Bipolar Resistive Switching in Forming-Free, Flexible and Transparent ReRAM for Wearable Applications

Resistive Random Access Memory (ReRAM) is an emerging class of non-volatile memory that stores information by changing the resistance of a material within its memory cells. Unlike conventional memory technologies, ReRAM uses applied voltage to change the resistance in a metal oxide layer (generally metal oxide), representing binary states (0 or 1) for data storage. This switching behavior typically involves movement of ions, vacancies, or defects within the oxide layer, creating conductive paths or disrupting them based on the applied voltage polarity. In this study, we introduce a flexible, forming-free ReRAM device using an aluminium-doped zinc oxide (AZO) electrode paired with a nickel oxide (NiO) active layer. The fabricated Ti/NiO/AZO/PET device exhibits reliable bipolar resistive switching (BRS) with two distinct and stable resistance states, which are critical for neuromorphic computing applications. Electrical analysis confirmed stable high and low resistance states, with set voltage (V_SET) around 5.4V and reset voltage (V_RESET) around 2.9V, achieving over 300 endurance cycles and retention times around 1,000 seconds. Different conduction mechanisms were observed for the high resistance state (HRS) and low resistance state (LRS), such as ohmic behavior and space charge limited current (SCLC). Under bending conditions, electrical analysis demonstrated consistent performance and stability, with minimal changes in V_SET and V_RESET. These findings suggest the suitability of NiO/AZO-based flexible ReRAM for applications in high-density data storage and wearable electronics.