Charge transport and bipolar switching mechanism in a Cu/HfO₂/Pt resistive switching cell

Bipolar resistance switching characteristics are investigated in Cu/sputtered-HfO₂/Pt structure in the application of resistive random access memory (RRAM). The conduction mechanism of the structure is characterized to be SCLC conduction. The dependence of resistances in both high resistance state (HRS) and low resistance state (LRS) on the temperature and device area are studied. Then, the composition and chemical bonding state of Cu and Hf at Cu/HfO₂ interface region are analyzed by x-ray photoelectron spectroscopy (XPS). Combining the electrical characteristics and the chemical structure at the interface, a model for the resistive switching effect in Cu/HfO₂/Pt stack is proposed. According to this model, the generation and recovery of oxygen vacancies in the HfO₂ film are responsible for the resistance change.