Synthesis and binary/ternary write-once read-many-times electrical memory behaviors of carbazole-based polyimides bearing flexible linkage segment

An efficient and readily available novel carbazole-based aromatic diamine was synthesized and characterized. Two polyimides (PI-a and PI-b) were prepared via a two-step procedure using the new synthesized diamine reacting with low-cost and the commercialized pyromellitic dianhydride (PMDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), respectively. PIs were characterized and exhibited highly organo-solubility and thermal stability. The Al/PI-a/ITO device showed binary write-once read-many-times (WORM) behavior with an ON/OFF current ratio up to 10⁹ and the threshold voltage as low as −0.21 V, whereas the Al/PI-b/ITO device presented ternary WORM behavior with an ON2/ON1/OFF current ratio up to 10⁵:10⁴:1 and the switching voltage below −3 V. The memory switching mechanisms were further elucidated through molecular simulation based on the density functional theory (DFT) method. This provides an effective strategy to achieve a ternary memory device.