Eradicating negative-Set behavior of TiO₂-based devices by inserting an oxygen vacancy rich zirconium oxide layer for data storage applications

Memristors, with low energy consumption, long data storage and fast switching speed, are considered to be promising for applications such as terabit data storage memory and hardware based neurocomputation applications. However, unexpected negative-Set behavior is a serious issue that causes deterioration of reliability and uniformity of switching parameters. In this work, negative-Set behavior of TiO₂-based RRAM is successfully eradicated by inserting a thin oxygen vacancy rich ZrO_2-x layer. In addition, oxygen vacancy rich ZrO_2-x layer is also responsible for the enhancement of resistive switching characteristics in terms of excellent endurance performance (2000 DC cycles), good data retention upto 10⁴ s and uniformity in Set/Reset voltages. Experimental results and density functional theory (DFT) analysis confirm that an interface layer TiO_x has formed between highly reactive electrode (Ti) and ZrO₂ interlayer. This interface layer is serving as a low series resistance layer and oxygen ion reservoir in Set-process and oxygen ions supplier in Reset-process to generate/refill the oxygen vacancies in the formation and rupture of conductive filaments. Comparing with the single layer Ti/TiO₂/Pt device, it is noteworthy that the switching process in the bilayer (BL) Ti/ZrO_2-x/TiO₂/Pt memristor device is not affected even at high Reset-voltages, but the negative-Set behavior has been eradicated effectively. This work demonstrates that the insertion of a thin oxygen vacancy rich ZrO_2-x interlayer into TiO₂-based devices is a feasible approach to solve unpredicted negative-Set behavior of RRAM devices.