Microstructure and dielectric properties of sputtered (Ba0.3Sr0.7)TiO3 thin films with amorphous interfacial layers

Crystallization behavior, microstructure and dielectric properties of sputtered (Ba0.3Sr0.7)TiO3 thin films have been studied. The crystallization from as-deposited amorphous structure to equilibrium crystalline structure is confirmed as an irreversible, exothermic and first-order transition by differential scanning calorimetry. At a heating rate of 20 degrees C/min, the exothermic peak temperature for crystallization is measured to be 697.3 degrees C. Transmission electron microscopy results reveal layered structures of amorphous and perovskite crystalline phases in the films deposited at temperatures between 450 and 650 degrees C. The amorphous interfacial layer diminishes with increasing substrate temperature and a well-crystallized film is found at 750 degrees C with a dielectric loss of 0.021. Dielectric constant shows an abrupt increase to 187 for the film deposited at 750 degrees C as a result of the fully crystallized structure. The measured dielectric constants at different temperatures are well consistent with those calculated based on the presence of amorphous interfacial layers in the films.