Dielectric and optical constants of nanostructured (Pb0.7Sr0.3)TiO3 thin films suitable for high frequency devices

摘要

Polycrystalline grains in a nano-scale of (Pb0.7Sr0.3) TiO3 (PST) thin film have been synthesized by the metallo-organic decomposition technique. The PST films were deposited on Pt/Ti/SiO2/Si and fused quartz substrates by the spin coating technique and annealed at different temperatures of 650 and 750 degrees C to get the crystalline phase. The effect of Sr content to reduce the grain size in PST films has been observed. The x-ray diffraction shows that the PST film exhibits a distorted tetragonal single phase. Atomic force microscopy shows that the grain size increases with increasing annealing temperature. The average grain size is observed as 38 nm and 47 nm, respectively, for the film annealed at 650.C and 750 degrees C. The dielectric relaxations are stabilized up to a higher frequency region of 12MHz and a larger value of dielectric constant with low loss is observed for the film annealed at 650.C than that at 750 degrees C. The optical constants such as refractive index (n), extinction coefficient (k), energy band gap, optical dielectric constant and conductivity have been calculated from the transmission spectrum in the wavelength range 300-1100 nm. The optical constants are compared and in good agreement with the Wemple-DiDomenico single oscillator model. These nanostructured PST thin films exhibit electrical as well as optical constants up to a higher frequency region.