Pseudo-flexible resistive switching characteristics of nano-bowl-like NiO arrays on mica substrates

Abstract

Nano-bowl-like NiO (nb-NiO) arrays on flexible Pt-coated mica substrates have been fabricated by electro-deposition and magnetron sputtering with the assistance of the monolayer colloidal sphere template. The nano-bowl array makes the polycrystalline NiO film thickness change periodically in the range of 150–450 nm, and the HfO2 buffer layer effectively depresses the local leakage current. A voltage which is lower than ±0.4 V can make the Ag/HfO2/nb-NiO/Pt cell reversibly switch between the high and the low resistance states within 11 μs. This cell exhibits a ratio of the high to the low resistance (RH/RL) of 103 ∼ 104, a data retention time over 104 s and an endurance of >1200 cycles. Driven by the non-uniform electric field, oxygen ions accumulated at the HfO2/NiO interface prefer to occur the Fowler-Nordheim tunneling at the thinnest bowl bottom, which decreases switching voltages. The bent cell almost keeps initial resistive switching properties before the bending radius (r) is below 2.5 cm. Though its properties greatly degrade when the r further reduces below 1.5 cm, it can recover most of initial memory window after returning to the flat state again, showing potential applications in new types of pseudo-flexible memory devices.