I-V characteristics of Pt/HfO2/YBa2Cu3O7-x heterostructures

The resistance switching (RS) effect is one of the main research directions of the next generation of non -volatile memory devices. RS properties are mainly attained using different metallic or alloy electrodes; however, conductive oxides are also being investigated due to their excellent conductivity, thermal stability and oxidation resistance. Herein, a conductive oxide, i.e., YBCO, is used as an electrode for investigating the RS effect. The Pt/ HfO2/YBa2Cu3O7-x(YBCO) heterostructure is prepared using the pulsed laser deposition method, and the RS characteristics of HfO2 and the influence of oxygen ions (center dot O2- ) migration on YBCO resistance during the RS effect are systematically studied. First, the difference in the RS effect of HfO2 in the case of YBCO oxide electrode and Pt electrode is comparatively studied. It is found that the oxide electrode not only renders better oxidation resistance but also serves as the center dot O2- storage layer to promote the occurrence of RS effect, resulting in relatively low "Set" and "Reset" voltages. The mechanism of RS generation can be explained using the oxygen vacancies (OV2+) conductive filament (CF) model. The electrical transport characteristics of HfO2 mainly change from the Ohmic conduction mechanism to the space charge-limited current (SCLC) mechanism in the high-resistance state of HfO2, and mainly conforming to the SCLC mechanism in the low-resistance state of HfO2. With the decrease in temperature, the structure still demonstrates an obvious RS effect, and the resistance of high-resistance HfO2 and "Set" voltage of the RS effect increases slightly. Furthermore, during the RS process of HfO2, it is observed that the resistance of YBCO during the superconducting transformation process significantly increases under a positive bias voltage (YBCO with high potential) due to the migration and injection effects of center dot O2- . However, any significant change in YBCO resistance is not observed under the non-superconducting state and after superconducting transformation. At the same time, any change in YBCO resistance is not observed under a negative bias voltage. In addition, due to slight changes in the carrier concentration of YBCO, the magnetization curves of the Pt/HfO2/YBCO structure in HRS are slightly higher than LRS. These results provide experimental references for further research on the RS mechanism and development of adjustable devices.