Strong Charge Retention via Surface Oxygen Vacancies of LaAlO₃ Thin Films

Charge storage techniques are essential in a wide range of electronic applications, such as charge-trapping memory, controllable electret, and energy harvesting devices. The charge storage techniques are based on the strong charge localization in dielectric oxide materials. Thus, it is important to fully understand the underlying physics of charge localization in oxides and thereby develop optimal charge storage materials for practical applications. In this work, we demonstrate a strong charge retention behavior in single-crystalline LaAlO₃ (LAO) thin films. We show that the charges injected to the surface of LAO thin films survive for over 7 days with minimal degradation. Our Kelvin probe force microscopy (KPFM) analyses directly show that the dispersion of the surface-injected charges is extremely slow in LAO thin films compared to other similar perovskite oxide thin films. This long-term charge retention behavior in LAO can be explained by the characteristic distribution of oxygen vacancies governed by the internal polar field. Our results provide insight into developing electronically-controllable charge storage materials, which are suitable for advanced electret and charge-trapping memory applications.