Study of radiation hardness of HfO2-based resistive switching memory at nanoscale by conductive atomic force microscopy

A resistive switching random access memory (RRAM) with an HfO₂/Ti structure grown on a molybdenum (MO) substrate was fabricated, and a gold (Au) conductive atomic force microscopy (CAFM) tip was used as the top electrode such that the cell area of the resulting RRAM device is as small as 3 × 10⁻¹² cm². The pre- and post-irradiated resistive switching behaviors of the RRAM device with various HfO₂ layer thicknesses were investigated after being subjected to Co⁶⁰ γ-ray irradiation with different radiation doses. It is found that the forming voltage (V_forming), set voltage (V_set), resistance of high resistance state (RHRS) and resistance of low resistance state (RLRS) of the RRAM device are all radiation dose-dependent. The V_forming, V_set, RHRS and RLRS all decrease as the radiation dose increases due to increasing radiation-induced oxygen vacancies or defects inside the HfO₂ layer. Our experimental results indicate that the HfO₂-based RRAM cell with an extremely small cell area is not actually radiation hard since the operating voltage will change with V_forming and V_set after irradiation.