Enhancement of energy storage density achieved in Bi-modified SrTiO3 thin films by introducing a TiO2 layer

Abstract Dielectric Sr0.88Bi0.08TiO3 (SBT) and Sr0.88Bi0.08TiO3/TiO2 (SBT/TiO) thin films were fabricated via sol-gel and spin-coating method with various annealing temperatures ranging from 450 °C to 600 °C. The XRD results show that the SBT thin films can crystallize at a lower temperature due to introducing a TiO2 layer. The SEM results reveal that the annealing temperatures have impact on the surface morphology. Moreover, the absorbed water was closely related with annealing temperature. When the temperature rises to 550 °C, the reduction of absorbed water limited the formation of the aluminum oxide insulating layer between the Al electrode and the thin films, decreasing the breakdown strength. The finite element simulation showed the effect of the aluminum oxide insulating layer on enhancing the dielectric breakdown strength of the samples. The excellent energy storage performance was achieved in the SBT/TiO films annealed at 450 °C with the recoverable energy storage density of 31.3 J/cm3 and ultrahigh efficiency of 96%, which is almost 2 times that of SBT thin films (12.4 J/cm3). Additionally, the samples possess a high dielectric constant (107) and a low dissipation factor (~0.035) at 1 MHz. Therefore, This work could provide a novel and simple way to develop high-performance dielectric capacitor devices.