Transition metal oxide based resistive random-access memory: An overview of materials and device performance enhancement techniques

The emergence of the big data era has led to enormous demand for memory devices that are low cost, flexible, fabrication friendly, transparent, energy efficient, and have a higher density. Resistive random-access memory (RRAM) is an outstanding emerging non-volatile memory technology that has the potential to change the avenue of future storage devices. It is a promising technology owing to its attributes like minimal power usage, simple structure, long endurance cycles, high retention time, integrability with the existing complementary metal oxide semiconductor process (CMOS), and excellent scalability. It is highly attractive for several applications like neuromorphic computing, Internet of Things, non-volatile logics, hardware security, and radiation hardened electronics. Despite significant advances in the field of RRAM, materials and recent advanced techniques to enhance its performance have not been reviewed in detail. This paper provides an in-depth review of recent advancements in the field of RRAM, including the material used for fabrication and the methods to enhance the device performance. Advanced materials, especially transition metal oxides like copper oxide, nickel oxide, zinc oxide, tantalum oxide, titanium oxide, and hafnium oxide, used to fabricate RRAM devices are reviewed and their impacts on the performance have been discussed. The key figure of merits such as endurance, retention, and multi-bit capability are studied in relation to resistive switching memories. Several methods such as structure engineering, doping, annealing, light irradiation, plasma treatment, and ion irradiation used to enhance devices' performance are discussed. Furthermore, the impact of low and high energy ion irradiation on RRAM's electrical performance is provided in detail. Finally, this paper provides directions for future research in this field based on the findings of this review.