writer：Haiwei Tan, Hongyan Yao, Ying Song, Shiyang Zhu, Huaxuan Yu, Shaowei Guan
keywords：Hyperbranched polyimide, Memory device
source：期刊
specific source：Dyes and Pigments 146 (2017) 210-218
Issue time：2017年

In this work, a novel tetra-amine, bis (4-(3, 5-bis (4-amino-2-(trifluoromethyl) phenoxy) phenoxy) phenyl) methanone, was synthesized and then utilized to produce hyperbranched polyamic acids via polycondensation with 4, 4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). The resulting hyperbranched polyamic acids underwent termination by (4-amino) phenyl ferrocene and imidization, leading to ferrocene-terminated hyperbranched polyimide (HBPI-Fc). The resulting HBPI-Fc displayed superior solubility in conventional organic solvents and excellent thermal stability. A memory device with a configuration of indium tin oxide (ITO)/HBPI-Fc/Al was fabricated, in which the HBPI-Fc acted as the active layer. The device exhibited bistable electrical conductivity switching and nonvolatile bipolar write-once-read-many-times memory character with two threshold voltages of 2.2 V and 2.6 V, respectively, during positive and negative voltage sweep. The device exhibited an ON/OFF current ratio of 104 under a constant bias of 1.0 V and good stability in both ON- and OFF-state during the test period of 104 s. The revealed electrical bistability of the HBPI-Fc was found mainly due to the effective charge trapping effect of the electroactive terminal ferrocene groups.