Anodic formation of HfO2 nanostructure arrays for resistive switching application

Thin dielectric films are actively investigated as materials for novel resistive random-access memories based on resistive switching effect in metal/insulator/metal structures. Thin HfO2 films are of particular interest due to the high thermal stability, low operating voltages of resulting devices, and complementary metal-oxide-semiconductor technology compatibility of this material. In this study, we investigate the resistive switching behavior of nanostructured HfO2 film embedded in a porous anodic alumina matrix. The film was synthesized via self-organized electrochemical anodizing of a sputter-deposited Al/Hf bilayer on a Si substrate in an oxalic acid solution. The film was investigated by scanning electron microscopy. Simple metal/insulator/metal devices were prepared by sputter-deposition of Pt top electrodes through a shadow mask onto the nanostructured film. Assembled devices were characterized by I-V measurements. A bipolar eight-wise resistive switching was obtained, demonstrating a highly repeatable and stable low-voltage behavior in a set potential range. The achieved results indicate the high potential of the anodizing technique as an alternative to commonly used methods for producing insulating thin films for resistive random-access memory application.