Tuning memory performances from WORM to flash or DRAM by structural tailoring with different donor moieties

Abstract

Four donor–acceptor organic molecules (HATT, HDTT, HETT and HRTT) consisting of different electron donors (phenol, triphenylamine, benzene and carbazole) and the same electron acceptor (triazole) were used as the active layer in NVM (nonvolatile memory) devices. I–V measurement showed that the ITO/HATT/Al and ITO/HETT/Al devices presented write-once-read-many-times (WORM) characteristics, TO/HDTT/Al exhibited a stable flash-type effect and ITO/HRTT/Al device showed a volatile dynamic random access memory (DRAM) switching behaviour. These performances were well preserved when the electrodes changed to Pt. To elucidate the mechanisms associated with tunable memory behaviours, the effects of films/electrode interfaces and molecular simulation results were systematically investigated. We assigned memory effects to the differences in donor moieties. This study demonstrated that the electrical behaviours of organic materials could be switched by simply replacing electron-rich groups with different charge delocalization abilities induced by the effect of electron donating ability and conjugation under an applied voltage, which would provide a guideline for designing of new materials with multitype high-performance memories.