the nanopatterns.