Interface-Engineered Amorphous TiO2-Based Resistive Memory Devices

Abstract

Crossbar-type bipolar resistive memory devices based on low-temperature amorphous TiO2 (a-TiO2) thin films are very promising devices for flexible nonvolatile memory applications. However, stable bipolar resistive switching from amorphous TiO2 thin films has only been achieved for Al metal electrodes that can have severe problems like electromigration and breakdown in real applications and can be a limiting factor for novel applications like transparent electronics. Here, amorphous TiO 2-based resistive random access memory devices are presented that universally work for any configuration of metal electrodes via engineering the top and bottom interface domains. Both by inserting an ultrathin metal layer in the top interface region and by incorporating a thin blocking layer in the bottom interface, more enhanced resistance switching and superior endurance performance can be realized. Using high-resolution transmission electron microscopy, point energy dispersive spectroscopy, and energy-filtering transmission electron microscopy, it is demonstrated that the stable bipolar resistive switching in metal/a-TiO2/metal RRAM devices is attributed to both interface domains: the top interface domain with mobile oxygen ions and the bottom interface domain for its protection against an electrical breakdown. Engineering of both interface domains in amorphous TiO2-based RRAM devices makes it possible that the devices are operated at any configuration of metal electrodes. By inserting an active thin metal layer at the top interface and embedding an Al2O3 blocking layer at the bottom interface, enhanced memory properties can be obtained compared to the conventional Al/a-TiO2/Al devices.