Memristive Switching in Bi_1-xSb_x Nanowires

We investigated the memristive switching behavior in bismuth-antimony alloy (Bi_1-xSb_x) single nanowire devices at 0.1 ≤ x ≤ 0.42. At 0.15 ≤ x ≤ 0.42, most Bi_1-xSb_x single nanowire devices exhibited bipolar resistive switching (RS) behavior with on/off ratios of approximately 10⁴ and narrow variations in switching parameters. Moreover, the resistance values in the low-resistance state (LRS) were insensitive to x. On the other hand, at 0.1 ≤ x ≤ 0.15, some Bi_1-xSb_x single nanowire devices showed complementary RS-like behavior, which was ascribed to asymmetric contact properties. Transmission electron microscopy and elemental mapping images of Bi, Sb, and O obtained from the cross sections of the Bi_1-xSb_x single nanowire devices, which were cut before and after RS, revealed that the mobile species was Sb ions, and the migration of the Sb ions to the nanowire surface brought the switch to LRS. In addition, we demonstrated that two types of synaptic plasticity, namely, short-term plasticity and long-term potentiation, could be implemented in Bi_1-xSb_x nanowires by applying a sequence of voltage pulses with different repetition intervals.