Design and synthesis of pyridine-bridged benzothiazole-based D-A system for SRAM memory devices

Abstract

This study focused on designing small donor-acceptor (D-A) frameworks for resistive memory devices. We synthesized five new organic molecules using pyridine bridged to benzothiazole and various donor moieties (triphenylamine, naphthalene, benzothiophene, t-butyl phenyl, and mesityl group) via Suzuki cross-coupling to study their memory performance. The compounds with triphenylamine and naphthalene exhibited good semiconductor behavior, with a band gap of 3.11 eV and 3.44 eV, respectively. The benzothiazole moiety, employed as a shallow trap in the acceptor segment, demonstrated the SRAM characteristics of all devices. This study examined how varying the potency of electron-donating substituents impacts charge transfer and volatile memory behavior in a small D-A system. Memory devices with triphenylamine and naphthalene donors showed binary SRAM behavior with high ON/OFF ratios of 2.82 × 103 and 2.36 × 103, while t-butylphenyl and mesityl donors exhibited lower ratios of 1.43 × 101 and 4.08 × 101, respectively. All the compounds exhibited switching characteristics at a low threshold voltage of −1 to −1.3 V. The analysis of HOMO, LUMO energy levels, and ESP images of all compounds from the DFT study, collectively indicate charge transfer and trapping are the operative mechanisms in volatile SRAM devices.