Bias application hard x-ray photoelectron spectroscopy study of forming process of Cu/HfO2/Pt resistive random access memory structure

Abstract

The forming process of Cu/HfO2/Pt, which is an oxide based resistive random access memory (ReRAM), structure that exhibited resistance switching behavior at a voltage of 1.3 V was investigated by hard x-ray photoelectron spectroscopy under bias operation. A bias application to the structure reduced the Cu2O bonding state at the interface and the intensity ratio of Cu 2p3/2/Hf 3d5/2, providing the evidence of Cu2O reduction and Cu diffusion into the HfO2 layer. We directly observed Cu diffusion at the Cu/HfO2 interface under device operation, which is the evidence of the metal filament formation in the oxide-based ReRAM.