Optimized thickness on resistivity switching of the solution-derived HfO2 device

The effects of solution-derived HfO2 film thickness on the resistive switching and conduction mechanism of Ag/HfO2/Pt memory devices were investigated. The device exhibited improved operating voltage stability with an optimized HfO2 thickness of approximately 75 nm. As a result, a low set voltage of 0.17 V, a reset voltage of 0.08 V, and a high-to-low resistivity ratio exceeding 100 are derived. The read and write performance was also found to be stable and repeatable. As the HfO2 thickness increased, the resistive switching transitioned from positive unipolar to bipolar. The set voltage decreases initially and then increases, while the reset voltage gradually increases. The positive unipolar resistive switching was attributed to thermal rupture caused by Joule heating. The decrease in grain boundary leads to a reduction in ion migration channels and defect centers, resulting in a narrower and more restricted distribution of the set voltage. Similarly, the varied ion migration channels, trapping of the grain boundary, and required electric field for the reversal migration of Ag ions during the reset process are responsible for fluctuations in value and a monotonic decrease in reset voltage with increasing HfO2 thickness.