Nonvolatile Electrical Switching and Write-Once Read-Many-Times Memory Effects in Functional Polyimides Containing Triphenylamine and 1,3,4-Oxadiazole Moieties

This work reports the synthesis and characterization of a series of functional aromatic polyimides (OXTA-PI)s containing triphenylamine and 1,3,4-oxadiazole moieties. All the polyimides exhibit high glass transition temperatures of 309-319 degrees C. A resistive switching device with the sandwich structure of indium tin oxide/polymer/Al was fabricated using the soluble polyimide from 4,4'-hexafluoroisopropylidene-diphthalic anhydride (OXTA-Pla). The device exhibits two conductivity states and can be switched from the initial low-conductivity (OFF) state to the high-conductivity (ON) state at the threshold voltages of 1.8 V under both positive and negative electrical sweeps, with an ON/OFF state current ratio in the order of 10(5). The ON state of the device is nonvolatile and can withstand a constant voltage stress of -1 V for 6 h and 10(8) pulse read cycles at -1 V under ambient conditions. Upon reversing the bias, the ON state cannot be reset to the initial OFF states. The nonvolatile and inerasable nature of the ON state, as well as the ability to write, read, and sustain the electrical states, fulfills the requirements of a write-once read-many-times (WORM) memory.