Tunable dielectric properties of sol-gel derived (Pb_(0.35), Sr_(0.65)) (Zr_(0.5), Ti_(0.5))O_3 thin films for microwave application

摘要

Ferroelectric (Pb_(0.35)Sr_(0.65))(Zr_(0.5)Ti_(0.5))O_3 material with Curie temperature below room temperature was prepared by solution-gelation method on platinized silicon substrates. Structural and morphological evolution of the spin-coated films on Pt/ZrO_2/SiO_2/Si substrates as a function of annealing temperature were studied by X-ray diffraction and atomic force microscopy, respectively. Fully crystallized film with perovskite structure was obtained at an annealing temperature of 600 °C. Root-mean-square roughness of the 300 nm film was around 4.5 nm, manyfold higher than the underlying Pt substrate (～ 1 nm). Electrical properties of the fully crystallized films were studied as functions of frequency and temperature with an impedance analyzer. Dielectric constant and loss tangent were around 200 and 0.02, respectively, at a frequency 100 kHz. Dielectric tunability of the films with bias voltage and frequencies was studied and 45% tunability obtained at 500 kV/cm. The quality factor or the figure of merit of the (Pb_(0.35)Sr_(0.65))(Zr_(0.5)Ti_(0.5))O_3 films were determined from the tunability /loss tangent ratio and found to be 16 at 500 kV/cm.