Structure and voltage tunable dielectric properties of sol–gel derived Bi1.5MgNb1.5O7 thin films

Abstract

Bi1.5MgNb1.5O7 (BMN) thin films were fabricated on Au/Ti/SiO2/Si(100) substrates using a sol–gel spin coating process. Thermo decomposition of the BMN precursor gel was discussed. The structures, morphologies, dielectric properties and voltage tunable dielectric properties were investigated. The deposited films showed a cubic pyrochlore structure after annealing at 550 °C or higher temperatures. With the annealing temperature increased from 500 to 800 °C, the root-mean-square surface roughness of the films increased from 0.6 to 6.8 nm. Additional phase, MgNb2O6, emerged after annealing at 800 °C due to the volatilization of Bi element. The dielectric properties and tunability of the films were annealing temperature dependent. BMN thin films annealed at 750 °C had a high dielectric constant of 135 and low dielectric loss of 0.002 at 1 MHz. The high tunability of 31.3 % and figure of merit of 156.5 were obtained under an applied electric field of 1 MV/cm at room temperature.