Stabilized and RESET-voltage controlled multi-level switching characteristics in ZrO2-based memristors by inserting a-ZTO interface layer

Abstract

Transition metal oxides based memristors possess multi-resistance states and can be used as a main source for memory devices. However, variability in resistive switching (RS) characteristics is a major issue for the application of memristor devices in emerging information computing system. The achievement of stable switching between high resistance state (HRS) and low resistance states (LRS) has become an important task for their implementation and industrial production. In this study, issues of oxygen accumulation and variations in the HRS of single layer (SL) Ta/ZrO2/TiN memristor devices, stability of HRS and concentrated distribution of SET-voltages were realized by inserting a thin amorphous zinc-tin-oxide (a-ZTO) film between the TiN bottom electrode and ZrO2 RS layer. With this bilayer (BL) Ta/ZrO2/a-ZTO/TiN memristor device, stabilized RS properties, such as ON/OFF ratio >10(2), smaller forming voltages, uniform SET-/RESET-voltages, and good pulse switching endurance (>10(5) cycles) have been demonstrated as compared to SL memristor devices. In addition, BL memristor device also exhibited four distinct resistance levels (three high resistance levels with same LRS) by adjusting RESETstop voltages, and each level showed multilevel endurance and reliable retention characteristics. The current transport mechanism has been investigated at HRS of different RESET-stop voltages (i.e. 1.5 V, 1.7 V and 1.9 V), which confirms that Schottky barrier height increases by increasing the RESET-voltages. Finally, a conducting model was proposed to illuminate the effect of a-ZTO thin layer and to explain the physical mechanism of stabilized RS behavior. (C) 2020 Elsevier B.V. All rights reserved.