Exploring the Physical Properties Related to Resistive Switching Events in HfO₂-Based RRAM Devices with an Analytical Framework

Abstract

Herein, the physical properties of HfO 2 thin films such as crystal structure, chemical composition, transmissivity, and bandgap along with a comprehensive analytical model are investigated for resistive switching applications. The XPS measurements confirm the atomic percentage of 34.55% and 65.45% for hafnium and oxygen in the sputtered thin layer. The nonlattice oxygen in the oxide layer indicates the switching potential. Furthermore, the amorphous structure of the deposited HfO 2 film is ensured from XRD scanning. The UV−vis spectroscopy study suggests a high transmittance of ∼91% in visible range with a direct bandgap of 5.6 eV. The electrical characterization of fabricated Cu/HfO 2 /W RRAM devices demonstrates largely Ohmic and partly space charge limited conduction with bipolar switching events at V SET = 0.6 V and V RESET = −0.6 V. An analytical model incorporating key physical processes such as filament growth/shrinkage and local temperature rise is engaged to demonstrate and validate the switching events. With an applied voltage, the local temperature rises from room temperature to 729 K, with simultaneous filament radial growth up to 5 nm. Moreover, the power signature is calculated, where an inverse correlation is observed between the activation power and device resistance during switching events, which is validated with the experimental data. These findings will be helpful for the development of HfO 2 -based RRAM devices for emerging memory applications.