Dielectric properties of Ba_0.6Sr_0.4TiO₃ thin films deposited by mist plasma evaporation using aqueous solution precursor

Mist plasma evaporation (MPE) technique has been developed to deposit Ba_0.6Sr_0.4TiO₃ (BST) thin films on SiO₂/Si and Pt/Ti/SiO₂/Si substrates at atmospheric pressure using metal nitrate aqueous solution as precursor. MPE is characterized by the injection of liquid reactants into thermal plasma where the source materials in the droplets are evaporated by the high temperature of the thermal plasma. Nanometer-scale clusters are formed in the tail flame of the plasma, and then deposited and rearranged on the substrate at a lower temperature. Due to the high temperature annealing process of the thermal plasma before deposition, well-crystallized BST films were deposited at substrate temperature of 630 °C. The dielectric constant and dielectric loss of the film at 100 kHz are 715 and 0.24, respectively. Due to the good crystallinity of the BST films deposited by MPE, high dielectric tunability up to 39.3% is achieved at low applied electric field of 100 kV cm^-1.