Effect of phase transformation on optical and dielectric properties of pulsed laser deposited ZnTiO_3 thin films

摘要

Zinc titanate (ZnTiO_3) ceramics were prepared by conventional solid state reaction method using ZnO and TiO_2 in a molar ratio of 1:1 with optimized parameters. It was found that the sample sintered at 800 ℃ for 12 h exhibit single hexagonal phase of ZnTiO_3. ZnTiO_3 thin film have been deposited on ITO coated glass substrate using pulsed laser deposition (PLD) technique employing a KrF laser source (λ = 248 nm). In present work, the effect of substrate temperature, which leads to transformation of hexagonal phase to cubic phase, has been studied. The XRD pattern revealed that pure hexagonal phase of ZnTiO_3 appear upto 400 ℃ and more increment in substrate temperature leads to transformation of hexagonal phase to cubic phase. We have observed the blue shift in absorption edge at lower temperature. When the substrate temperature increases from 300 to 400 ℃ the band gap decreases due to strong hexagonal phase, but more increment in substrate temperature increases the band gap causes by change of phase from hexagonal to cubic. The dielectric constant of ZnTiO_3 thin film increases as the substrate temperature increases due to the enhancement in crystallinity and improved morphology.