Microwave dielectric relaxation of the polycrystalline ( Ba , Sr ) Ti O 3 thin films

The microwave dielectric properties of the ( Ba , Sr ) Ti O 3 thin films annealed at various oxygen pressures ranging from 5 to 500 mTorr were investigated over the frequency range 0.5 - 5 GHz using a circular-patch capacitor geometry. The dielectric constant ( ε ) followed Curie-von Schweidler relaxation in the microwave-frequency range, and the degree of relaxation corresponded qualitatively with the measured dielectric loss ( tan δ ) . As the oxygen pressure varied, the dielectric loss had a maximum value of ∼ 0.03 at 100 mTorr , and its behavior was correlated with the Raman strength of the polar modes.