Preparation and memory performance of a nanoaggregated dispersed red 1-functionalized poly (N-vinylcarbazole) film via solution-phase self-assembly

Abstract

A nanoaggregated dispersed red 1-grafted poly(N-vinylcarbazole) (abbreviated PVDR) is self-assembled via π - π stacking interactions of the carbazole groups in the polymer system after adding a solution of PVDR in N,N-dimethylformamide to dichloromethane. Upon self-assembly, the nanoaggregated PVDR film displays helical columnar stacks with large grain sizes, whereas a non-aggregated PVDR film exhibits an amorphous morphology with smaller grain size. A write-once read-many-times (WORM) memory device is shown whereby a pre-assembled solution of PVDR is spin-coated as the active layer and is sandwiched between an aluminum electrode and an indium-tin-oxide (ITO) electrode. This device shows very good memory performance, with an ON/OFF current ratio of more than 105 and a low misreading rate through the precise control of the ON and OFF states. The stability of the nanoaggregated PVDR device is much higher than that of the non-nanoaggregated PVDR device. This difference in device stability under constant voltage stress can be mainly attributed to the difference in the film crystallinity and surface morphology. No degradation in current density was observed for the ON-and OFF-states after more than one hundred million (108) continuous read cycles indicating that both states were insensitive to the read cycles. These results render the nanoaggregated PVDR polymer as promising components for high-performance polymer memory devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.