Tailoring the Resistive Switching WORM Memory Behavior of Functionalized Bis(triphenylamine)
Ramesh Gayathri, Varghese Maria Angela, Panneerselvam Devibala, Predhanekar Mohamed Imran, Samuthira Nagarajan
Abstract
To better understand the structure–property relationship and the significance of the donor–acceptor (D–A) system in resistive memory devices, a series of new organic small molecules with A-π-D-π-A- and D-π-D-π-D-based architecture comprising a bis(triphenylamine) core unit and ethynyl-linked electron donor/acceptor arms were designed and synthesized. The devices with A-π-D-π-A structures exhibited write-once-read-many memory behavior with a good retention time of 1000 s while those based on D-π-D-π-D molecules presented only conductor property. The compound with nitrophenyl substitution resulted in a higher ON/OFF current ratio of 10 4, and the fluorophenyl substitution exhibited the lowest threshold voltage of −1.19 V. Solubility of the compounds in common organic solvents suggests that they are promising candidates for economic solution-processable techniques. Density functional theory calculations were used to envision the frontier molecular orbitals and to support the proposed resistive switching mechanisms. It is inferred that the presence of donor/acceptor substituents has a significant impact on the highest occupied molecular orbital–lowest unoccupied molecular orbital energy levels of the molecules, which affects their memory-switching behavior and thus suggests that a D–A architecture is ideal for memory device resistance switching characteristics.