Comparative investigation of unipolar resistance switching effect of Pt/Mg0.6Zn0.4O/Pt devices with different electrode patterns for nonvolatile memory application

Abstract

Electrically induced unipolar resistance switching effects of Mg 0.6 Zn 0.4 O thin films with two top Pt electrodes (MZO-T) and top and bottom Pt electrodes (MZO-B)were demonstrated and compared for nonvolatile memory applications. The obtained resistance ratios of highresistance states (HRS) to low-resistance states (LRS) for MZO-B and MZO-T devices were above seven and four orders of magnitude, respectively, and exhibited a slight degradation with voltage. For both the devices, the conduction mechanisms were dominated by ohmic conduction in LRS and trap-controlled space charge limited current in HRS. Furthermore, a filamentary model was applied to explain the switching behaviors for both the devices considering the asymmetric interface defects and film thickness. The results also suggest that resistance switching behaviors can be regulated by interface defect engineering.Reversible resistance switching effects between high-resistance states (HRS) and low-resistance states (LRS) in metaloxide-metal devices have attracted much attention due to their promising application for future nonvolatile memory devices such as resistance random access memories (RRAMs) [1][2][3][4]. Although various possible physical mechanisms have been proposed to explain these resistance switching effects, the underlying origin of the resistive switching is still a controversial issue. However, more and more investigations suggested the intimate relationship of resistive switching effects with defects in oxide thin films, such as TiO 2 [1], NiO [4], SrTiO 3 [2], and so on.ZnO-based thin films are also promising candidate oxide materials for RRAMs. So far, the resistance switching effects of ZnO-based films such as ZnO [5, 6], S-and Codoped ZnO [7], and Mg 0.2 Zn 0.8 O [8] have also been reported. To enhance the signal-to-noise of the devices, the ultra-high resistance ratio of HRS to LRS of about nine orders of magnitude was obtained in the spinel-MgZnO thin film with high Mg content [9]. Generally, the simple capacitor-like sandwich device structure was applied to investigate the resistance switching effects. For this, the thin films were always integrated directly on the conductive bottom electrode under certain conditions by various deposition techniques, while the top electrodes were usually deposited on the thin-film surface without annealing. Therefore, the devices can be achieved between top and bottom electrodes as well as between two top electrodes. However, due to the different processing conditions, asymmetrical top and bottom metal/film interface characteristics were believed. Although the resistance switching effects of metal-oxidemetal devices with the two electrode patterns above have been reported previously, there are few reports on the comparative investigation between them.In this study, we successfully deposited spinelMg 0.6 Zn 0.4 O thin films on Pt/TiO 2 /SiO 2 /Si substrates by the sol-gel spin coating technique. The unipolar colossal resistance switching behaviors were observed in the capacitorlike Pt/spinel-Mg 0.6...