Achieving tunable memory performance from nonvolatile to volatile by altering the trap depth of charge trapping sites in functional imides containing carbazole moieties

Abstract

In this work, two functional imides were designed and synthesized to elucidate the influence of charge trap depth on the memory behavior. Two dianhydrides, 3,3′,4,4'-diphenylsulfonetetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride were selected as the electron acceptor considering their functional moieties of different charge-trapping depth and electron-withdrawing ability. Electrical characterization indicated that the memory devices based on the two imides exhibited nonvolatile write once read many times (WORM) memory behavior and volatile static random access memory (SRAM) behavior. Mechanisms associated with the distinct memory effect were demonstrated based on the molecular simulation. Analysis results indicated that charge trapping process is responsible for the electrical bistability and the different depth of charge-trapping sites in the two imides accounts for the distinct memory behavior of corresponding memory devices. Meanwhile, the two memory devices both show excellent long term operation stability. This paper not only reports two novel memory materials but also provided some guiding principle to the design of organic based memory devices.