Electroforming-Free, Flexible, and Reliable Resistive Random-Access Memory Based on an Ultrathin TaO_x Film

A flexible resistive switching (RS) memory was fabricated on a Ta/TaOx/Pt/polyimide (PI) structure with various TaOx thicknesses (5, 10, and 15 nm). The oxygen vacancy (VO) concentrations in the TaOx films were also adjusted by controlling the oxygen partial pressure during TaOx deposition to obtain different electroforming (EF) behaviors. When the devices of Ta/TaOx/Pt/PI showed the EF-free characteristic, the reliability and endurance performance were greatly improved compared to those of devices with EF behavior. The resistive crossbar array using the thinnest (5 nm) TaOx film showed high uniformity and endurance performance up to 108 switching cycles even after bending to a 2 mm radius 10 000 times. However, for the EF samples, the endurance performance was much lower and involved the reset failure, even with the 5 nm TaOx film.