Structural properties and electroforming-free resistive switching characteristics of GdOx, TbOx, and HoOx memory devices

Resistive random access memory (RRAM) using the Ru/REOx/TaN (rare-earth, RE, RE = Gd, Tb and Ho) structures is fabricated with full room temperature process and is not required the electroforming process. X-ray diffraction and X-ray photoelectron spectroscopy were used to study the structural and chemical features of REOx films. The conduction mechanism of REOx-based RRAM memory devices in the low-resistance state is Ohmic emission, whereas the high-resistance state is space-charge-limited conduction. The GdOx-based RRAM devices show high-resistance ratio of about 104, reliable data retention of 105 s, and stable cycling behaviors for up to 190 cycles. This result suggests the high concentration of the metallic Gd0 and oxygen vacancies in GdOx film. The Ru/GdOx/TaN structure memory is a possible candidate for next-generation nonvolatile memory applications.