I-VGtransfer characteristics. Typical I-VG transfer characteristic was measured at (a) 300, (b) 140, (c) 80, and (d) 8.5 K (with VDS = 2 V for a to c; VDS = 50 mV for d). In (a), a counterclockwise hysteresis loop occurs at room temperature due to a charge-store effect. In (b), at 80 K, a clockwise hysteresis loop is opened, indicating a nonvolatile memory operation. In (c), a competition between the ferroelectric effect and the charge-storage effect essentially closes the memory window at 140 K. In (d), at 8.5 K, a ferroelectric-modulated SET behavior is observed. The two red circles represent a bistable state. The sharp increase at a gate voltage of −6 V is due to the leakage current.
Liu et al. Nanoscale Research Letters 2012 7:285 doi:10.1186/1556-276X-7-285