LAUSR

In this article, (Al1−0.02−xSi0.02Tix)2Oy (x = 0.2, 0.9 and 2%) thin films were prepared on Pt/Ti/SiO2/Si substrates using sol–gel technique. The dielectric properties of undoped and Si–Ti co-doped Al2O3 thin films were investigated. The leakage current of (Al0.971Si0.02Ti0.009)2Oy thin film is reduced by 2 orders of magnitude compared with Al2O3 film. Meanwhile, the modified sample exhibits the ultrahigh energy density of 14.01 J/cm3 under the breakdown strength of 647 MV/m, which is an enhancement of 11.26 J/cm3 over that of the undoped Al2O3 film. The improvement of dielectric properties is ascribed to the forming of Al–O–Si, Al–O–Ti bonds and the anodic oxidation of Ti3+, which could strengthen the stability of Al2O3 structure and self-repair the defects of the films under applied electric field. Another reason is that cation vacancies generated by Si–Ti co-doping could effectively prevent the formation of oxygen vacancies and decrease the breakdown probability of the films. This work provides a promising route to dielectric thin films materials for electrical energy storage applications.