A recent spike in demand for semiconductor memories has been spurred by the quick development of big data and the internet of things. Numerous new non-volatile memory technologies are being explored closely to provide larger memory densities and improved performance as NAND flash scaling approaches its physical limits. Resistive random-access memory (RRAM), one of them, has sparked the most attention since it can get around flash memory's intrinsic restrictions while simultaneously providing affordability, reliable performance, and a tiny footprint. Despite its promising attributes, there are still several issues that need to be resolved before RRAM technology can be further developed and commercialized. First of all, it is challenging to maximize the device's performance due to the incomplete understanding of the physical mechanics underlying resistance-change occurrences. Second, there should be improvements made to the reliability of RRAM in a number of areas, including the variability of switching settings, the retention/endurance problems brought on by the unpredictable nature of filament development, and the necessity of a high voltage forming process.
Factor (or the technique) to improve the performance and understanding of switching mechanism of binary oxide and emerging perovskite-based RRAM for its transparent, flexible, cryogenic, and neural network application is exhibited in this study. The Ta2O5 based RRAM devices fabricated via RF sputtering at room temperature on the rigid and transparent flexible substrate, exhibits a high optical transmittance (82%), ROFF/RON ratio of ≈10³, SET voltage of (0.37 ± 0.08)V, RESET voltage of -(2.83 ± 0.42)V, good endurance of ≈10³ cycles and retention over 10⁴s at room temperature (RT) as well as 80 ℃. Resistive switching from 333 K to cryogenic temperature 150 K is confirmed, implementation of devices on flexible ITO-PET substrate with ROFF/RON ratio of ≈10², reasonable endurance of ≈500 cycles, and retention over 10⁴s at RT.
The reliable and uniform memory properties for bilayer ITO/IGZO/ZrO₂/Ti based RRAMs with (92 ± 2) nm IGZO films achieved a stable switching up to 10³ cycles, ROFF/RON ratio ~10², and retention for 10⁴s. The IGZO plays a key in the RRAM performances improvement, which is interpreted with oxygen vacancy in the layer, acting as oxygen reservoir owing to its oxygen-deficient composition to absorb/discharge oxygen ions. With respect to the switching mechanism, set cycles are governed by a trap-mediated space-charge-limited current (SCLC) conduction. The optimized device configuration implementation on flexible substrate shows switching up to 10³ cycles, ROFF/RON ratio (>10), and retention for 10⁴ s, along with the stable performance under different bending radii
Furthermore, the switching properties of lead free Cs2SnI6 perovskite-based RRAMs device fabricated by simple drop casting method demonstrated an endurance up to 300 cycles, ROFF/RON ratio >10³, and retention for 10⁴ s. It also shows a self-compliance property, 6-stage multilevel storage capability with endurance up to 10⁴ s and stable switching under cryogenic temperature (173 K). The device implemented on flexible substrate shows switching up to 100 cycles, ROFF/RON ratio (>10²), and retention for 10⁴ s, along with the stable resistive state under different bending radii over 200 bending cycles. Furthermore, the device used for BNN process shows its applications toward flexible neural network system.