ZnO nanowire-based nonvolatile memory devices with Al2O3 layers as storage nodes

Top-gate ZnO nanowire field-effect transistors (FETs) with Al2O3 gate dielectric layers as storage nodes were fabricated and their memory effects were characterized in this work. The Al2O3 layers deposited on the ZnO nanowire channels were utilized not only as gate dielectric ones but also as charge trapping ones. For a representative top-gate ZnO nanowire FET, its I(DS)-V(GS) characteristics for the double sweep of the gate voltages exhibit the counterclockwise hysteresis and the threshold voltage shift. The gate voltage in the pulse form was applied for 1 s, and the threshold voltage shift of I(DS)-V(GS) characteristics was extended from 0.3 to 0.8 V compared with that for the double sweep. In this ZnO nanowire FET, negative charge carriers originated from the gate electrode are stored in the Al2O3 layer for applied negative gate voltages, and they are extracted for applied positive gate voltages.