High Resistive Switching On/Off Ratio in Lu-Doped Hf0.4Zr0.6O2 Thin Films via Band Structure and Oxygen Vacancy Co-Strategy
Fluorite-structured oxides (HfO2, ZrO2) are promising for resistive random-access memory (RRAM) due to their scalability and tunable properties. However, achieving high resistive switching on/off ratios remains challenging. Here, we report a collaborative strategy combining Hf/Zr ratio optimization and Lu3+ doping to regulate band structure and oxygen vacancy concentration in Hf0.4Zr0.6O2 (LHZO) thin films. The resulting LHZO devices exhibit a resistive switching ratio of 8.4 × 10^4, two orders of magnitude higher than that of ZrO2 (1.2 × 10^3). Electrical characterization and synchrotron radiation photoemission spectroscopy reveal that Lu doping widens the bandgap to 4.95 eV, downshifts the valence band, and introduces defect states, collectively suppressing p-type conductivity and reducing off-state leakage current. Simultaneously, Lu3+ doping enriches oxygen vacancies, stabilizing ohmic conductive filaments in the on-state. This co-optimization of band structure and oxygen vacancies effectively enhances insulating properties in the high-resistance state and ohmic conductivity in the low-resistance state, leading to superior resistive switching performance with robust retention (>10^4 s). Our findings establish a fundamental strategy for tailoring electronic properties of doped HfZrO2 thin films toward high-performance RRAM applications.