High dielectric constant and energy density achieved in sandwich-structured SrTiO3 nanocomposite thick films by interface modulation

Abstract

An original design of sandwich-structured SrTiO₃ (STO) nanocomposite thick films has been achieved via a sol–gel based coating process. In that process, a pure STO amorphous film is set as the central layer and the STO composite films containing nanoparticle fillers and amorphous matrices are employed as two outer layers. It is revealed that the central amorphous layer with optimal thickness can permeate within the composite layer and effectively eliminate the interfacial structural defects (voids and cracks), giving rise to an increased dielectric constant. Additionally, the finite element simulation results show that the design of a sandwich structure is conducive to enhancing the E_b value of the nanocomposite films. It is because the middle amorphous layer could not only alleviate the high local electric field concentration caused by interface voids and cracks, but also lower the electric field in the outer composite layer to protect the sandwich-structured films from being broken down early. As a result, the sandwich-structured films reach the largest energy density of 10 J cm⁻³, which increases by 177% compared to the films without interface modulation (3.6 J cm⁻³).