Improved analog switching characteristics of TaO-based memristor using indium tin oxide buffer layer for neuromorphic computing.

A memristor is defined as a non-volatile memory switching two-terminal resistor, and a memristor with digital switching characteristics is widely studied as a next-generation non-volatile memory because of its simple structure, high integration density, and low power consumption. Recently, analog memristors with gradual resistance switching (RS) characteristics have garnered great attention because of their potential to implement artificial synapses that can emulate the brain functions. Transition metal oxides are thought to be strong candidate materials for the RS. In particular, tantalum oxide (TaO)-based memristive devices provide stable and durable switching characteristics. TaO-based memristors utilize analog switching characteristics and have excellent durability and reliability, so they can be applied as artificial synaptic device. In this study, the characteristics of analog RS using TaO-based memristive devices were investigated. The current level of the Pt/TaO/Pt memristors was improved by adjusting the thickness of TaO. In particular, when an indium-tin-oxide (ITO) buffer layer was added to TaOforming a Pt/ITO/TaO/Pt heterostructured double-layer device, it showed more symmetrical potentiation and depression characteristics under both polarities than a single-layer device without ITO layer. The symmetrical and linear potentiation and depression characteristics are essential for the development of efficient memristor-based neuromorphic systems. Insertion of the ITO buffer layer improves linearity, symmetry, and stability of the analog RS properties of TaO-based memristors to artificial synapses.