Nonvolatile memory devices based on undoped and Hf- and NaF-doped ZnO thin film transistors with Ag nanowires inserted between ZnO and gate insulator interface

Abstract

Nonvolatile memory devices based on solution-processed thin film transistors (TFTs) of sol–gel-derived undoped ZnO and ZnO doped with Hf and NaF incorporating Ag nanowires (AgNWs) as charge trapping media between the ZnO and insulator interface are demonstrated. The transfer characteristics of the devices exhibited a large clockwise hysteresis due to the carrier trapping at the AgNWs between the ZnO and dielectric interface. The memory devices showed a remarkable, wide, programmable memory window during program/erase operations, which is attributed to the charge carrier trapping and de-trapping in the ZnO/AgNW/SiO₂ structure. The device based on Hf-doped ZnO exhibited a larger memory window compared to the device based on NaF-doped ZnO. The threshold voltage shifts of these devices measured over various durations exhibited a large memory window. The fabricated transistor memory devices showed long term retention time characteristics, indicating excellent electrical reliability and stability.