Abstract:

Resistive switching devices have the advantage that the resistance can be repeatedly regulated between two or more resistance states. As a new resistive switching device, a memristor has abundant resistance states that can be continuously tuned. In recent years, memristors have been extensively studied for emerging nonvolatile memories and in the construction of neuromorphic systems owing to their simple two-terminal structure, high integration, and low operating voltage compared with those of traditional metal-oxide-semiconductor field-effect transistors. However, their application is limited owing to their relatively poor reliability. Recently, several studies have shown that two-dimensional materials such as graphene oxide can optimize the memristor performance. A new two-dimensional material, MXene, also exhibits special mechanical and electrical properties that show promise for use in memristors owing to its two-dimensional layered structure similar to that of graphene. MXene is a two-dimensional transition metal carbide/nitride of the form M_n+1X_n, where M is an early transition metal and X is carbon or nitrogen. Its other characteristics such as hydrophilic surfaces and ultrahigh metal conductivity (6000–8000 S·cm^-1) have been studied, and it has been applied to energy storage devices and electronic devices such as supercapacitors and secondary batteries. However, the application of MXene in resistive devices has been rarely investigated, especially for memristors. In this study, we prepared Ti₃C₂ powder by etching layered compounds of Ti₃AlC₂ with a mixture of HCl and HF. Next, Ti₃C₂ film was introduced into the memristor structure by spin-coating. The physical characteristics of Ti₃C₂ were investigated and analyzed by X-ray diffraction and scanning electron microscopy, and a memristor with Cu/Ti₃C₂/SiO₂/W structure was fabricated. In this structure, Ti₃C₂ and SiO₂ were introduced as resistive layers, and related electrical properties were investigated. Under dual DC voltage sweeping, the typical switching characteristic curves of the memristor were measured. Moreover, the repeatability and stability of high- and low-resistance states were investigated and analyzed, respectively. The experimental results show that the device can maintain stable high- and low-resistance states for > 10⁴ s during 100 dual-voltage sweeping cycles. In addition, the device can be regulated by a pulse voltage and realize typical paired-pulse facilitation that is similar to biological synapses. This work proved that the Cu/Ti₃C₂/SiO₂/W memristor has huge potential for application in the construction of emerging memory devices and artificial neuromorphic systems.

Key words: Resistive switching device, Memristor, Wet etching, MXene, Conductive performance, Conductive mechanism