Functional behaviour of thin film dielectric superlattices

Abstract

Pulsed laser deposition has been used to fabricate thin film capacitor structures in which the dielectric layer is a superlattice. The properties of two superlattice systems were investigated as a function of superlattice wavelength Λ, one based on barium strontium titanate and the other on lead based relaxor electroceramics. In both systems the dielectric constant was significantly enhanced at stacking wavelengths of a few unit cells. However, the dielectric enhancement seen in the barium strontium titanate superlattices was found to be due to Maxwell-Wagner effects, whereas in the relax or superlattices Maxwell-Wagner behaviour was not evident; rather, the dielectric enhancement was associated with the onset of polar coupling at around Λ=20 nm.