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

• We investigated the resistive switching behaviors of RRAM cell with extremely small area before and after γ-ray irradiation.
• Forming voltage, set voltage, resistance of high- and low-resistance states are all radiation dose-dependent.
• A comprehensive model was proposed to explain the changes in post-irradiated resistive switching behaviors.

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 (Vforming), set voltage (Vset), resistance of high resistance state (RHRS) and resistance of low resistance state (RLRS) of the RRAM device are all radiation dose-dependent. The Vforming, Vset, 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 Vforming and Vset after irradiation.