Synthesis and Characterization of Nano-Thick HfO₂ Memristive Crossbar

In this chapter, the geometric scaling effect is investigated on the unipolar switching behavior of nano-thick Pd(TE)/Hf (capping)/HfO₂/Pd(BE) metal-insulator-metal memristive devices. The electrical I–V characteristics of such device are studied as a function of the active area and thickness of each of the metal-oxide film and the capping layer. The device active area is shown to play a critical role in dictating the magnitude of the threshold turn-on voltage (V _ON). For (Hf-7 nm/HfO₂-10 nm) stack particularly, it is found that the average V _ON decreases from 4.7 to 2.8 V when the active area increases from 50 × 50 to 200 × 200 µm². Beyond this size, the threshold V _ON saturates and the device active area have a minimal effect on V _ON. Also, the switching ON voltage increases when the capping layer thickness increases as it adds to the total active film of the device. For the fabricated devices, decreasing the oxide thickness from 10-nm to 5-nm reduces the average turn-on voltage by 21-to-27% for 50 × 50-to-400 × 400 µm² active area range, demonstrating an improvement in the threshold power consumption of the memristor. These findings can be used to guide the design and fabrication of memristors for an improved RRAM and memristive-based applications.