Formation characteristics of the devices under NF and PF, and I-V characteristics for NF and PF devices. (a) Formation characteristics of the pristine resistive memory devices under NF and PF. (b) Typical I-V hysteresis characteristics for the NF devices at RT. (c) Typical I-V characteristics with stable switching for the PF devices at RT. Statistical distribution of the NF and PF devices for (d) set/reset voltages and (e) LRS/HRS. (f) Consecutive 100 DC cycles at 85°C for the PF devices.