Forming-Free One-Selector/One-Resistor Characteristics of Oxygen-Rich ITO Based Transparent Resistive Switching Memory via Defect Engineering Using the Reactive Sputtering Process

In recent research of resistive random access memory (RRAM), solving the degradation phenomenon induced by both a high forming voltage to form the conducting filaments (CFs) and a high reset current is one of the main issues encountered. In this study, to overcome these problems, we propose forming-free bipolar resistive switching (BRS) behaviors by employing an ITO film with abundant oxygen vacancies, instead of conventional CF based RRAM requiring a forming process, and systematically investigate the feasibility of forming free BRS behaviors and a possible switching mechanism. Compared to conventional CF based RRAM devices, it is possible for the proposed devices to achieve stable BRS properties (i.e., narrow variations of operating current and voltage, and retention) without the forming process, under an operating current of sub-nano ampere. In addition, the proposed cell shows a stable hysteresis of current–voltage curves, which is well matched with the Poole-Frenkel emission, and currents at a low voltage are limited due to a formed barrier height like Schottky diode between the active layer and electrodes.