Memory characteristics of anthracene-based polyimides in non-volatile resistive memory devices

Abstract

Recently, polyimides (PIs) containing the anthracene moiety have been demonstrated to show a wide range of electrical bistable switching behavior, depending on the chemical structures or electrode materials used in the memory devices. There is a need to develop advanced anthracene-containing PIs having higher memory performance. In this study, a new anthracene-containing diamine, 4-(anthracen-9-ylmethoxy)-1,3-diaminobenzene (AMDA), was synthesized, and polymerized with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) to prepare 6FDA-AMDA PI. For comparison, another PI (6FDA-AnDA PI) was prepared from 6FDA and 2,6-diaminoanthracene (AnDA). 6FDA-AMDA PI and 6FDA-AnDA PI have anthracene moieties in the side and main chains, respectively. 6FDA-AMDA PI showed higher solubility in common organic solvents and less tendency of gelation compared to 6FDA-AnDA PI. The prepared PIs exhibited excellent thermal stability. The Al/6FDA-AMDA PI/indium tin oxide (ITO) device showed write-once-read-many times (WORM) behavior with an on/off ratio up to 10⁶, a threshold voltage of 2.40 V, and a high device yield of 80%. In contrast, the Al/6FDA-AnDA PI/ITO device exhibited WORM behavior with an on/off ratio of up to 10⁴, a threshold voltage at 2.50 V and a 20% device yield. The mechanisms associated with the memory effect are explained using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The lower switching voltage and higher device yield of 6FDA-AMDA PI may be attributed to more effective inter-chain charge transfer of the side-chain PI, compared to the main chain PI (6FDA-AnDA PI). This study demonstrates that the 6FDA-AMDA PI is suitable as an active material for solution-processable non-volatile memories.