Nonvolatile memory thin film transistors using spin-coated amorphous zinc indium oxide channel and ferroelectric copolymer

The nonvolatile memory thin film transistors (MTFTs) using a solution-processed zinc indium oxide (ZIO) active channel and a poly(vinylidene fluoride-trifluoroethylene) ferroelectric gate insulator was proposed and characterized. The spin-coated ZIO films showed good transmittance (∼90%) in the visible range. The crystalline phases are essentially amorphous even after the annealing at 400°C. All fabricated MTFTs exhibited memory behaviors based on the ferroelectric field effect in their transfer characteristics. The on/off ratio, the off current level, and the field-effect mobility were markedly varied with the changes in the annealing temperature and film composition. These differences may originate from the variations in conduction mechanism. The best device performances were obtained for the MTFT using the 83/17 mol % ZIO channel annealed at 400°C. The memory window at the V_G sweep of ±15 V, field-effect mobility, subthreshold swing, and on/off ratio were obtained to be 9.6 V, 3.3 cm² V^-1 s^-1, 0.86 V/dec, and 8.4× 10⁶, respectively. The memory on/off ratio of more than 500 was retained after a lapse of 10 h.